The 1999 Mw 7.6 Chi\u2010Chi earthquake struck central Taiwan at 01:47 a.m. local time on 21 September 1999, as one of the most devastating natural disasters in Taiwan’s history and the largest instrumentally recorded event in the country (Shin and Teng, 2001). Its intense ground shaking, extended surface rupture, and widespread damage provided an unprecedented dataset that has profoundly shaped our understanding of fault mechanics and earthquake hazards in active collision zones (e.g., Kao and Chen, 2000; Ma et al., 2006).
", "doi": "10.1785/0120250259", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2026-02", "series_number": "1", "volume": "116", "issue": "1", "pages": "1-4" }, { "id": "authors:0pf2h-mct48", "collection": "authors", "collection_id": "0pf2h-mct48", "cite_using_url": "https://authors.library.caltech.edu/records/0pf2h-mct48", "type": "article", "title": "Supershear Earthquakes: Their Occurrence and Importance for Seismic Hazard, Early Warning, and Design Standards", "author": [ { "family_name": "Elbanna", "given_name": "Ahmed" }, { "family_name": "Abdelmeguid", "given_name": "Mohamed", "orcid": "0000-0002-3985-1721", "clpid": "Abdelmeguid-Mohamed" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Tainpakdipat", "given_name": "Napat", "orcid": "0009-0007-1681-8957" }, { "family_name": "Lavrentadis", "given_name": "Grigorios", "orcid": "0000-0001-6546-1340", "clpid": "Lavrentadis-Grigorios" }, { "family_name": "Rosakis", "given_name": "Ares", "orcid": "0000-0003-0559-0794", "clpid": "Roaskis-A-J" }, { "family_name": "Ben-Zion", "given_name": "Yehuda", "orcid": "0000-0002-9602-2014" } ], "abstract": "Strike-slip faults—where tectonic plates grind past each other horizontally—are a defining feature of many densely populated continental seismic zones worldwide, including the San Andreas fault system in California, the North and East Anatolian faults in Türkiye, and the Sagaing fault in Myanmar (Burma). Although their lateral motion has long been recognized, a growing body of global evidence is now highlighting a more hazardous aspect of these systems: supershear earthquakes—fast propagating ruptures that exceed the speed of shear waves and can cause disproportionately intense shaking and destruction. Four of the last six Mw 7.0+ earthquakes on strike-slip faults have been recognized as supershear events, including the damaging Mw 7.7 Myanmar and the Mw 7.8 Pazarcik earthquakes, highlighting the need to confront the potential implications of such future events.
", "doi": "10.1785/0220250118", "issn": "0895-0695", "publisher": "Seismological Society of America", "publication": "Seismological Research Letters", "publication_date": "2025-11", "series_number": "6", "volume": "96", "issue": "6", "pages": "3319-3323" }, { "id": "authors:s2hzj-jvp32", "collection": "authors", "collection_id": "s2hzj-jvp32", "cite_using_url": "https://authors.library.caltech.edu/records/s2hzj-jvp32", "type": "article", "title": "Effects of Near-Fault Sedimentary Rocks and Damage on the 2019 Ridgecrest, CA Earthquake: A Rupture Impediment or a Ground Motion Booster?", "author": [ { "family_name": "Oral", "given_name": "Elif", "orcid": "0000-0003-1081-5580", "clpid": "Oral-Elif" }, { "family_name": "Ampuero", "given_name": "Jean Paul", "orcid": "0000-0002-4827-7987" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "Observations of the 2019 magnitude 7.1 Ridgecrest, California, earthquake indicate a relatively slow rupture (2 km/s). The fault is surrounded by sedimentary rocks and low\u2010velocity damage zones, which can amplify ground motions but also slow down rupture. Here, we develop 3D dynamic rupture models to elucidate the significance of such effects on the Ridgecrest earthquake. We find that: (a) sedimentary rocks and damage, being shallow, do not explain the slow rupture but amplify slip and ground motion by more than a factor of 3; (b) accounting for ground motion amplification by sedimentary rocks improves the agreement with empirical predictions; (c) damage zone contributions to surface slip are minor (5%) for this event but could reach 25% in future southern California earthquakes. Our study corroborates the significance of source and site effects due to heterogeneous near\u2010fault materials during the Ridgecrest earthquake, and provides insights for future rupture and source\u2010to\u2010site hazard modeling efforts.
", "doi": "10.1029/2024gl112603", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2025-04-16", "series_number": "7", "volume": "52", "issue": "7", "pages": "e2024GL112603" }, { "id": "authors:nhpvy-xny69", "collection": "authors", "collection_id": "nhpvy-xny69", "cite_using_url": "https://authors.library.caltech.edu/records/nhpvy-xny69", "type": "article", "title": "Regional earthquake-induced landslide assessments for use in seismic risk analyses of distributed gas infrastructure systems", "author": [ { "family_name": "Ojomo", "given_name": "Olaide", "clpid": "Ojomo-Olaide" }, { "family_name": "Rathje", "given_name": "Ellen M.", "orcid": "0000-0002-4169-7153", "clpid": "Rathje-Ellen-M" }, { "family_name": "Wang", "given_name": "Pengfei", "orcid": "0000-0002-2844-4557", "clpid": "Wang-Pengfei" }, { "family_name": "Lavrendiatis", "given_name": "Greg", "orcid": "0000-0001-6546-1340", "clpid": "Lavrendiatis-Greg" }, { "family_name": "Zimmaro", "given_name": "Paolo", "orcid": "0000-0002-3544-5961", "clpid": "Zimmaro-Paolo" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Stewart", "given_name": "Jonathan P.", "orcid": "0000-0003-3602-3629", "clpid": "Stewart-Jonathan-P" } ], "abstract": "Earthquake-induced landslides are associated with significant risks to human lives and infrastructure. Spatially distributed infrastructure systems, such as pipelines, power lines, and transportation networks, are at particular risk to seismic landslides due to their large spatial extent. To conduct a comprehensive seismic landslide risk assessment for these systems, there is the need to evaluate the seismic landslide characteristics (i.e., location, size, displacement, direction) on a broad, regional scale. This paper presents a framework for seismic landslide analysis that provides this information for subsequent risk assessments. The approach computes seismic landslide displacements using a sliding block approach while accounting for the uncertainties in the input variables and displacement models using a logic tree. The computed displacements are then aggregated based on geomorphic landforms to define landslide zones. For each landslide zone, the statistical distributions of landslide features, such as landslide size, displacement level, and direction of movement, are defined. These attributes are presented in a format that can be integrated with fragility models for distributed infrastructure systems to quantify risk on a regional scale. The application of the approach is demonstrated through assessments for gas pipeline networks across the state of California in the United States.
", "doi": "10.1016/j.enggeo.2024.107664", "issn": "0013-7952", "publisher": "Elsevier", "publication": "Engineering Geology", "publication_date": "2024-10", "volume": "340", "pages": "107664" }, { "id": "authors:zhw0p-94q47", "collection": "authors", "collection_id": "zhw0p-94q47", "cite_using_url": "https://authors.library.caltech.edu/records/zhw0p-94q47", "type": "article", "title": "Broadband Ground-Motion Synthesis via Generative Adversarial Neural Operators: Development and Validation", "author": [ { "family_name": "Shi", "given_name": "Yaozhong", "orcid": "0000-0001-8863-2026", "clpid": "Shi-Yaozhong" }, { "family_name": "Lavrentiadis", "given_name": "Grigorios", "orcid": "0000-0001-6546-1340", "clpid": "Lavrentiadis-Grigorios" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Ross", "given_name": "Zachary E.", "orcid": "0000-0002-6343-8400", "clpid": "Ross-Z-E" }, { "family_name": "Azizzadenesheli", "given_name": "Kamyar", "orcid": "0000-0001-8507-1868", "clpid": "Azizzadenesheli-Kamyar" } ], "abstract": "We present a data\u2010driven framework for ground\u2010motion synthesis that generates three\u2010component acceleration time histories conditioned on moment magnitude (M), rupture distance (\u2060R_(rup)), time\u2010average shear\u2010wave velocity at the top 30 m (\u2060V_(S30)\u2060), and style of faulting. We use a Generative Adversarial Neural Operator (GANO)—a resolution invariant architecture that guarantees model training independent of the data sampling frequency. We first present the conditional ground\u2010motion synthesis algorithm (cGM\u2010GANO) and discuss its advantages compared to the previous work. We next train cGM\u2010GANO on simulated ground motions generated by the Southern California Earthquake Center Broadband Platform (BBP) and on recorded the Kiban–Kyoshin network (KiK\u2010net) data, and show that the model can learn the overall magnitude, distance, and V_(S30) scaling of effective amplitude spectra (EAS) ordinates and pseudospectral accelerations (PSA). Results specifically show that cGM\u2010GANO produces consistent median scaling with the training data for the corresponding tectonic environments over a wide range of frequencies for scenarios with sufficient data coverage. For the BBP dataset, cGM\u2010GANO cannot learn the ground\u2010motion scaling of the stochastic frequency components (f > 1 Hz); for the KiK\u2010net dataset, the largest misfit is observed at short distances (\u2060R_(rup) < 50 km\u2060) and for soft\u2010soil conditions (\u2060V_(S30) < 200 m/s\u2060) due to the scarcity of such data. Except for these conditions, the aleatory variability of EAS and PSA are captured reasonably well. Finally, cGM\u2010GANO produces similar median scaling to traditional ground\u2010motion models (GMMs) for frequencies greater than 1 Hz for both PSA and EAS but underestimates the aleatory variability of EAS. Discrepancies in the comparisons between the synthetic ground motions and GMMs are attributed to inconsistencies between the training dataset and the datasets used in GMM development. Our pilot study demonstrates GANO’s potential for efficient synthesis of broadband ground motions.
\n\nThe analysis of soil–structure interaction (SSI) problems has been established successfully in recent decades. In particular, the solution in the frequency domain provides an exact and efficient method for computing the response of the coupled system. Despite this, the state of practice as a first attempt to incentivize time domain analyses compatible with standard finite element packages introduces the so-called dimensionless flexible-base frequency. This frequency, which depends solely on the structure-to-soil-period ratio, allows transforming the frequency domain analyses into time domain analyses using frequency-independent soil impedance values. However, if such frequency exists for the combined system, it must depend on several physical variables. In this work, we propose a supervised approach to obtain the flexible-base dimensionless frequency at which the frequency-independent soil impedance should be used. The analysis is carried out using five dimensionless parameters, and the importance of each one to the estimation of the dimensionless flexible-base frequency is investigated. We use an inverse problem based on ensemble Kalman inversion (EnKI) to obtain the optimal frequency of the interaction. The data obtained are then employed in a machine-learning framework to map a set of dimensionless parameters to such a frequency. The generated mapping is finally verified, and a significant improvement in time-domain simulations is shown compared to the state of practice.
\nThe spatial distribution of horizontally buried structures makes them more susceptible to seismic hazards. This naturally requires a reliable and effective method to analyze soil-buried structure interaction (SbSI) problems, in which the reduced-order model is widely-used thanks to its robustness and computational efficiency. However, for buried structures, no reduced-order model was capable of simultaneously capturing the frequency-dependent characteristics and the true nonlinear nature of the interaction forces. Accordingly, we proposed a dual frequency- and deformation-dependent macroelement model to investigate dynamic axial SbSI problems in the time domain. Novel uniaxial material models, such as Modified Bouc-Wen and Gyromass, were also implemented in OpenSees for the macroelement model development. Results of the proposed approach show good agreement with those of published experiments and finite element analyses. Finally, we present an illustrative example of a buried pipe subjected to spatially varying seismic ground motions. To highlight the importance of frequency- and deformation-dependent characteristics, we compared the results obtained from the proposed approach with those from a frequency-independent Kelvin-Voigt model. It is noticed that ignoring the frequency-dependency can lead to an underestimate of the axial strain envelope, e.g. up to 30% in the case of seismic excitation with a central frequency of 6 Hz.
", "doi": "10.1016/j.compgeo.2023.105773", "issn": "0266-352X", "publisher": "Elsevier", "publication": "Computers and Geotechnics", "publication_date": "2023-12", "volume": "164", "pages": "105773" }, { "id": "authors:1warb-p1711", "collection": "authors", "collection_id": "1warb-p1711", "cite_using_url": "https://authors.library.caltech.edu/records/1warb-p1711", "type": "article", "title": "Soil-Structure Interaction Effects on a Regional Scale through Ground-Motion Simulations and Reduced Order Models: A Case Study from the 2008 Mw\u00a05.4 Chino Hills Mainshock", "author": [ { "family_name": "Kusanovic", "given_name": "Danilo S.", "orcid": "0000-0002-0935-2577" }, { "family_name": "Taborda", "given_name": "Ricardo", "orcid": "0000-0003-0358-370X" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "We demonstrate the effects of soil–structure interaction (SSI) for three idealized building typologies on a regional scale, using a simulated earthquake scenario of the 2008 Mw 5.4 Chino Hills mainshock in southern California as an example. All the three buildings lie on shallow foundations, and they are subject to three-component simulated ground motions. To carry out this task, we develop a reduced order model (ROM) for each building typology that accounts for the effects of SSI on the building system in the time domain. We specifically use ensemble Kalman inversion (EnKI) to extract the soil impedance values from fully coupled soil–foundation–structure interaction simulations; and we interpolate the EnKI results to derive analytical functions that span the range of applicability of the soil impedance model. We then verify our ROMs by comparing results to fully coupled soil–foundation–structure interaction simulations, also known as direct modeling methods. We finally populate the simulation grid across southern California with the verified building ROMs, and interpret the responses in the form of maps that represent urban-scale effects of SSI on the seismic demand parameters such as maximum displacement, acceleration, and interstory drift. We also identify areas where the effects of SSI, given the resonant characteristics of a specific building, the foundation typology, and the local site conditions, lead to higher seismic demand relative to the fixed-base response.
", "doi": "10.1785/0120220241", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2023-12", "series_number": "6", "volume": "113", "issue": "6", "pages": "2557-2573" }, { "id": "authors:yaszx-nxa84", "collection": "authors", "collection_id": "yaszx-nxa84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230425-250392700.3", "type": "article", "title": "The 2022 Chihshang, Taiwan, Earthquake: Initial GEER Team Observations", "author": [ { "family_name": "Carey", "given_name": "Trevor J.", "orcid": "0000-0003-4729-6884", "clpid": "Carey-Trevor-J" }, { "family_name": "Mason", "given_name": "H. Benjamin", "orcid": "0000-0003-4279-2854", "clpid": "Mason-H-Benjamin" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Athanasopoulos-Zekkos", "given_name": "Adda", "orcid": "0000-0002-3785-9009", "clpid": "Athanasopoulos-Zekkos-Adda" }, { "family_name": "Garcia", "given_name": "Fernando E.", "orcid": "0000-0001-7993-0347", "clpid": "Garcia-Fernando-Estefan" }, { "family_name": "Gray", "given_name": "Brian", "clpid": "Gray-Brian" }, { "family_name": "Lavrentiadis", "given_name": "Grigorios", "orcid": "0000-0001-6546-1340", "clpid": "Lavrentiadis-Grigorios" }, { "family_name": "Nweke", "given_name": "Chukwuebuka C.", "orcid": "0000-0002-8939-571X", "clpid": "Nweke-Chukwuebuka-C" } ], "abstract": "We recently returned from a post-earthquake reconnaissance trip to Taiwan sponsored by the National Science Foundation\u2013funded Geoengineering Extreme Events Reconnaissance (GEER) Association. We studied the effects of the September 18, 2022 MW6.9 Chihshang, Taiwan earthquake. The earthquake occurred on the Central Range strike-slip fault, with the rupture direction extending north from the epicenter. Nearfield seismic stations measured peak ground accelerations (PGAs) exceeding 0.5g along the fault. Peak ground velocities (PGVs) increased in the direction of the rupture with average intensities of 8 cm/s near the epicenter, increasing along the fault to 89 cm/s\n at the northern terminus. The ground motion recordings of the east (approximately fault parallel) component indicated strong velocity pulses in the direction of the rupture (Fig. 1).", "doi": "10.1061/jggefk.gteng-11522", "issn": "1090-0241", "publisher": "ASCE", "publication": "Journal of Geotechnical and Geoenvironmental Engineering", "publication_date": "2023-05", "series_number": "5", "volume": "149", "issue": "5", "pages": "Art. No. 02823002" }, { "id": "authors:7hj13-cn952", "collection": "authors", "collection_id": "7hj13-cn952", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230613-724210400.1", "type": "article", "title": "A latent Gaussian process model for the spatial distribution of liquefaction manifestation", "author": [ { "family_name": "Bullock", "given_name": "Zach", "orcid": "0000-0002-8748-425X", "clpid": "Bullock-Zachary" }, { "family_name": "Zimmaro", "given_name": "Paolo", "orcid": "0000-0002-3544-5961", "clpid": "Zimmaro-Paolo" }, { "family_name": "Lavrentiadis", "given_name": "Grigorios", "orcid": "0000-0001-6546-1340", "clpid": "Lavrentiadis-Grigorios" }, { "family_name": "Wang", "given_name": "Pengfei", "orcid": "0000-0002-2844-4557", "clpid": "Wang-Pengfei" }, { "family_name": "Ojomo", "given_name": "Olaide", "clpid": "Ojomo-Olaide" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Rathje", "given_name": "Ellen M.", "orcid": "0000-0002-4169-7153", "clpid": "Rathje-Ellen-M" }, { "family_name": "Stewart", "given_name": "Jonathan P.", "orcid": "0000-0003-3602-3629", "clpid": "Stewart-Jonathan-P" } ], "abstract": "This paper presents a model for distributing zones of liquefaction and nonliquefaction for use in regional liquefaction risk analysis. There are two broad methodologies that have been used to evaluate liquefaction risk on the regional scale: (a) application of site-specific procedures using soil properties inferred from geology, or (b) application of geospatial proxies for liquefaction. The first approach will tend to predict similar liquefaction probabilities across broad areas with similar geology, water table depths, and shaking intensities. The second approach yields the probability of liquefaction, which can be interpreted as the portion of the area affected by liquefaction (%Aliq). Neither approach, however, gives an informed prediction of the spatial distribution of liquefaction and the resulting displacements, which are particularly important for assessments of seismic risk for spatially distributed infrastructure systems. We propose a methodology for incorporating spatial correlation into a geospatial proxy for liquefaction to create maps of liquefaction and nonliquefaction for a given earthquake scenario. First, we describe a latent Gaussian process that is assumed to govern the spatial distribution of liquefaction. Next, a database of empirical observations of liquefaction is used to obtain the coefficients that describe that latent Gaussian process. The proposed model yields random realizations of maps of liquefaction and nonliquefaction conditioned on a map of (%Aliq). Such maps can be used to constrain the area over which displacements are estimated using soil properties inferred from geology and are therefore a critical component in reducing bias in assessments of liquefaction risk at the regional scale.", "doi": "10.1177/87552930231163894", "issn": "8755-2930", "publisher": "Earthquake Engineering Research Institute", "publication": "Earthquake Spectra", "publication_date": "2023-05", "series_number": "2", "volume": "39", "issue": "2", "pages": "1189-1213" }, { "id": "authors:pgrpx-3we54", "collection": "authors", "collection_id": "pgrpx-3we54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230221-19480300.46", "type": "article", "title": "Seismo-VLAB: An open-source finite element software for seismic meso-scale simulations", "author": [ { "family_name": "Kusanovic", "given_name": "Danilo S.", "orcid": "0000-0002-0935-2577", "clpid": "Kusanovic-Danilo-S" }, { "family_name": "Seylabi", "given_name": "Elnaz", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-Elnaz-E" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "We present Seismo-VLAB (SVL), a new open-source, object-oriented finite element software designed to optimize meso-scale simulations in the context of structural and geotechnical engineering. To this end, state-of-the-art tools and parallel computing capabilities required for efficient modeling of soil\u2013structure interaction and wave propagation in heterogeneous half-spaces are included. For example, perfectly matched layer, domain reduction method, dynamic nonlinear solvers, cutting edge parallel linear system solvers, domain decomposition method, and a series of plasticity models are some of the features available in SVL. In this work, we present the numerical implementation and software structure so enthusiastic developers can contribute to this open-source project and showcase some software capabilities using an illustrative example.", "doi": "10.1016/j.softx.2022.101300", "issn": "2352-7110", "publisher": "Elsevier", "publication": "SoftwareX", "publication_date": "2023-02", "volume": "21", "pages": "Art. No. 101300" }, { "id": "authors:dktqa-8jx85", "collection": "authors", "collection_id": "dktqa-8jx85", "cite_using_url": "https://authors.library.caltech.edu/records/dktqa-8jx85", "type": "publication_erratum", "title": "Correction: Kathmandu Basin as a local modulator of seismic waves: 2-D modelling of non-linear site response under obliquely incident waves", "author": [ { "family_name": "Oral", "given_name": "Elif", "orcid": "0000-0003-1081-5580" }, { "family_name": "Ayoubi", "given_name": "Peyman", "orcid": "0000-0001-6795-4923", "clpid": "Ayoubi-Peyman" }, { "family_name": "Ampuero", "given_name": "Jean Paul", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Bonilla", "given_name": "Luis Fabian", "orcid": "0000-0001-6270-9822" } ], "abstract": "In the publication process of Oral et al. (2022), Fig. 2b was not reproduced correctly due to error on the publisher’s side. We provide the correct version of the figure in PNG format below.
", "doi": "10.1093/gji/ggac425", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2023-02", "series_number": "2", "volume": "232", "issue": "2", "pages": "1470-1470" }, { "id": "authors:4m6qm-40w63", "collection": "authors", "collection_id": "4m6qm-40w63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230404-258305700.9", "type": "article", "title": "Estimation of Soil-Structure Model Parameters for the Millikan Library Building Using a Sequential Bayesian Finite Element Model Updating Technique", "author": [ { "family_name": "Ebrahimian", "given_name": "Hamed", "orcid": "0000-0003-1992-6033", "clpid": "Ebrahimian-Hamed" }, { "family_name": "Taha", "given_name": "Abdelrahman", "orcid": "0000-0002-5069-8465", "clpid": "Taha-Abdelrahman" }, { "family_name": "Ghahari", "given_name": "Farid", "orcid": "0000-0002-3847-5277", "clpid": "Ghahari-Farid" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Taciroglu", "given_name": "Ertugrul", "orcid": "0000-0001-9618-1210", "clpid": "Taciroglu-Ertugrul" } ], "abstract": "We present a finite element model updating technique for soil\u2013structure system identification of the Millikan Library building using the seismic data recorded during the 2002 Yorba Linda earthquake. A detailed finite element (FE) model of the Millikan Library building is developed in OpenSees and updated using a sequential Bayesian estimation approach for joint parameter and input identification. A two-step system identification approach is devised. First, the fixed-base structural model is updated to estimate the structural model parameters (including effective elastic modulus of structural components, distributed floor mass, and Rayleigh damping parameters) and some uncertain components of the foundation-level motion. Then, the identified structural model is used for soil\u2013structure model updating wherein the Rayleigh damping parameters, the stiffness and viscosity of the soil subsystem (modeled using a substructure approach), and the foundation input motions (FIMs) are estimated. The identified model parameters are compared with state-of-practice recommendations. While a specific application is made for the Millikan Library, the present work offers a framework for integrating large-scale FE models with measurement data for model inversion. By utilizing this framework for different civil structures and earthquake records, key structural model parameters can be estimated from the real-world recorded data, which can subsequently be used for assessing and improving, as necessary, state-of-the-art seismic analysis and structural modeling techniques. This paper presents an effort towards using real-world measurements for large-scale FE model updating in the soil and structure, uniform soil time domain for joint parameter and input estimation, and thus paves the way for future applications in system identification, health monitoring, and diagnosis of civil structures.", "doi": "10.3390/buildings13010028", "issn": "2075-5309", "publisher": "MDPI", "publication": "Buildings", "publication_date": "2022-12-23", "volume": "13", "pages": "Art. No. 28" }, { "id": "authors:m9gfv-cdk36", "collection": "authors", "collection_id": "m9gfv-cdk36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221219-416589000.12", "type": "article", "title": "A Method to Generate Initial Fault Stresses for Physics-Based Ground-Motion Prediction Consistent with Regional Seismicity", "author": [ { "family_name": "Oral", "given_name": "Elif", "orcid": "0000-0003-1081-5580", "clpid": "Oral-Elif" }, { "family_name": "Ampuero", "given_name": "Jean Paul", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" }, { "family_name": "Ruiz", "given_name": "Javier", "clpid": "Ruiz-Javier" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "Near\u2010field ground motion is the major blind spot of seismic hazard studies, mainly because of the challenges in accounting for source effects. Initial stress heterogeneity is an important component of physics\u2010based approaches to ground\u2010motion prediction that represents source effects through dynamic earthquake rupture modeling. We hypothesize that stress heterogeneity on a fault primarily originates from past background seismicity. We develop a new method to generate stochastic stress distributions as a superposition of residual stresses left by the previous ruptures that are consistent with regional distributions of earthquake size and hypocentral depth. We validate our method on M_w 7 earthquake models suitable for California by obtaining a satisfactory agreement with empirical earthquake scaling laws and ground\u2010motion prediction equations. To avoid the excessive seismic radiation produced by dynamic models with abrupt arrest at preset rupture borders, we achieve spontaneous rupture arrest by incorporating a growth of fracture energy as a function of hypocentral distance. Our analyses of rupture and ground motion reveal particular signatures of the initial stress heterogeneity: rupture can locally propagate at supershear speed near the highly stressed areas; the position of high\u2010stress and low\u2010stress areas due to initial stress heterogeneity determines how the peak ground\u2010motion amplitudes and polarization spatially vary along the fault, as low\u2010stress areas slow down the rupture and decrease stress drop. We also find that the medium stratification in the fault zone amplifies fault slip and consequent ground motion, which requires understanding the interaction between site effects and rupture dynamics. Our approach advances our understanding of the relations between dynamic features of earthquake ruptures and the statistics of regional seismicity, and our capability to integrate information about regional seismicity into near\u2010field ground\u2010motion prediction.", "doi": "10.1785/0120220064", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2022-12-01", "series_number": "6", "volume": "112", "issue": "6", "pages": "2812-2827" }, { "id": "authors:vxn08-99g89", "collection": "authors", "collection_id": "vxn08-99g89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221024-225625834", "type": "article", "title": "Analytical 1D transfer functions for layered soils", "author": [ { "family_name": "Garcia-Suarez", "given_name": "Joaquin", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-Joaquin" }, { "family_name": "Gonz\u00e1lez-Carbajal", "given_name": "Javier", "orcid": "0000-0002-1379-0406", "clpid": "Gonz\u00e1lez-Carbajal-Javier" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "Transfer functions are constantly used in both Seismology and Geotechnical Earthquake Engineering to relate seismic ground motion at different depths within strata. In the context of diffusive theory, they also appear in the expression of the imaginary part of 1D Green's functions. In spite of their remarkable importance, their mathematical structure is not fully understood yet, except in the simplest cases of two or three layers at most. This incomplete understanding, in particular as to the effect of increasing number of layers, hinders progress in some areas, as researchers have to resort to expensive and less conclusive numerical parametric studies. This text presents the general form of transfer functions for any number of layers, overcoming the above issues. The mathematical structure of these transfer functions comes defined as a superposition of independent harmonics, whose number, amplitudes and periods we fully characterize in terms of the properties of the layers in closed-form. Owing to the formal connection between seismic wave propagation and other phenomena that, in essence, represent different instances of wave propagation in a linear-elastic medium, we have extended the results derived elsewhere, in the context of longitudinal wave propagation in modular rods, to seismic response of stratified sites. The ability to express the reciprocal of transfer functions as a superposition of independent harmonics enables new analytical approaches to assess the effect of each layer over the overall response. The knowledge of the general closed-form expression of the transfer functions allows to analytically characterize the long-wavelength asymptotics of the horizontal-to-vertical spectral ratio for any number of layers.", "doi": "10.1016/j.soildyn.2022.107532", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2022-12", "series_number": "Art.107532", "volume": "163", "issue": "Art.107532" }, { "id": "authors:hmv67-fg674", "collection": "authors", "collection_id": "hmv67-fg674", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220920-62768000", "type": "article", "title": "Kathmandu Basin as a local modulator of seismic waves: 2-D modelling of non-linear site response under obliquely incident waves", "author": [ { "family_name": "Oral", "given_name": "Elif", "orcid": "0000-0003-1081-5580", "clpid": "Oral-Elif" }, { "family_name": "Ayoubi", "given_name": "Peyman", "orcid": "0000-0001-6795-4923", "clpid": "Ayoubi-Peyman" }, { "family_name": "Ampuero Saenz", "given_name": "Jean Paul", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Bonilla", "given_name": "Luis Fabian", "orcid": "0000-0001-6270-9822", "clpid": "Bonilla-Luis-Fabian" } ], "abstract": "The 2015 M_W 7.8 Gorkha, Nepal earthquake is the largest event to have struck the capital city of Kathmandu in recent times. One of its surprising features was the frequency content of the recorded ground motion, exhibiting a notable amplification at low frequencies (< 2\u00a0Hz) and a contrasting depletion at higher frequencies. The latter has been partially attributed to the damper behaviour of the Kathmandu basin. While such weak high-frequency ground motion helped avoiding severe damage in the city, the catastrophic outcomes of earlier earthquakes in the region attest to a contrasting role of the Kathmandu basin as a broad-band amplifier, in addition to possible source effects. Given the possibility of future strong events in the region, our main objective is to elucidate the seismic behaviour of the Kathmandu basin by focusing on site effects. We numerically model 2-D P\u2013SV wave propagation in a broad frequency band (up to 10\u00a0Hz), incorporating the most recent data for the Kathmandu basin geometry, soil stratigraphy and geotechnical soil properties, and accounting for the non-linear effect of multidimensional soil plasticity on wave propagation. We find that: (1) the Kathmandu basin generally amplifies low frequency ground motion (< 2\u00a0Hz); (2) waves with large incidence angles relative to vertical can dramatically amplify the high frequency ground motion with respect to bedrock despite the damping effect of soil non-linearity and (3) the spatial distribution of peak ground motion amplitudes along the basin is highly sensitive to soil non-linearity and wave incidence (angle and direction), favouring larger values near the basin edges located closer to the source, as observed during the 2015 event. Our modelling approach and findings can support the ongoing resilience practices in Nepal and can guide future seismic hazard assessment studies for other sites that feature similar complexities in basin geometry, soil stratigraphy and dynamic soil behaviour.", "doi": "10.1093/gji/ggac302", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2022-12", "series_number": "3", "volume": "231", "issue": "3", "pages": "1996-2008" }, { "id": "authors:vew9z-q4277", "collection": "authors", "collection_id": "vew9z-q4277", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220803-536012000", "type": "article", "title": "Dynamic soil impedance functions for cylindrical structures buried in elastic half-space", "author": [ { "family_name": "Nguyen", "given_name": "Kien T.", "orcid": "0000-0001-5761-3156", "clpid": "Nguyen-Kien-T" }, { "family_name": "Kusanovic", "given_name": "Danilo S.", "orcid": "0000-0002-0935-2577", "clpid": "Kusanovic-Danilo-S" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "Spatially-distributed buried structures are highly susceptible to seismic ground motions. The macroscopic soil reactions to soil\u2013structure relative displacements, aka. soil impedance functions (SIFs) and represented by a set of springs and dashpots, are thus very important for the assessment and design of those systems. Previous models to investigate the interaction problems between soil and horizontally buried structures (such as pipelines, tunnels) have been using spring stiffness chosen as static or frequency-independent constants, ignoring the nature of seismic loading and the energy reflected from the ground free surface. This paper presents analytical solutions for computing the frequency-domain SIFs for an infinitely-long cylindrical structure buried horizontally in homogeneous elastic half-space. The main challenge lies in mixed-boundary-value condition, where displacements are prescribed at the circular soil\u2013structure interface and traction-free condition is satisfied along the straight-line ground surface. We used Hankel\u2013Fourier series expansion, image technique, and Graf's addition theorem to derive solution for axial SIFs. For a more complex in-plane SIFs problem, meanwhile, we used Hankel- and Bessel\u2013Fourier series expansion. The in-plane solution requires numerical evaluation of contour integrals on the physical Riemann sheet, thus nested Gauss\u2013Kronrod quadrature rule as well as Cauchy's residue theorem are employed. We then verified our analytical solutions using results obtained from finite element simulations, in which a perfect agreement is shown between two approaches. The half-space SIFs are shown to also converge to their full-space counterparts in case of large burial depth. Additionally, parametric study was conducted to examine the variation of frequency-dependent SIFs, normalized with soil shear modulus, in response to the changes in soil Poisson's ratio and the structure burial depth.", "doi": "10.1016/j.soildyn.2022.107431", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2022-11", "volume": "162", "pages": "Art. No. 107431" }, { "id": "authors:8pyya-jzy45", "collection": "authors", "collection_id": "8pyya-jzy45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220804-250008000", "type": "article", "title": "P- and S-wave velocity estimation by ensemble Kalman inversion of dispersion data for strong motion stations in California", "author": [ { "family_name": "Bas", "given_name": "Elif Ecem", "clpid": "Bas-Elif-Ecem" }, { "family_name": "Seylabi", "given_name": "Elnaz", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-Elnaz-E" }, { "family_name": "Yong", "given_name": "Alan", "orcid": "0000-0003-1807-5847", "clpid": "Yong-Alan" }, { "family_name": "Tehrani", "given_name": "Hesam", "clpid": "Tehrani-Hesam" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "This study uses an ensemble Kalman method for near-surface seismic site characterization of 154 network earthquake monitoring stations in California to improve the resolution of S-wave velocity (V_S) and P-wave velocity (V_P) profiles\u2014up to the resolution depth\u2014coupled with better quantification of uncertainties compared to previous site characterization studies at this network. These stations were part of the Yong et\u00a0al. site characterization project, with selected stations based on future recordings of ground motions that are expected to exceed 10\u00a0per\u00a0cent peak ground acceleration in 50\u00a0yr. To estimate V_S and V_P from experimental dispersion data, Yong et\u00a0al. investigated these stations using linearized (local search and iteration) routines, and Yong et\u00a0al. later studied a subset of these stations using nonlinear (global search and optimization) routines. In both studies, the selection of model parameters\u2014that is, discretization of the V_S and V_P profiles with only five fixed thickness layers\u2014was mainly based on trial and error. In contrast, this paper uses an approximate Bayesian method to assimilate experimental dispersion data and sequentially update an ensemble of particle estimates that span the V_S and V_P parameter spaces. Doing so, we systematically determine the most probable profiles conditioned on the experimental dispersion data, the introduced noise levels, and a priori knowledge in the form of physical constraints. We consider two configurations to discretize the soil depth from the surface to half of the maximum discernible wavelength obtained from the experimental dispersion data, namely refined and coarse models, and two initial models for each configuration to study solution multiplicity. Our results suggest that using the refined model for the top surface layers improves the resolution of near-surface site characteristics and the model's success rate in capturing dispersion data at high frequencies. All models result in similar VS but distinct VP profiles, with increasing uncertainty at deeper layers, suggesting that the fundamental mode of Rayleigh wave dispersion data is not adequate to constrain the P-wave velocity profile and the S-wave velocity close to the resolution depth.", "doi": "10.1093/gji/ggac201", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2022-10", "series_number": "1", "volume": "231", "issue": "1", "pages": "536-551" }, { "id": "authors:yr50h-zea54", "collection": "authors", "collection_id": "yr50h-zea54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220708-315781900", "type": "article", "title": "Three\u2010dimensional nonlinear soil\u2013structure interaction for Rayleigh wave incidence in layered soils", "author": [ { "family_name": "Nguyen", "given_name": "Kien T.", "orcid": "0000-0001-5761-3156", "clpid": "Nguyen-Kien-T" }, { "family_name": "Kusanovic", "given_name": "Danilo S.", "orcid": "0000-0002-0935-2577", "clpid": "Kusanovic-Danilo-S" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "We propose a methodology to analyze three-dimensional (3D) nonlinear soil\u2013structure interaction (SSI) problems for Rayleigh (R) wave incidence in horizontally layered soils. The methodology comprises of two steps: (i) we calculate the free-field displacement histories of the layered soil subjected to incident R wave using thin-layer method (TLM) and (ii) we compute the effective input forces using domain reduction method (DRM) and simulate the responses of the structure and its vicinity using finite element analysis. Through a comprehensive verification study, we find good agreement with published research on SSI problems that implement boundary elements in the free-field; as well as on layered media problems with no structures that implement the propagator matrix technique and TLM. The agreement is consistently good for homogeneous and layered soils in 2D and 3D. Finally, we illustrate the capability of the methodology through a nonlinear analysis of a 12-story building on a two-layer soil overlaying a homogeneous halfspace, subjected to R wave incidence. The presented example highlights the influence of incident wave azimuth on measures of the building response, such as peak acceleration, inter-story drift ratio, and rocking motions.", "doi": "10.1002/eqe.3700", "issn": "0098-8847", "publisher": "Wiley", "publication": "Earthquake Engineering and Structural Dynamics", "publication_date": "2022-09", "series_number": "11", "volume": "51", "issue": "11", "pages": "2752-2770" }, { "id": "authors:tqb67-jcz92", "collection": "authors", "collection_id": "tqb67-jcz92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220823-628154700.753", "type": "article", "title": "Application of ray methods to one-dimensional site response of inhomogeneous soil deposits", "author": [ { "family_name": "Garcia-Suarez", "given_name": "Joaquin", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-J" }, { "family_name": "Seylabi", "given_name": "Elnaz", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-Elnaz-E" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "The technique referred as ray approximation treats wave propagation in a heterogeneous medium at the infinitely small wavelength limit. This classic simplification allows useful approximate analytical results to be obtained in cases where complete description of the waveform behaviour is virtually unattainable, hence its wide use in physics. In seismology, this approximation has been widely applied. This paper presents an application in one-dimensional site response (1DSR) analysis: it is used herein, first to explain and elucidate the generality of some previous observations as to the use of the harmonic mean of a shear-wave velocity profile to represent the global behaviour of a site; and second to partially settle an open question in 1DSR, namely 'What are the equivalent homogeneous properties that yield the same response, in terms of natural frequencies and resonance amplitude, for a given inhomogeneous site?', providing a few assumptions are met \u2013 chiefly, that excitations of sufficiently high frequency are considered.", "doi": "10.1680/jgeot.21.00164", "issn": "0016-8505", "publisher": "ICE Publishing Ltd.", "publication": "G\u00e9otechnique", "publication_date": "2022-08-30" }, { "id": "authors:z6xhx-t7278", "collection": "authors", "collection_id": "z6xhx-t7278", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220616-956471100", "type": "article", "title": "Predicting V\u209a and constrained modulus reduction curve based on V\u209b and shear modulus reduction curve in accordance with poroelastic theory", "author": [ { "family_name": "Tsai", "given_name": "Chi-Chin", "orcid": "0000-0002-7900-9184", "clpid": "Tsai-Chi-Chin" }, { "family_name": "Liu", "given_name": "Hsing-Wen", "clpid": "Liu-Hsing-Wen" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "The compression wave velocity (V\u209a) of sediments plays a key role in seismic wave amplification of vertical motion and is required in site response analysis. However, such information is usually lacking during field exploration (e.g. the surface wave method) because only shear wave velocity (V\u209b) is obtained. This aim of this study is to predict V\u209a based on V\u209b empirically and theoretically, particularly focusing on saturated conditions. The empirical approach is to establish the V\u209a correlation dependency on Poisson's ratio and V\u209b, and the theoretical approach is based on poroelastic theory that accounts for the interaction between fluid and soil skeleton. The engineering geological database for the Taiwan strong motion instrumentation program and the Kiban Kyoshin network database in Japan are adopted to establish an empirical model and validate poroelastic theory. The validated poroelastic approach is used to develop a constrained modulus reduction curve dependency on the porosity, V\u209b, Poisson's ratio and degree of saturation with a shear modulus reduction curve. The proposed approach can be used to develop generic V\u209a profiles and constrained modulus reduction curves for the site response to vertical motion given a site-specific V\u209b profile.", "doi": "10.1680/jgeot.21.00143", "issn": "0016-8505", "publisher": "ICE Publishing Ltd.", "publication": "G\u00e9otechnique", "publication_date": "2022-06-22" }, { "id": "authors:h6c4h-7g059", "collection": "authors", "collection_id": "h6c4h-7g059", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220520-388187000", "type": "monograph", "title": "A method to generate initial fault stresses for physics-based ground motion prediction consistent with regional seismicity", "author": [ { "family_name": "Oral", "given_name": "Elif", "orcid": "0000-0003-1081-5580", "clpid": "Oral-Elif" }, { "family_name": "Ampuero", "given_name": "Jean Paul", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" }, { "family_name": "Ruiz", "given_name": "Javier", "clpid": "Ruiz-Javier-A" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "Near-field ground motion is the major blind spot of seismic hazard studies, mainly because of the challenges in accounting for source effects. Initial stress heterogeneity is an important component of physics-based approaches to ground motion prediction that represent source effects through dynamic earthquake rupture modeling. We hypothesize that stress heterogeneity on a fault primarily originates from past background seismicity. We develop a new method to generate stochastic stress distributions as a superposition of residual stresses left by previous ruptures that are consistent with regional distributions of earthquake size and hypocentral depth. We validate our method on M_w 7 earthquake models suitable for California, by obtaining a satisfactory agreement with empirical earthquake scaling laws and ground motion prediction equations. To avoid the excessive seismic radiation produced by dynamic models with abrupt arrest at preset rupture borders,\nwe achieve spontaneous rupture arrest by incorporating a scale-dependent fracture energy adjusted with fracture mechanics theory. Our analyses of rupture and ground motion reveal particular signatures of the initial stress heterogeneity: rupture can locally propagate at supershear speed near the highly-stressed areas; the position of high-stress and low-stress areas due to initial stress heterogeneity determines how the peak ground motion amplitudes and polarization spatially vary along the fault, as low-stress areas slows down the rupture, decrease stress drop, and change the radiation distribution before the rupture arrest. We also find that the medium stratification amplifies the moment rate spectrum at frequencies above 2 Hz, which requires understanding the interaction between site effects and rupture dynamics; therefore, we highlight the need to consider a realistic fault medium on future studies of rupture dynamics. Our approach advances our understanding of the relations between dynamic features of earthquake ruptures and the statistics of regional seismicity, and our capability to model source effects for near-field ground motion prediction studies.", "doi": "10.1002/essoar.10511188.2", "publication_date": "2022-04-26" }, { "id": "authors:wxn9d-5ya44", "collection": "authors", "collection_id": "wxn9d-5ya44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220517-740389000", "type": "monograph", "title": "Monte Carlo Simulation to Study the Spatial Variation of Ground Motion Associated with Basin Heterogeneities", "author": [ { "family_name": "Ayoubi", "given_name": "Peyman", "orcid": "0000-0001-6795-4923", "clpid": "Ayoubi-Peyman" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "Basin effects cause a complex wave interference inside a basin which can be attributed to basin versus bedrock material contrast and edge effect. This will have a significant impact on spatial variation, duration, and intensity of surface ground motion (SGM) during an earthquake. While important, the lack of sufficient information about material properties and stratigraphy of a basin prevents accurate simulation of the phenomena, particularly in high frequency regime. Stochastic analysis and the Monte Carlo technique are suitable approaches to address this issue, where basin material is represented by a correlated random field. In this study, We use a 2D finite element analysis of an idealized-shaped basin subjected to a vertically propagating SV plane wave and investigate the spatial variation of SGM associated with basin effects by assuming a correlated random field to represent basin material. We generate a random medium by adding perturbations to a homogeneous domain with various correlation lengths, coefficient of variations, and autocorrelation functions to evaluate their contribution to SGM. Our results show a difference between the output of homogeneous and stochastic models, where we conclude that the former would not represent basin response, especially in the high-frequency regime correctly. Among the parameters we consider, the coefficient of variation has the most influential impact on surface acceleration. We observe that increasing this parameter decreases the mean value of surface amplification while its standard deviation increases. In addition, correlation length affects the standard deviation of surface acceleration, but it does not significantly impact the mean amplification. As for the autocorrelation function, where we consider von Karman, Gaussian, and exponential, the results show that the trend of surface amplification does not change by choosing a different autocorrelation function. Finally, by comparing the 2D basin versus 1D layered medium, we show that one cannot accurately capture basin response by using a 1D analysis for seismic hazard quantification.", "doi": "10.31224/2285", "publication_date": "2022-04-18" }, { "id": "authors:9g4vh-9gc20", "collection": "authors", "collection_id": "9g4vh-9gc20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220823-628154700.754", "type": "article", "title": "Data-Driven Synthesis of Broadband Earthquake Ground Motions Using Artificial Intelligence", "author": [ { "family_name": "Florez", "given_name": "Manuel A.", "orcid": "0000-0003-1034-2082", "clpid": "Florez-Manuel-A" }, { "family_name": "Caporale", "given_name": "Michaelangelo", "clpid": "Caporale-Michaelangelo" }, { "family_name": "Buabthong", "given_name": "Pakpoom", "orcid": "0000-0001-5538-138X", "clpid": "Buabthong-Pakpoom" }, { "family_name": "Ross", "given_name": "Zachary E.", "orcid": "0000-0002-6343-8400", "clpid": "Ross-Z-E" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Meier", "given_name": "Men-Andrin", "orcid": "0000-0002-2949-8602", "clpid": "Meier-Men-Andrin" } ], "abstract": "Robust estimation of ground motions generated by scenario earthquakes is critical for many engineering applications. We leverage recent advances in generative adversarial networks (GANs) to develop a new framework for synthesizing earthquake acceleration time histories. Our approach extends the Wasserstein GAN formulation to allow for the generation of ground motions conditioned on a set of continuous physical variables. Our model is trained to approximate the intrinsic probability distribution of a massive set of strong-motion recordings from Japan. We show that the trained generator model can synthesize realistic three-component accelerograms conditioned on magnitude, distance, and V_(S30). Our model captures most of the relevant statistical features of the acceleration spectra and waveform envelopes. The output seismograms display clear P- and S-wave arrivals with the appropriate energy content and relative onset timing. The synthesized peak ground acceleration estimates are also consistent with observations. We develop a set of metrics that allow us to assess the training process's stability and to tune model hyperparameters. We further show that the trained generator network can interpolate to conditions in which no earthquake ground-motion recordings exist. Our approach allows for the on-demand synthesis of accelerograms for engineering purposes.", "doi": "10.1785/0120210264", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2022-04", "series_number": "4", "volume": "112", "issue": "4", "pages": "1979-1996" }, { "id": "authors:z2knf-1zv93", "collection": "authors", "collection_id": "z2knf-1zv93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211206-445261197", "type": "monograph", "title": "Analytical 1D transfer functions for layered soils", "author": [ { "family_name": "Garcia-Suarez", "given_name": "Joaquin", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-Joaquin" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "Transfer functions are constantly used in both Seismology and Geotechnical Earthquake Engineering to relate seismic displacement at different depths within strata. In the context of Diffusive Theory, they also appear in the expression of the imaginary part of 1D Green's functions. In spite of its remarkable importance, their mathematical structure is not fully understood yet, except in the simplest cases of two or three layers at most. This incomplete understanding, in particular as to the effect of increasing number of layers, hinders progress in some areas, as researchers have to resort to expensive and less conclusive numerical parametric studies. This text presents the general form of transfer functions for any number of layers, overcoming the above issues. Owing to the formal connection between seismic wave propagation and other phenomena that, in essence, represent different instances of wave propagation in a linear-elastic medium, one can extend the results derived elsewhere [Garcia-Suarez, Joaquin. 2021. \"Trace Spectrum of 1D Transfer Matrices for Wave Propagation in Layered Media.\" engrXiv. June 24. doi:10.31224/osf.io/ygt8z] in the context of longitudinal wave propagation in modular rods to seismic response of stratified sites. The knowledge of the general closed-form expression of the transfer functions allows to analytically characterize the long-wavelength asymptotics of the horizontal-to-vertical spectral ratio for any number of layers.", "doi": "10.31224/osf.io/n43cv", "publisher": "engrXiv", "publication_date": "2021-11-09" }, { "id": "authors:zp7aw-erw26", "collection": "authors", "collection_id": "zp7aw-erw26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220420-758142300", "type": "book_section", "title": "Regional-Scale Geohazards Evaluation for Risk Assessment of Natural Gas Storage and Transmission Infrastructure", "book_title": "Geo-Extreme 2021: Case Histories and Best Practices", "author": [ { "family_name": "Zimmaro", "given_name": "Paolo", "clpid": "Zimmaro-Paolo" }, { "family_name": "Wang", "given_name": "Pengfei", "clpid": "Wang-Pengfei" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Bullock", "given_name": "Zach", "orcid": "0000-0002-8748-425X", "clpid": "Bullock-Zach" }, { "family_name": "Rathje", "given_name": "Ellen M.", "clpid": "Rathje-Ellen-M" }, { "family_name": "Ojomo", "given_name": "Olaide", "clpid": "Ojomo-Olaide" }, { "family_name": "Donahue", "given_name": "Jennifer L.", "clpid": "Donahue-Jennifer-L" }, { "family_name": "Bozorgnia", "given_name": "Yousef", "orcid": "0000-0003-1773-2489", "clpid": "Bozorgnia-Yousef" }, { "family_name": "Mosleh", "given_name": "Ali", "clpid": "Mosleh-Ali" }, { "family_name": "Stewart", "given_name": "Jonathan P.", "clpid": "Stewart-Jonathan-P" } ], "contributor": [ { "family_name": "Meehan", "given_name": "Christopher L.", "clpid": "Meehan-Christopher-L" }, { "family_name": "Pando", "given_name": "Miguel A.", "clpid": "Pando-Miguel-A" }, { "family_name": "Leshchinsky", "given_name": "Ben A.", "clpid": "Leshchinsky-Ben-A" }, { "family_name": "Jafari", "given_name": "Navid H.", "clpid": "Jafari-Navid-H" } ], "abstract": "Within the State of California, an extensive infrastructure of storage facilities and transmission pipelines provides natural gas to residential and commercial customers. A project funded by the California Energy Commission is developing a tool to evaluate the risk of this infrastructure system to earthquake hazards. This tool will have modules that characterize various hazards, infrastructure component fragilities, and system level risk.", "doi": "10.1061/9780784483688.008", "isbn": "9780784483688", "publisher": "American Society of Civil Engineers", "place_of_publication": "Reston, VA", "publication_date": "2021-11-04", "pages": "83-89" }, { "id": "authors:sa10w-7na17", "collection": "authors", "collection_id": "sa10w-7na17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200220-133401533", "type": "article", "title": "Optimization of frequency domain impedances for time-domain response analyses of building structures with rigid shallow foundations", "author": [ { "family_name": "Kusanovic", "given_name": "Danilo S.", "orcid": "0000-0002-0935-2577", "clpid": "Kusanovic-Danilo-S" }, { "family_name": "Seylabi", "given_name": "Elnaz E.", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-Elnaz-E" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "The effects of dynamic soil\u2013structure interaction (SSI) have been extensively studied in the last few decades, and proper analysis for the linear elastic case in frequency domain has been established successfully. However, SSI is rarely considered in the design of building structures, and instead, buildings are frequently analyzed using a rigid base assumption and quasi-static loading conditions that ignore SSI and its dynamic nature. Acknowledging these shortcomings, the National Institute of Standards and Technology (NIST) published in 2012 a set of recommendations on time-domain analyses of SSI for building structures compatible with standard finite element packages for consideration in engineering design. The so-called NIST GCR 12-917-21 report introduced a major simplification to enable frequency domain tools to be implemented in time domain analyses. That is, replacing the frequency-dependent soil impedance functions by a single-valued functions read at the flexible-base structure frequency; This work seeks to quantify the accuracy of this simplification considering fully coupled two-dimensional (2D) finite element models (FEM) as the reference. Using a Bayesian approach based on ensemble Kalman inversion (EnKI) and a range of numerical simulations of soil\u2013foundation\u2013building interaction, we estimate the optimal frequency that can be used to estimate soil impedance for time domain analyses; and we evaluate the improvement that the corresponding impedance offers relative to the full FEM results when compared to time domain analyses performed in accordance to the NIST recommendations outlined above.", "doi": "10.1177/8755293020981994", "issn": "8755-2930", "publisher": "Earthquake Engineering Research Institute", "publication": "Earthquake Spectra", "publication_date": "2021-08-01", "series_number": "3", "volume": "37", "issue": "3", "pages": "1955-1979" }, { "id": "authors:pnmxy-g7385", "collection": "authors", "collection_id": "pnmxy-g7385", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210216-140504716", "type": "article", "title": "Applications of the J-integral to dynamical problems in geotechnical engineering", "author": [ { "family_name": "Garcia-Suarez", "given_name": "J.", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-Joaquin" }, { "family_name": "Asimaki", "given_name": "D.", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Ortiz", "given_name": "M.", "orcid": "0000-0001-5877-4824", "clpid": "Ortiz-M" } ], "abstract": "We formulate a path-independent J-integral for the elastodynamic problem expressed in the frequency domain. We show that the path-independence of the integral can be exploited in order to derive ansatz-free identities and rigorous inequalities in certain problems arising in geotechnical engineering. By way of illustration, we specifically consider the problem of assessing seismic pressures on retaining walls. We show that the bounds for the earth thrust derived from the frequency-domain dynamic -integral improve upon previous heuristic and conjectured bounds.", "doi": "10.1016/j.jmps.2021.104353", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "2021-05", "volume": "150", "pages": "Art. No. 104353" }, { "id": "authors:h7tyf-0d502", "collection": "authors", "collection_id": "h7tyf-0d502", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210517-100803191", "type": "article", "title": "Seismic harmonic response of inhomogeneous soil: scaling analysis", "author": [ { "family_name": "Garcia-Suarez", "given_name": "Joaquin", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-Joaquin" }, { "family_name": "Seylabi", "given_name": "Elnaz", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-Elnaz-E" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "The study of the seismic response of inhomogeneous soil deposits, underlying rigid bedrock, has traditionally been framed as a one-dimensional wave propagation problem in a linear viscoelastic medium. When it comes to modelling soil inhomogeneity, the current trend to model the continuous variation of soil stiffness with depth employs a 'generalised parabolic function'. Exact solutions have already been obtained, but these come in terms of Bessel functions, which muddle the interpretation of results and obstruct assessment of the parameters' influence. This also hinders the definition of an 'equivalent homogeneous' soil deposit (a relevant concept utilised in many seismic codes). It is shown herein that the so-called inhomogeneity factor plays a secondary role in determining the response in many cases; thus straightforward guidelines are suggested for simplifying the problem, leading to elementary scaling relations. The scalings provide simple yet meaningful relations that reveal and explain the fundamental traits of the dynamic behaviour of these systems.", "doi": "10.1680/jgeot.19.p.042", "issn": "0016-8505", "publisher": "ICE Publishing Ltd.", "publication": "G\u00e9otechnique", "publication_date": "2021-05", "series_number": "5", "volume": "71", "issue": "5", "pages": "392-405" }, { "id": "authors:63mct-g3q07", "collection": "authors", "collection_id": "63mct-g3q07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200624-131552385", "type": "article", "title": "Linear one-dimensional site response analysis in the presence of stiffness-less free surface for certain power-law heterogeneities", "author": [ { "family_name": "Garcia-Suarez", "given_name": "Joaquin", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-Joaquin" }, { "family_name": "Seylabi", "given_name": "Elnaz", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-Elnaz-E" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "We revisit previous results in small-strain One-dimensional Site Response Analysis of heterogeneous soil deposits. Specifically, we focus on sites whose shear modulus distribution is described by means of a power law that yields zero stiffness at the free surface. First, we show that in some cases (which we characterize in detail) considerations of energy finitude should prevail over considerations of vanishing tractions at the free-surface, as these may pose acuter constrains. We re-evaluate previous contributions in light of this result. Second, we analyze the previously-reported occurrence of \"energy accumulation in upper layers\", providing a physical explanation for it. In passing, we supply estimates of the natural frequencies, and compare these with our previous results.", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2021-02", "volume": "141", "pages": "Art. No. 106530" }, { "id": "authors:fwb3m-c3b43", "collection": "authors", "collection_id": "fwb3m-c3b43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210204-105035105", "type": "article", "title": "A systematic analysis of basin effects on surface ground motion", "author": [ { "family_name": "Ayoubi", "given_name": "Peyman", "orcid": "0000-0001-6795-4923", "clpid": "Ayoubi-Peyman" }, { "family_name": "Mohammadi", "given_name": "Kami", "orcid": "0000-0001-5006-3200", "clpid": "Mohammadi-Kami" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "\"Basin effects\" refers to trapped and reverberating earthquake waves in soft sedimentary deposits overlying convex depressions of the basement bedrock, which significantly alter frequency content, amplitude, and duration of seismic waves. This has played an important role on shaking duration and intensity in past earthquakes such as the M_w 8.0 1985 Michoa'can, Mexico, M_w 6.9 1995 Kobe, Japan, and M_w 7.8 2015 Gorkha, Nepal. Although the phenomenon has been understood and addressed in the literature, it has not been fully incorporated in seismic hazard analysis, and Ground Motion Prediction Equations (GMPE). In this study, we perform an extensive parametric study on the characteristics of surface ground motion associated with basin effects using finite element simulations. We use an elastic medium subjected to vertically propagating SV plane waves and utilize idealized basin shapes to examine the effects of basin geometry and material properties. We specifically study the effects of four dimensionless parameters, the width-to-depth (aspect) ratio, the rock-to-soil material contrast, a dimensionless frequency that quantifies the depth of the basin relative to the dominant incident wavelength, and a dimensionless distance quantifying distance of the basin edges relative to the dominant wavelength. Our results show that basin effects can be reasonably characterized using at least three independent parameters, each of which can significantly alter the resultant ground motion. To demonstrate the application of dimensional analysis applied here, we investigate the response of the Kathmandu Valley during the 2015 M_w 7.8 Gorkha Earthquake in Nepal using an idealized basin geometry and soil properties. Our results show that a simplified model can capture notable characteristics of the ground motion associated with basin effects which suggests that such studies can provide useful insights, relevant to the parameterization of basin effects in GMPEs and design code provisions.", "doi": "10.1016/j.soildyn.2020.106490", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2021-02", "volume": "141", "pages": "Art. No. 106490" }, { "id": "authors:ybe8c-2br08", "collection": "authors", "collection_id": "ybe8c-2br08", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201103-122115068", "type": "article", "title": "Deterministic ground motion simulations with shallow crust nonlinearity at Garner Valley in Southern California", "author": [ { "family_name": "Seylabi", "given_name": "Elnaz", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-Elnaz-E" }, { "family_name": "Restrepo", "given_name": "Doriam", "clpid": "Restrepo-Doriam" }, { "family_name": "Taborda", "given_name": "Ricardo", "clpid": "Taborda-Ricardo" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "We present deterministic ground motion simulations that account for the cyclic multiaxial response of sediments in the shallow crust. We use the Garner Valley in Southern California as a test case. The multiaxial constitutive model is based on the bounding surface plasticity theory in terms of total stress and is implemented in a high\u2010performance computing finite\u2010element parallel code. A major advantage of this model is the small number of free parameters that need to be calibrated given a shear modulus reduction curve and the ultimate soil strength. This, in turn, makes the model suitable for regional\u2010scale simulations, where geotechnical data in the shallow crust are scarce. In this paper, we first describe a series of numerical experiments designed to verify the model implementation. This is followed by a series of idealized large\u2010scale simulations in a 35 x 26 x 4.5 km\u00b3 domain that encompasses the Garner Valley downhole array site, which is an instrumented and well\u2010characterized site in Southern California. Material properties were extracted from the Southern California Earthquake Center Community velocity model, CVM\u2010S4.26, considering its optional geotechnical layer, while the modulus reduction curves and soil strength were selected empirically to constrain the nonlinear soil model parameters. Our nonlinear simulations suggest that peak ground displacements within the valley increase relative to the linear case, while peak ground accelerations can increase or decrease, depending on the frequency content of the excitation. The comparisons of our simulations against hybrid three\u2010dimensional\u2013one\u2010dimensional site response analyses suggest the inadequacy of the latter to capture the complexity of fully three\u2010dimensional simulations.", "doi": "10.1002/eqe.3360", "issn": "0098-8847", "publisher": "Wiley", "publication": "Earthquake Engineering and Structural Dynamics", "publication_date": "2021-01", "series_number": "1", "volume": "50", "issue": "1", "pages": "43-59" }, { "id": "authors:je98a-2c414", "collection": "authors", "collection_id": "je98a-2c414", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210111-160825629", "type": "monograph", "title": "Data-driven Accelerogram Synthesis using Deep Generative Models", "author": [ { "family_name": "Florez", "given_name": "Manuel A.", "clpid": "Florez-Manuel-A" }, { "family_name": "Caporale", "given_name": "Michaelangelo", "clpid": "Caporale-Michaelangelo" }, { "family_name": "Buabthong", "given_name": "Pakpoom", "orcid": "0000-0001-5538-138X", "clpid": "Buabthong-Pakpoom" }, { "family_name": "Ross", "given_name": "Zachary E.", "orcid": "0000-0002-6343-8400", "clpid": "Ross-Z-E" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Meier", "given_name": "Men-Andrin", "orcid": "0000-0002-2949-8602", "clpid": "Meier-Men-Andrin" } ], "abstract": "Robust estimation of ground motions generated by scenario earthquakes is critical for many engineering applications. We leverage recent advances in Generative Adversarial Networks (GANs) to develop a new framework for synthesizing earthquake acceleration time histories. Our approach extends the Wasserstein GAN formulation to allow for the generation of ground-motions conditioned on a set of continuous physical variables. Our model is trained to approximate the intrinsic probability distribution of a massive set of strong-motion recordings from Japan. We show that the trained generator model can synthesize realistic 3-Component accelerograms conditioned on magnitude, distance, and V_(s30). Our model captures the expected statistical features of the acceleration spectra and waveform envelopes. The output seismograms display clear P and S-wave arrivals with the appropriate energy content and relative onset timing. The synthesized Peak Ground Acceleration (PGA) estimates are also consistent with observations. We develop a set of metrics that allow us to assess the training process's stability and tune model hyperparameters. We further show that the trained generator network can interpolate to conditions where no earthquake ground motion recordings exist. Our approach allows the on-demand synthesis of accelerograms for engineering purposes.", "doi": "10.48550/arXiv.2011.09038", "publisher": "arXiv", "publication_date": "2020-11-18" }, { "id": "authors:t0nw9-et471", "collection": "authors", "collection_id": "t0nw9-et471", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201002-151457704", "type": "monograph", "title": "Geotechnical Site Characterization via Deep Neural Networks: Recovering the Shear Wave Velocity Profile of Layered Soils", "author": [ { "family_name": "Ayoubi", "given_name": "Peyman", "orcid": "0000-0001-6795-4923", "clpid": "Ayoubi-P" }, { "family_name": "Seylabi", "given_name": "Elnaz", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-E-E" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "The mechanical property of soils is a vital part of seismic hazard analysis of a site. Such properties are obtained by either in-situ (destructive) experiments such as crosshole or downhole tests, or by non-destructive tests using surface wave inversion methods. While the latter is more favorable due to the cost-efficiency, there are challenges mostly due to computational need, non-uniqueness of inversion results, and fine-tuning parameters. In this article, we use a deep learning framework to circumvent the above-mentioned limitations to output soil mechanical properties, requiring dispersion data as input. Our trained model performs with high accuracy on the test dataset and shows satisfactory performance compared to the ensemble Kalman inversion technique. We finally propose a framework to extend the method to higher dimensions by numerically solving the wave equation in a two-dimensional medium.", "doi": "10.31224/osf.io/jcw3t", "publication_date": "2020-10-02" }, { "id": "authors:qhbyc-v4t41", "collection": "authors", "collection_id": "qhbyc-v4t41", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200218-145423730", "type": "article", "title": "Exact seismic response of smooth rigid retaining walls resting on stiff soil", "author": [ { "family_name": "Garcia-Suarez", "given_name": "Joaquin", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-J" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "The assessment of forces exerted on walls by the backfill is a recurrent problem in geotechnical engineering, owing to its relevance for both retaining systems and underground structures. In particular, the work by Arias and colleagues, and later also the one by Veletsos and Younan, among others, becomes pertinent when considering pressure increments on underground structures triggered by seismic events. As a first step, they studied the response of a rigid retaining wall resting on rigid bedrock subjected to SV waves, introducing some simplifying assumptions. This paper presents the exact solution to this reference problem. The solution is given in horizontal wavenumber domain; hence, it comes in terms of inverse Fourier transforms, which can be approximated numerically in Mathematica , which in turn are verified against finite\u2010element simulations. Specific features of this exact solution that were not captured by prior engineering approximations are highlighted and discussed.", "doi": "10.1002/nag.3082", "issn": "0363-9061", "publisher": "Wiley", "publication": "International Journal for Numerical and Analytical Methods in Geomechanics", "publication_date": "2020-09", "series_number": "13", "volume": "44", "issue": "13", "pages": "1750-1769" }, { "id": "authors:h2he8-3cn12", "collection": "authors", "collection_id": "h2he8-3cn12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200218-142951230", "type": "article", "title": "On the fundamental resonant mode of inhomogeneous soil deposits", "author": [ { "family_name": "Garcia-Suarez", "given_name": "Joaquin", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-J" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "The problem of estimating seismic ground deformation is central to state-of-practice procedures of designing and maintaining infrastructure in earthquake-prone areas. Particularly, the problem of estimating the displacement field in a soft shallow layer overlying rigid bedrock induced by simple shear wave excitation has been favored by engineers due to its simplicity combined with inherent relevance for practical scenarios. We here derive analytical estimates for both the fundamental frequency and the amplitude of the first resonant mode of such systems by applying an intuitive argument based on resonance of single-degree-of-freedom systems. Our estimates do not presuppose a continuous velocity distribution, and can be used for fast assessment of site response in seismic hazard assessment and engineering design. On the basis of the said estimates of fundamental frequency and amplitude, we next propose a novel definition of \"equivalent homogeneous shear modulus\" of the inhomogeneous deposit, and we show that the response of the fundamental mode is controlled primarily by the properties of the layers contiguous to the bedrock. We finally discuss the validity of our argument, and evaluate the accuracy of our results by comparison with analytical and numerical solutions.", "doi": "10.1016/j.soildyn.2020.106190", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2020-08", "volume": "135", "pages": "Art. No. 106190" }, { "id": "authors:j6gxn-kpz82", "collection": "authors", "collection_id": "j6gxn-kpz82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200831-095524760", "type": "article", "title": "SAFER geodatabase for the Kathmandu Valley: Geotechnical and geological variability", "author": [ { "family_name": "El Gilder", "given_name": "Charlotte", "clpid": "El-Gilder-C" }, { "family_name": "Pokhrel", "given_name": "Rama Mohan", "clpid": "Pokhrel-R-M" }, { "family_name": "Vardanega", "given_name": "Paul J.", "clpid": "Vardanega-P-J" }, { "family_name": "De Luca", "given_name": "Flavia", "clpid": "De-Luca-F" }, { "family_name": "De Risi", "given_name": "Raffaele", "clpid": "De-Risi-R" }, { "family_name": "Werner", "given_name": "Maximilian J.", "clpid": "Werner-M-J" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Maskey", "given_name": "Prem Nath", "clpid": "Maskey-P-N" }, { "family_name": "Sextos", "given_name": "Anastasios", "clpid": "Sextos-A" } ], "abstract": "The Kathmandu Valley is within a seismically active region with only few recorded strong-motion data. Geophysical information in the Valley is also sparse. In addition, the absence of an open database which compiles in situ geophysical tests, borehole records, and geotechnical laboratory data is affecting the advancement of knowledge in the region. This article presents SAFER/GEO-591 database, named after the Engineering and Physical Science Research Council (EPSRC)-funded project Seismic Safety and Resilience of Schools in Nepal (SAFER). SAFER/GEO-591 contains data from groundwater wells and boreholes originally commissioned for research and commercial purposes. This work describes (1) the quality assessment and harmonization process conducted on the dataset, (2) the variation of shear-wave velocity (V_S) measurements and geotechnical parameters with depth and elevation in the Valley, (3) the current understanding of the Valley sediment/bedrock topography, and finally (4) new geological cross sections. A companion article presents an updated V_(S30) map across the Valley based on the contributions of this article. The database can be downloaded from the University of Bristol repository via DOI: https://doi.org/10.5523/bris.3gjcvx51lnpuv269xsa1yrb0rw.", "doi": "10.1177/8755293019899952", "issn": "8755-2930", "publisher": "Earthquake Engineering Research Institute", "publication": "Earthquake Spectra", "publication_date": "2020-08", "series_number": "3", "volume": "36", "issue": "3", "pages": "1549-1569" }, { "id": "authors:r52yq-jk734", "collection": "authors", "collection_id": "r52yq-jk734", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200506-121245893", "type": "article", "title": "Site Characterization at Downhole Arrays by Joint Inversion of Dispersion Data and Acceleration Time Series", "author": [ { "family_name": "Seylabi", "given_name": "Elnaz", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-Elnaz-E" }, { "family_name": "Stuart", "given_name": "Andrew M.", "orcid": "0000-0001-9091-7266", "clpid": "Stuart-A-M" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "We present a sequential data assimilation algorithm based on the ensemble Kalman inversion to estimate the near\u2010surface shear\u2010wave velocity profile and damping; this is applicable when heterogeneous data and a priori information that can be represented in forms of (physical) equality and inequality constraints in the inverse problem are available. Although noninvasive methods, such as surface\u2010wave testing, are efficient and cost\u2010effective methods for inferring an V_S profile, one should acknowledge that site characterization using inverse analyses can yield erroneous results associated with the lack of inverse problem uniqueness. One viable solution to alleviate the unsuitability of the inverse problem is to enrich the prior knowledge and/or the data space with complementary observations. In the case of noninvasive methods, the pertinent data are the dispersion curve of surface waves, typically resolved by means of active source methods at high frequencies and passive methods at low frequencies. To improve the inverse problem suitability, horizontal\u2010to\u2010vertical spectral ratio data are commonly used jointly with the dispersion data in the inversion. In this article, we show that the joint inversion of dispersion and strong\u2010motion downhole array data can also reduce the margins of uncertainty in the V_S profile estimation. This is because acceleration time series recorded at downhole arrays include both body and surface waves and therefore can enrich the observational data space in the inverse problem setting. We also show how the proposed algorithm can be modified to systematically incorporate physical constraints that further enhance its suitability. We use both synthetic and real data to examine the performance of the proposed framework in estimation of the V_S profile and damping at the Garner Valley downhole array and compare them against the V_S estimations in previous studies.", "doi": "10.1785/0120190256", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2020-06-01", "series_number": "3", "volume": "110", "issue": "3", "pages": "1323-1337" }, { "id": "authors:7ebnf-8hg54", "collection": "authors", "collection_id": "7ebnf-8hg54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200514-145101649", "type": "article", "title": "Smooth Nonlinear Hysteresis Model for Coupled Biaxial Soil-Pipe Interaction in Sandy Soils", "author": [ { "family_name": "Nguyen", "given_name": "Kien T.", "orcid": "0000-0001-5761-3156", "clpid": "Nguyen-Kien-T" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "Pipelines as infrastructure components are very vulnerable to geohazard-induced ground deformation and failure. Soil\u2013pipe interaction (SPI) thus is very important for the assessment and design of resilient pipeline systems. Previous work on SPI modeling has been based on crude assumptions, such as representation of the soil as uncoupled three-dimensional bilinear springs, and quasi-static loading conditions. This paper proposes a simplified macroelement designed to capture the effects of dynamic SPI in cohesionless soils subjected to arbitrary loading normal to the pipeline axis. First, we present the development of a uniaxial hysteresis model that can capture the smooth nonlinear reaction force-relative displacement curves (FDCs) of SPI problems. Using the unscented Kalman filter, we derived the model parameter \u03ba that controls the smoothness of transition zone from linear to plastic using published empirical and experimental data. We extended this uniaxial model to biaxial loading effects, and showed that the macroelement can capture effects such as pinching and shear\u2013dilation coupling. The model input parameters were calibrated using finite-element (FE) analyses validated by experiments. The FDCs of the biaxial model were verified by comparison with FE and smoothed-particle hydrodynamic (SPH) simulations for different loading patterns: cyclic uniaxial, 0-shaped, 8-shaped, and transient loading. Accounting for smooth nonlinearity, hysteresis, pinching, and coupling effects, the proposed biaxial macroelement showed good agreement with FE and SPH analyses, while maintaining the computational efficiency and simplicity of beam on nonlinear Winkler foundation models, as well as a small number of input parameters.", "doi": "10.1061/(asce)gt.1943-5606.0002230", "issn": "1090-0241", "publisher": "American Society of Civil Engineers", "publication": "Journal of Geotechnical and Geoenvironmental Engineering", "publication_date": "2020-06", "series_number": "6", "volume": "146", "issue": "6", "pages": "Art. No. 04020035" }, { "id": "authors:p4n4z-zds79", "collection": "authors", "collection_id": "p4n4z-zds79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200207-102104947", "type": "article", "title": "Investigating the spatial variability of ground motions during the 2017 Mw 7.1 Puebla-Mexico City earthquake via idealized simulations of basin effects", "author": [ { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Mohammadi", "given_name": "Kami", "orcid": "0000-0001-5006-3200", "clpid": "Mohammadi-K" }, { "family_name": "Ayoubi", "given_name": "Peyman", "orcid": "0000-0001-6795-4923", "clpid": "Ayoubi-P" }, { "family_name": "Mayoral", "given_name": "Juan M.", "clpid": "Mayoral-J-M" }, { "family_name": "Montalva", "given_name": "Gonzalo A.", "clpid": "Montalva-G-A" } ], "abstract": "We use strong motion records of the Mw 7.1 19 September 2017 mainshock and one- and two-dimensional (1D and 2D) simulations at six stations along a linear array across Mexico City, to shed light to the site amplification and ground motion variability observed during the mainshock. The 2017 Puebla-Mexico City earthquake occurred at the edge of the flat slab segment of the subducted Cocos plate beneath central Mexico, rupturing the top half of the plate. Compared to the 1985 subduction zone event, the intraslab Mw 7.1 mainshock was characterized by a much richer high-frequency content. This characteristic transpired into site amplification of the incoming shaking by the sediments of the transition zone, contrary to the 1985 Mw 8.1 Micho\u00e1can earthquake that was amplified by the deeper lake sediments. By means of idealized 1D site and 2D basin models, this paper seeks to disentangle site response from basin resonance and basin edge diffraction effects manifesting in the ground motion records. We specifically compare ground surface observations from the 2017 Mw 7.1 event to 1D and 2D analyses in the time and frequency domain; and empirical transfer functions from several earthquakes to numerical transfer functions computed using 1D and 2D models. Comparison of empirical and simulated amplification spectra shows that, although our 2D model does not capture all the peaks and troughs of the frequency response, theory and observations are nonetheless in good agreement across the entire frequency spectrum. And while frequency peaks of the 1D and 2D models are aligned in the range f > 0.2 Hz, the long period (f < 0.01 Hz) match between simulations and observations demonstrates that the 2D model appropriately captures the effects of the largest characteristic lengths of the basin, namely the basin width. In the intermediate frequency range (0.01 Hz < f < 0.2 Hz), our 2D model captures the scattering of the energy by the concave shape of the basin-rock interface via spectral deamplification, albeit not as strongly as is evidenced by the observations. One-dimensional site response on the other hand cannot capture the larger scale features below 0.2 Hz, which were likely relevant to the performance of lifelines and other infrastructure networks.", "doi": "10.1016/j.soildyn.2020.106073", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2020-05", "volume": "132", "pages": "Art. no. 106073" }, { "id": "authors:93zwy-z6k13", "collection": "authors", "collection_id": "93zwy-z6k13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200220-090311459", "type": "monograph", "title": "Geometrical Optics applied to 1D Site Response of Inhomogeneous Soil Deposits", "author": [ { "family_name": "Garcia-Suarez", "given_name": "Joaquin", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-J" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Seylabi", "given_name": "Elnaz E.", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-E-E" } ], "abstract": "The technique referred as Geometrical Optics entails considering the wave propagation in a heterogeneous medium as if it happened with infinitely small wavelength. This classic simplification allows to obtain useful approximate analytical results in cases where complete description of the waveform behavior is virtually unattainable, hence its wide use in Physics. This approximation is also commonly termed Ray Theory, and it has already been thoroughly applied in Seismology. This text presents an application of Geometrical Optics to 1D Site Response (1DSR): it is used herein to, first, explain and elucidate the generality of some previous observations and results; second, to partially settle an open question in 1DSR, namely \"what are the equivalent homogeneous properties that yield the same response, in terms of natural frequencies and resonance amplitude, for a certain inhomogeneous site?\", provided few assumptions.", "doi": "10.31224/osf.io/db7jv", "publication_date": "2020-02-18" }, { "id": "authors:v9te7-1fr64", "collection": "authors", "collection_id": "v9te7-1fr64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200220-144007826", "type": "monograph", "title": "Dimensional Analysis: Overview and applications to problems of Soil-Structure Interaction", "author": [ { "family_name": "Kusanovic", "given_name": "Danilo S.", "orcid": "0000-0002-0935-2577", "clpid": "Kusanovic-D-S" }, { "family_name": "Garcia-Suarez", "given_name": "Joaquin", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-J" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "Dimensional Analysis is a long-established tool widely used in many branches of engineering and science. However, applications in geotechnical engineering, and in particular soil-structure interaction (SSI), have barely been explored, in spite of the method's potential to clarify parameter influence and shed light on the range of response regimes. The purpose of this text is twofold: (a) it intends to provide a brief introduction to Dimensional Analysis specifically tailored to geotechnical engineers by carefully choosing illustrative examples, (b) it uses Dimensional Analysis to study the parameter space in soil-building interaction problems, emphasizing modeling choices and using a finite-element model to demonstrate the concept of physical similarity. The suitability of using certain dimensionless parameters over others is discussed based on and their magnitude and sensitivity analysis.", "doi": "10.31224/osf.io/m3ycp", "publication_date": "2019-11-09" }, { "id": "authors:q7nsj-kye50", "collection": "authors", "collection_id": "q7nsj-kye50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190329-083647876", "type": "article", "title": "Site effects in Mexico City basin: Past and present", "author": [ { "family_name": "Mayoral", "given_name": "J. M.", "clpid": "Mayoral-J-M" }, { "family_name": "Asimaki", "given_name": "D.", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Tepalcapa", "given_name": "S.", "clpid": "Tepalcapa-S" }, { "family_name": "Wood", "given_name": "C.", "clpid": "Wood-C" }, { "family_name": "Roman-de la Sancha", "given_name": "A.", "clpid": "Roman-de-la-Sancha-A" }, { "family_name": "Hutchinson", "given_name": "T.", "clpid": "Hutchinson-Tara" }, { "family_name": "Franke", "given_name": "K.", "clpid": "Franke-K" }, { "family_name": "Montalva", "given_name": "G.", "clpid": "Montalva-G" } ], "abstract": "Due to the unique subsoil conditions prevailing in the Mexico City basin, seismic risk has been strongly correlated to site effects. Thus, during the Mw 8.1 09/19/1985 subduction fault earthquake, and its strong aftershock Mw 7.5 09/21/1985, extensive damage was observed in the area, along with the loss of thousands of lives, despite these events had an epicentral distance of around 430\u202fkm from Mexico City. The observed damage was mostly due to site affects originated by the high plastiCity clay deposits found in the basin, which lead to large amplifications, and duration elongation of the ground motions coming from the epicenter. In addition, a frequency content modification occurs, which in turn, leads to a double resonance effect between the incoming ground motions, soil deposits, and the damaged buildings. Exactly 32 years after this devastating event, the Mw 7.1 09/19/2017 normal fault earthquake, reminded us of the importance of accounting for site effects, and most importantly the need to carry out a proper characterization of basin geometry, soil profile configuration, hydraulic conditions, and maintenance-structure periodic assessments of the building stock in Mexico City. This is required to reduce uncertainties of seismic vulnerability studies for extreme-event seismic hazard scenarios. In this paper, the role of site response and seismic soil-structure interaction as key factors responsible of the observed damage in the City is revisited, through series of 3D finite difference models of typical structure-foundation-soil typologies found at the areas where most of the damage was observed, highlighting its clear impact in the final damage distribution observed around the City.", "doi": "10.1016/j.soildyn.2019.02.028", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2019-06", "volume": "121", "pages": "369-382" }, { "id": "authors:hw56b-7dr23", "collection": "authors", "collection_id": "hw56b-7dr23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181115-142914482", "type": "article", "title": "How topography-dependent are topographic effects? Complementary numerical modeling of centrifuge experiments", "author": [ { "family_name": "Jeong", "given_name": "Seokho", "clpid": "Jeong-Seokho" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Dafni", "given_name": "Jacob", "clpid": "Dafni-J" }, { "family_name": "Wartman", "given_name": "Joseph", "clpid": "Wartman-J" } ], "abstract": "Topographic effects, the modification of seismic shaking by irregular topographies compared to flat ground, have been extensively studied. Very few studies, however, have investigated the effects of the stratigraphy and nonlinear response of the underlying geology on topographic amplification. Furthermore, most experimental studies have been performed in the field, where it is often difficult to establish an ideal flat-ground reference station, as well as to characterize the soil properties and their spatial variability in sufficient detail. Dafni [1] recently tested the seismic response of step-like slopes in a series of centrifuge experiments, where the incident motion, reference station and material properties were characterized in detail. In this study, we investigated the influence of the container boundary on topographic effects observed in the centrifuge experiments by performing numerical simulations with and without the container boundary. Our analysis suggested that the rigid-body rocking motion of the centrifuge container likely increased the experimental topographic spectral ratios, contributing to the discrepancy between the simulated and observed spectral ratios. We also found that although the laminar box lateral boundaries caused spurious reflections, they didn't qualitatively affect the ground surface amplification pattern compared to numerical predictions of the same configuration without boundaries. At the same time, and most importantly, however, we found that the baseplate \u2013by trapping waves scattered and diffracted by the slope\u2013 amplified the ground motion at the crest up to one order of magnitude compared to numerical predictions of the response in absence of the baseplate. Our results show that topographic effects can be significantly affected by the underlying soil stratigraphy, and allude to the potentially significant role of this phenomenon in elevating seismic risk in regions with strong topographic relief. The findings of this study also suggest that future studies will benefit from clear understanding and careful considerations of capabilities and limitations of different investigation methods and that the numerical modeling and the lab testing (or the field testing) methods should complement each other.", "doi": "10.1016/j.soildyn.2018.10.028", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2019-01", "volume": "116", "pages": "654-667" }, { "id": "authors:fh80m-0gx64", "collection": "authors", "collection_id": "fh80m-0gx64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180807-130938280", "type": "article", "title": "On the complexity of seismic waves trapped in irregular topographies", "author": [ { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Mohammadi", "given_name": "Kami", "orcid": "0000-0001-5006-3200", "clpid": "Mohammadi-K" } ], "abstract": "Documented observations from strong seismic events have repeatedly shown that the ground surface topography significantly affects the characteristics of seismic waves (amplitude, frequency and duration) travelling from the deeper layers of the crust compared to what the ground motion would have been on the surface of a flat homogeneous linear elastic half-space. Although numerous theoretical studies have qualitatively corroborated these observations, they systematically underestimate the absolute level of topographic amplification up to an order of magnitude or more in some cases. In this paper, we try to bridge the quantitative gap between previous theoretical studies and observations by systematically studying the role of geometry, stratigraphy, and ground motion characteristics through a series of elaborate numerical analyses. We show a collection of examples that highlight the effects of topography on seismic ground shaking, and we point out what these results suggest in the context of the current state of earthquake engineering practice. Examples range from semi-analytical solutions of wave propagation in infinite wedges to three-dimensional numerical simulations of topography effects using digital elevation map-generated models and layered geologic features. We conclude by demonstrating that topography effects vary strongly with the stratigraphy and material properties of the underlying geologic materials, and thus it cannot be accurately predicted by studying the effects of ground surface geometry alone.", "doi": "10.1016/j.soildyn.2018.07.020", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2018-11", "volume": "114", "pages": "424-437" }, { "id": "authors:bq5fa-jrb21", "collection": "authors", "collection_id": "bq5fa-jrb21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180814-143441650", "type": "book_section", "title": "On the complexity of seismic waves trapped in non-flat geologic features", "author": [ { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Mohammadi", "given_name": "Kami", "orcid": "0000-0001-5006-3200", "clpid": "Mohammadi-K" } ], "abstract": "Most earthquake engineering and seismological models make the sweeping assumption that the world is flat. The\nground surface topography, however, has been repeatedly shown to strongly affect the amplitude, frequency, duration\nand damage induced by earthquake shaking, effects mostly ignored in earthquake simulations and engineering design.\nIn this talk, I will show a collection of examples that highlight the effects of topography on seismic ground shaking, and I\nwill point out what these results suggest in the context of the current state-of-earthquake engineering practice. Examples\nwill range from semi-analytical solutions of wave propagation in infinite wedge to three-dimensional numerical\nsimulations of topography effects using digital elevation map-generated models and layered geologic features. I will\nconclude by demonstrating that 'topography' effects vary strongly with the stratigraphy and inelastic behavior of the\nunderlying geologic materials, and thus cannot be accurately predicted by studying the effects of ground surface\ngeometry alone.", "publisher": "Caltech Library", "publication_date": "2018-08-15" }, { "id": "authors:as8rk-jjb29", "collection": "authors", "collection_id": "as8rk-jjb29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180523-153705346", "type": "article", "title": "A Generic Velocity Profile for Basin Sediments in California Conditioned on V_(S30)", "author": [ { "family_name": "Shi", "given_name": "Jian", "clpid": "Shi-Jian-CIVILENG" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "The near\u2010surface soil layers of sedimentary basins play a critical role in modifying the amplitude, frequency, and duration of earthquake ground shaking and, thus, are an important factor to consider in ground\u2010motion simulations, the development of site amplification factors, and earthquake hazard evaluations on a regional scale. In this article, we present a sediment velocity model (SVM) that translates V_(S30) and a proxy that describes the stiffness of the near\u2010surface sediments into a 1D velocity profile suitable for use in wave\u2010propagation\u2010based ground\u2010motion predictions. We develop the SVM based on the statistics of 914 measured velocity profiles. We conduct a validation study and show that the SVM can satisfactorily predict both 1D shear\u2010wave velocity profiles and linear site amplification factors. Lastly, we propose two correlations that enable the stochastic realization of the SVM profiles.", "doi": "10.1785/0220170268", "issn": "0895-0695", "publisher": "Seismological Society of America", "publication": "Seismological Research Letters", "publication_date": "2018-07", "series_number": "4", "volume": "89", "issue": "4", "pages": "1397-1409" }, { "id": "authors:51j2y-0zg93", "collection": "authors", "collection_id": "51j2y-0zg93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-152700336", "type": "book_section", "title": "On the Applicability of Shear Strain Index as a Proxy for Site Response Nonlinearity", "book_title": "Geotechnical Earthquake Engineering and Soil Dynamics V: Seismic Hazard Analysis, Earthquake Ground Motions, and Regional-Scale Assessment", "author": [ { "family_name": "Shi", "given_name": "Jian", "clpid": "Shi-Jian-CIVILENG" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "contributor": [ { "family_name": "Brandenberg", "given_name": "Scott J.", "clpid": "Brandenberg-S-J" }, { "family_name": "Manzari", "given_name": "Majid T.", "clpid": "Manzari-M-T" } ], "abstract": "Several recent studies have emphasized the advantages of conducting fully nonlinear site response analyses over the more conventional equivalent linear method, especially for strong ground motion and high frequency response predictions. Since the maximum soil shear strain (\u03b3_(max)) reflects the degree of nonlinearity of the soil, recent studies have introduced the concept of a threshold \u03b3_(max) to determine the conditions under which nonlinear analyses are necessary to provide credible site response predictions. However, as \u03b3_(max) cannot be calculated a priori (i.e., before conducting any site response analysis), a proxy defined as the ratio of peak velocity of the input motion (PGV) to the time-averaged shear-wave velocity in the top 30 meters (V_(S30)), i.e., PGV/V_(S30), has been proposed instead. In this study, we quantify the appropriateness of PGV/V_(S30) (also referred to as shear strain index, I\u03b3) as a proxy for \u03b3_(max), using a statistically significant number of ground motions and sites and using nonlinear site response simulations. We find that I_\u03b3 is a reliable proxy for \u03b3_(max) only for sites with no sharp shear-wave velocity (V_S) impedance contrasts; otherwise it can underestimate \u03b3_(max) by an order of magnitude or more. We lastly propose a correction factor called heterogeneity factor (HF), which is dependent on the velocity contrast of the V_S profile, and when applied upon I_\u03b3, improves the mean and reduces the standard deviation of the I_\u03b3 \u2013 \u03b3_(max) correlation.", "doi": "10.1061/9780784481462.053", "isbn": "9780784481462", "publisher": "American Society of Civil Engineers", "place_of_publication": "Reston, VA", "publication_date": "2018-06-07", "pages": "550-558" }, { "id": "authors:tvhd6-vzv65", "collection": "authors", "collection_id": "tvhd6-vzv65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-154056286", "type": "book_section", "title": "Bayesian Estimation of Nonlinear Soil Model Parameters Using Centrifuge Experimental Data", "book_title": "Geotechnical Earthquake Engineering and Soil Dynamics V: Slope Stability and Landslides, Laboratory Testing, and In Situ Testing", "author": [ { "family_name": "Seylabi", "given_name": "Elnaz Esmaeilzadeh", "orcid": "0000-0003-0718-372X", "clpid": "Seylabi-E-E" }, { "family_name": "Ebrahimian", "given_name": "Hamed", "orcid": "0000-0003-1992-6033", "clpid": "Ebrahimian-Hamed" }, { "family_name": "Zhang", "given_name": "Wenyang", "clpid": "Zhang-Wenyang" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Taciroglu", "given_name": "Ertugrul", "clpid": "Taciroglu-E" } ], "contributor": [ { "family_name": "Brandenberg", "given_name": "Scott J.", "clpid": "Brandenberg-S-J" }, { "family_name": "Manzari", "given_name": "Majid T.", "clpid": "Manzari-M-T" } ], "abstract": "Calibration of nonlinear soil models from experimental data is an essential capability in research and engineering practice alike; however, this task is typically conducted by trial and error. In this study, we describe a Bayesian filtering technique, which is based on an unscented Kalman filter, to systematically assimilate data and estimate the parameters of a veritable soil plasticity model. We first verify the framework using a numerical example. Then, we use the technique to estimate the statistics of the parameters for a multiaxial plasticity model using data from a series of centrifuge tests and infer the maximum shear modulus G_(max), small strain damping, and shear modulus reduction curve G/G_(max). We show that the calibrated soil model, which has a vanished elastic range and a bounding surface, is successful in predicting the soil response for the range of input excitations used in the centrifuge tests. The technique is applicable to other soil models and can be implemented and utilized easily, provided that a standard interface to the soil material model is available.", "doi": "10.1061/9780784481486.042", "isbn": "9780784481486", "publisher": "American Society of Civil Engineers", "place_of_publication": "Reston, VA", "publication_date": "2018-06-07", "pages": "404-413" }, { "id": "authors:9nsgy-x8g07", "collection": "authors", "collection_id": "9nsgy-x8g07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-151131068", "type": "book_section", "title": "A Quasi-Static Displacement-Based Approximation of Seismic Earth Pressures on Rigid Walls", "book_title": "Geotechnical Earthquake Engineering and Soil Dynamics V: Numerical Modeling and Soil Structure Interaction", "author": [ { "family_name": "Garcia-Suarez", "given_name": "Joaquin", "orcid": "0000-0001-8830-4348", "clpid": "Garcia-Suarez-J" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "contributor": [ { "family_name": "Brandenberg", "given_name": "Scott J.", "clpid": "Brandenberg-S-J" }, { "family_name": "Manzari", "given_name": "Majid T.", "clpid": "Manzari-M-T" } ], "abstract": "A number of linear-elastic solutions have been dedicated to resolve the problem of earth pressures on a rigid wall overlying rigid bedrock, among which, the classic solutions have been provided by Matsuo and Ohara (1960), Wood (1973), and Veletsos and Younan (1994). Wood's solution is mathematically involved (it requires evaluation of a double infinite sum) and the other two involve severe simplifying assumptions. An approximation procedure is presented to develop easy-to-evaluate estimates for the lateral earth thrust on rigid retaining walls under quasi-static loading. The procedure is based on the estimation of soil kinematic variables in the vicinity of the wall, from which strains, stresses, and total thrust are obtained. While the procedure is presented for quasi-static loading of a rigid wall overlaying rigid bedrock, this novel approach could be used to account for other complex effects that have been cumbersome to include in state-of-the art earth pressures procedures, such as dynamic loading, soil non-linear behavior, and wall compliance.", "doi": "10.1061/9780784481479.031", "isbn": "9780784481479", "publisher": "American Society of Civil Engineers", "place_of_publication": "Reston, VA", "publication_date": "2018-06-07", "pages": "300-311" }, { "id": "authors:97wkp-q1v14", "collection": "authors", "collection_id": "97wkp-q1v14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180629-082818097", "type": "book_section", "title": "Basin Effects in Strong Ground Motion: A Case Study from the 2015 Gorkha, Nepal, Earthquake", "book_title": "Geotechnical Earthquake Engineering and Soil Dynamics V: Seismic Hazard Analysis, Earthquake Ground Motions, and Regional-Scale Assessment", "author": [ { "family_name": "Ayoubi", "given_name": "Peyman", "orcid": "0000-0001-6795-4923", "clpid": "Ayoubi-P" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Mohammadi", "given_name": "Kami", "orcid": "0000-0001-5006-3200", "clpid": "Mohammadi-K" } ], "contributor": [ { "family_name": "Brandenberg", "given_name": "Scott J.", "clpid": "Brandenberg-S-J" }, { "family_name": "Manzari", "given_name": "Majid T.", "clpid": "Manzari-M-T" } ], "abstract": "The term \"basin effects\" refers to entrapment and reverberation of earthquake waves in soft sedimentary deposits underlain by concave basement rock structures. Basin effects can significantly affect the amplitude, frequency, and duration of strong ground motion, while the cone-like geometry of the basin edges gives rise to large amplitude surface waves through seismic wave diffraction and energy focusing, a well-known characteristic of basin effects. In this research, we study the role of basin effects in the mainshock ground motion data recorded at the Kathmandu Basin, Nepal, during the 2015 M_w7.8 Gorkha earthquake sequence. We specifically try to understand the source of the unusual low frequency reverberating pulse that appeared systematically across the basin, and the unexpected depletion of the ground surface motions from high frequency components, especially away from the basin edges. In order to do that we study the response of a 2D cross section of Kathmandu Basin subjected to vertically propagating plane SV waves. Despite the scarcity of geotechnical information and of strong ground motion recordings, we show that an idealized plane-strain elastic model with a simplified layered velocity structure can capture surprisingly well the low frequency components of the basin ground response. We finally couple the 2D elastic simulation with a 1D nonlinear analysis of the shallow basin sediments. The 1D nonlinear approximation shows improved performance over a larger frequency range relative to the first order approximation of a 2D elastic layered basin response.", "doi": "10.1061/9780784481462.028", "isbn": "9780784481462", "publisher": "American Society of Civil Engineers", "place_of_publication": "New York, NY", "publication_date": "2018-06-07", "pages": "288-296" }, { "id": "authors:zvskz-qed59", "collection": "authors", "collection_id": "zvskz-qed59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-145221319", "type": "book_section", "title": "Investigating the Applicability of Integrated Hydrological Modeling for Mapping Regional Liquefaction Hazard", "book_title": "Geotechnical Earthquake Engineering and Soil Dynamics V: Seismic Hazard Analysis, Earthquake Ground Motions, and Regional-Scale Assessment", "author": [ { "family_name": "Mital", "given_name": "Utkarsh", "clpid": "Mital-U" }, { "family_name": "Rajasekaran", "given_name": "Eswar", "clpid": "Rajasekaran-E" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Das", "given_name": "Narendra N.", "clpid": "Das-N-N" } ], "contributor": [ { "family_name": "Brandenberg", "given_name": "Scott J.", "clpid": "Brandenberg-S-J" }, { "family_name": "Manzari", "given_name": "Majid T.", "clpid": "Manzari-M-T" } ], "abstract": "Soil liquefaction and related phenomena, such as ground deformation and lateral spreading, pose significant risk to distributed and critical infrastructure systems. Although liquefaction vulnerability is controlled by geologic and groundwater conditions, its regional assessment is almost exclusively based on geologic material properties or proxies thereof. In this work, we are developing a multivariate methodology that incorporates groundwater conditions by introducing hydrological variables in regional assessment of liquefaction hazards. More specifically, we use remote sensing data and well-monitoring data to set up an integrated hydrological model that provides estimates of soil moisture and depth to water table. We demonstrate the methodology by presenting a case study from the 2010 El Mayor-Cucapah earthquake in Imperial County. We use reconnaissance data to train a logistic regression model, which yields probabilistic maps of liquefaction occurrence. Preliminary results indicate that the proposed approach may improve the modeling of regional liquefaction assessment at no additional site investigation cost. However, in order to draw quantitative conclusions on the accuracy improvements, more training data is necessary for which we are collaborating with the ARIA Center at JPL-Caltech.", "doi": "10.1061/9780784481462.066", "isbn": "9780784481462", "publisher": "American Society of Civil Engineers", "place_of_publication": "Reston, VA", "publication_date": "2018-06-07", "pages": "677-684" }, { "id": "authors:9r4py-f4b09", "collection": "authors", "collection_id": "9r4py-f4b09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-151717317", "type": "book_section", "title": "A Nonlinear Model Inversion to Estimate Dynamic Soil Stiffness of Building Structures", "book_title": "Geotechnical Earthquake Engineering and Soil Dynamics V: Numerical Modeling and Soil Structure Interaction", "author": [ { "family_name": "Ebrahimian", "given_name": "Hamed", "orcid": "0000-0003-1992-6033", "clpid": "Ebrahimian-Hamed" }, { "family_name": "Ghahari", "given_name": "S. Farid", "clpid": "Ghahari-S-F" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Taciroglu", "given_name": "Ertugrul", "clpid": "Taciroglu-E" } ], "contributor": [ { "family_name": "Brandenberg", "given_name": "Scott J.", "clpid": "Brandenberg-S-J" }, { "family_name": "Manzari", "given_name": "Majid T.", "clpid": "Manzari-M-T" } ], "abstract": "This study presents an output-only model inversion method to jointly estimate the model parameters and foundation input motions in structural models. The model inversion is based on Bayesian finite element model updating using the measured seismic response of the structure. The model parameters to be estimated consist of parameters characterizing the structural model, dynamic soil springs (to account for inertial soil structure interaction effects), and Rayleigh damping. We use the recorded response of the Millikan Library building to the 2002 Yorba Linda earthquake for validation study, in which the recorded structural responses are used to update the structural model resting on soil springs and dashpots. This study is a step forward towards developing model inversion methods that can be used with seismic response of real-world buildings to identify the Rayleigh damping and dynamic soil springs parameters.", "doi": "10.1061/9780784481479.030", "isbn": "9780784481479", "publisher": "American Society of Civil Engineers", "place_of_publication": "Reston, VA", "publication_date": "2018-06-07", "pages": "293-299" }, { "id": "authors:7b8aq-7sh63", "collection": "authors", "collection_id": "7b8aq-7sh63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-150224679", "type": "book_section", "title": "A Modified Uniaxial Bouc-Wen Model for the Simulation of Transverse Lateral Pipe-Cohesionless Soil Interaction", "book_title": "Geotechnical Earthquake Engineering and Soil Dynamics V: Numerical Modeling and Soil Structure Interaction", "author": [ { "family_name": "Nguyen", "given_name": "Kien T.", "clpid": "Nguyen-Kien-T" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "contributor": [ { "family_name": "Brandenberg", "given_name": "Scott J.", "clpid": "Brandenberg-S-J" }, { "family_name": "Manzari", "given_name": "Majid T.", "clpid": "Manzari-M-T" } ], "abstract": "This paper proposes a modified uniaxial Bouc-Wen model to evaluate reaction force-displacement backbone curve for transverse lateral pipe-cohesionless soil interaction. The model is capable of representing the nonlinearity and the smooth transition zone of the curve. Using unscented Kalman filter, the model parameter \u03ba that controls the smoothness of transition zone is derived, on the basis of results from high-fidelity validated finite element analyses. \u03ba is larger in loose sand compared to that in dense sand, implying a smoother transition zone of the curve for loose sand. There is a slight change of \u03ba with pipe burial depth in case of dense sand, while the change is clearer and larger in loose sand. The variation of \u03ba is related to the \"passive-wedge\" and \"plow-through\" failure mode of soil. The model is subsequently implemented in a series of soil-pipe interaction configurations, and the reaction force-deformation curves are found in good agreement with experimental data.", "doi": "10.1061/9780784481479.003", "isbn": "9780784481479", "publisher": "American Society of Civil Engineers", "place_of_publication": "Reston, VA", "publication_date": "2018-06-07", "pages": "25-36" }, { "id": "authors:y53es-fd456", "collection": "authors", "collection_id": "y53es-fd456", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180124-083817416", "type": "article", "title": "PRENOLIN: International Benchmark on 1D Nonlinear Site\u2010Response Analysis\u2014Validation Phase Exercise", "author": [ { "family_name": "R\u00e9gnier", "given_name": "Julie", "clpid": "R\u00e9gnier-J" }, { "family_name": "Asimaki", "given_name": "Dominiki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Shi", "given_name": "Jian", "clpid": "Shi-Jian-CIVILENG" } ], "abstract": "This article presents the main results of the validation phase of the PRENOLIN project. PRENOLIN is an international benchmark on 1D nonlinear (NL) site\u2010response analysis. This project involved 19 teams with 23 different codes tested. It was divided into two phases; with the first phase verifying the numerical solution of these codes on idealized soil profiles using simple signals and real seismic records. The second phase described in this article referred to code validation for the analysis of real instrumented sites.\n\nThis validation phase was performed on two sites (KSRH10 and Sendai) of the Japanese strong\u2010motion networks KiK\u2010net and Port and Airport Research Institute (PARI), respectively, with a pair of accelerometers at surface and depth. Extensive additional site characterizations were performed at both sites involving in situ and laboratory measurements of the soil properties. At each site, sets of input motions were selected to represent different peak ground acceleration (PGA) and frequency content. It was found that the code\u2010to\u2010code variability given by the standard deviation of the computed surface\u2010response spectra is around 0.1 (in log10 scale) regardless of the site and input motions. This indicates a quite large influence of the numerical methods on site\u2010effect assessment and more generally on seismic hazard. Besides, it was observed that site\u2010specific measurements are of primary importance for defining the input data in site\u2010response analysis. The NL parameters obtained from the laboratory measurements should be compared with curves coming from the literature. Finally, the lessons learned from this exercise are synthesized, resulting also in a few recommendations for future benchmarking studies, and the use of 1D NL, total stress site\u2010response analysis.", "doi": "10.1785/0120170210", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2018-04", "series_number": "2", "volume": "108", "issue": "2", "pages": "876-900" }, { "id": "authors:hrc31-rmd74", "collection": "authors", "collection_id": "hrc31-rmd74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180314-105013814", "type": "article", "title": "Parametric estimation of dispersive viscoelastic layered media with application to structural health monitoring", "author": [ { "family_name": "Ebrahimian", "given_name": "Hamed", "orcid": "0000-0003-1992-6033", "clpid": "Ebrahimian-H" }, { "family_name": "Kohler", "given_name": "Monica D.", "orcid": "0000-0002-4703-190X", "clpid": "Kohler-M-D" }, { "family_name": "Massari", "given_name": "Anthony", "orcid": "0000-0002-6561-4674", "clpid": "Massari-A" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "We present a sequential Bayesian estimation method to estimate the material parameters that govern the one-dimensional propagation of shear waves through continuous, layered, viscoelastic solids. While the proposed estimation method is generic, namely, can be applied to waveform inversion problems that satisfy the above conditions, we here employ it for system identification of building structures. We approximate the linear-elastic response of building structures subjected to low-amplitude earthquake base excitations by a multilayer dispersive shear beam model with Kelvin-Voigt material subjected to vertically propagating shear waves. Utilizing the proposed sequential Bayesian estimation method, we sequentially update the probability distribution function of the unknown parameters to reduce the discrepancies between the estimated and measured frequency response functions. We next verify and validate the performance of the proposed estimation method and investigate the limitations of the presented structural system identification approach using two case studies. In the first case study, we use the simulated structural response of a three-dimensional 52-story building model subjected to bi-directional low-amplitude ground shakings. We estimate the frequency-dependent phase velocity and damping ratio, as well as the mass distribution along the building height. Then, we verify the structural damage detection and localization capabilities of the presented system identification approach by comparing the wave model parameters estimated from simulated response of undamaged and damaged structural models. In the second case study, we use data measured from a shake table experiment on a full-scale five-story reinforced concrete building specimen, where the estimated wave model parameters capture the progressive structural damage in the test specimen. The validation studies suggest that the sequential Bayesian estimation method based on viscoelastic dispersive wave propagation can be used for system and damage identification of building structures.", "doi": "10.1016/j.soildyn.2017.10.017", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2018-02", "volume": "105", "pages": "204-223" }, { "id": "authors:v2azp-at081", "collection": "authors", "collection_id": "v2azp-at081", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180809-111909145", "type": "article", "title": "Observations and Simulations of Basin Effects in the Kathmandu Valley During the 2015 Gorkha, Nepal, Earthquake Sequence", "author": [ { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Mohammadi", "given_name": "Kami", "orcid": "0000-0001-5006-3200", "clpid": "Mohammadi-K" }, { "family_name": "Mason", "given_name": "Henry B.", "clpid": "Mason-H-B" }, { "family_name": "Adams", "given_name": "Rachel K.", "clpid": "Adams-R-K" }, { "family_name": "Rajaure", "given_name": "Sudhir", "clpid": "Rajaure-S" }, { "family_name": "Khadka", "given_name": "Diwakar", "clpid": "Khadka-D" } ], "abstract": "The M7.8 Gorkha, Nepal main shock ruptured a segment of the Main Himalayan Thrust (MHT) directly below Kathmandu Valley, causing strong shaking levels across the valley. Strong-motion data reveal an initial 6 s source pulse that was amplified and reverberated within the basin. One of the striking features of the observed ground motions in the valley was the exceptionally low energy of periods less than 2 s, which likely limited the extent and severity of structural damage in Kathmandu compared with alternative rupture scenarios of the same magnitude in the region. Isolated cases of liquefaction and lateral spreading of unconsolidated sediments were also observed, but have not yet revealed a systematic damage pattern. Initial analysis of available data suggests that several different factors, including source and path as well as site effects, were responsible for the unusual ground motions characteristics. In this paper, we provide a short description of the Kathmandu Valley geology and analyze available strong-motion records from the main shock and three strong aftershocks, with the intent to shed light on earthquake reconnaissance observations from this earthquake.", "doi": "10.1193/013117EQS022M", "issn": "8755-2930", "publisher": "Earthquake Engineering Research Institute", "publication": "Earthquake Spectra", "publication_date": "2017-12", "series_number": "S1", "volume": "33", "issue": "S1", "pages": "S35-S53" }, { "id": "authors:2mnfg-fxr20", "collection": "authors", "collection_id": "2mnfg-fxr20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180521-143441555", "type": "book_section", "title": "Parametric Estimation of Wave Dispersion for System Identification of Building Structures", "book_title": "Experimental Vibration Analysis for Civil Structures. EVACES 2017", "author": [ { "family_name": "Ebrahimian", "given_name": "Hamed", "orcid": "0000-0003-1992-6033", "clpid": "Ebrahimian-Hamed" }, { "family_name": "Kohler", "given_name": "Monica D.", "orcid": "0000-0002-4703-190X", "clpid": "Kohler-M-D" }, { "family_name": "Massari", "given_name": "Anthony", "orcid": "0000-0002-6561-4674", "clpid": "Massari-A" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "editor": [ { "family_name": "Conte", "given_name": "Joel P.", "clpid": "Conte-Joel-P" }, { "family_name": "Astroza", "given_name": "Rodrigo", "clpid": "Astroza-Rodrigo" }, { "family_name": "Benzoni", "given_name": "Gianmario", "clpid": "Benzoni-Gianmario" }, { "family_name": "Fletrin", "given_name": "Glauco", "clpid": "Feltrin-Glauco" }, { "family_name": "Loh", "given_name": "Kenneth J.", "clpid": "Loh-Kenneth-J" }, { "family_name": "Moaveni", "given_name": "Babak", "clpid": "Moaveni-Babak" } ], "abstract": "The linear-elastic response of a building structure subjected to an earthquake base excitation can be approximated as the response of a continuous, spatially inhomogenous, dispersive, viscoelastic solid subjected to vertically incident plane shear waves. The frequency-dependent phase velocity and attenuation of seismic energy at different wavelengths, together with the inertial properties of the multilayer solid characterize the response of the building structure. The objective of this study is to identify the structural system by estimating the parameters that characterize the propagation of seismic waves in an equivalent multilayer viscoelastic solid. To pursue this objective, first, the measured dynamic responses of a building structure are used to derive the frequency response functions (FRFs) of the floor absolute acceleration with respect to the base excitation using a seismic interferometry approach. The FRFs obtained from the measured structural responses are then compared with the FRFs estimated using analytical models for one-dimensional shear wave propagation in a multilayer Kelvin-Voigt dispersive medium. Through a recursive Bayesian estimation approach, the parameters characterizing the phase velocity and damping ratio of the multilayer medium are estimated. This study provides a step forward in seismic interferometric identification of building structures by proposing a new method for parametric estimation of shear wave velocity and damping dispersion at the story level of a building structure. The estimated shear wave velocities before and after a damage-inducing event can be used to identify permanent loss of effective lateral stiffness of the building structure at the story level, thus can provide an alternative method for structural health monitoring and damage identification.", "doi": "10.1007/978-3-319-67443-8_70", "isbn": "9783319674438", "publisher": "Springer", "place_of_publication": "Cham, Switzerland", "publication_date": "2017-10-13", "pages": "791-802" }, { "id": "authors:957wp-qf989", "collection": "authors", "collection_id": "957wp-qf989", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170509-141502347", "type": "article", "title": "Characterizing the Kathmandu Valley sediment response through strong motion recordings of the 2015 Gorkha earthquake sequence", "author": [ { "family_name": "Rajaure", "given_name": "S.", "clpid": "Rajaure-S" }, { "family_name": "Asimaki", "given_name": "D.", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Thompson", "given_name": "E. M.", "clpid": "Thompson-E-M" }, { "family_name": "Hough", "given_name": "S.", "orcid": "0000-0002-5980-2986", "clpid": "Hough-S-E" }, { "family_name": "Martin", "given_name": "S.", "clpid": "Martin-S" }, { "family_name": "Ampuero", "given_name": "J. P.", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" }, { "family_name": "Dhital", "given_name": "M. R.", "clpid": "Dhital-M-R" }, { "family_name": "Inbal", "given_name": "A.", "orcid": "0000-0001-8848-7279", "clpid": "Inbal-Asaf" }, { "family_name": "Takai", "given_name": "N.", "clpid": "Takai-N" }, { "family_name": "Shigefuji", "given_name": "M.", "clpid": "Shigefuji-M" }, { "family_name": "Bijukchhen", "given_name": "S.", "clpid": "Bijukchhen-S" }, { "family_name": "Ichiyanagi", "given_name": "M.", "clpid": "Ichiyanagi-M" }, { "family_name": "Sasatani", "given_name": "T.", "clpid": "Sasatani-T" }, { "family_name": "Paudel", "given_name": "L.", "clpid": "Paudel-L" } ], "abstract": "We analyze strong motion records and high-rate GPS measurements of the M 7.8 Gorkha mainshock, M 7.3 Dolakha, and two moderate aftershock events recorded at four stations on the Kathmandu basin sediments, and one on rock-outcrop. Recordings on soil from all four events show systematic amplification relative to the rock site at multiple frequencies in the 0.1\u20132.5 Hz frequency range, and de-amplification of higher frequencies ( >2.5\u201310 Hz). The soil-to-rock amplification ratios for the M 7.8 and M 7.3 events have lower amplitude and frequency peaks relative to the ratios of the two moderate events, effects that could be suggestive of nonlinear site response. Further, comparisons to ground motion prediction equations show that 1) both soil and rock mainshock recordings were severely depleted of high frequencies, and 2) the depletion at high frequencies is not present in the aftershocks. These observations indicate that the high frequency deamplification is additionally related to characteristics of the source that are not captured by simplified ground motion prediction equations, and allude to seismic hazard analysis models being revised \u2013 possibly by treating isolated high frequency radiation sources separately from long period components to capture large magnitude near-source events such as the 2015 Gorkha mainshock.", "doi": "10.1016/j.tecto.2016.09.030", "issn": "0040-1951", "publisher": "Elsevier", "publication": "Tectonophysics", "publication_date": "2017-09-13", "volume": "714-715", "pages": "146-157" }, { "id": "authors:4naa9-fbd36", "collection": "authors", "collection_id": "4naa9-fbd36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170404-150827374", "type": "article", "title": "From Stiffness to Strength: Formulation and Validation of a Hybrid Hyperbolic Nonlinear Soil Model for Site\u2010Response Analyses", "author": [ { "family_name": "Shi", "given_name": "Jian", "clpid": "Shi-Jian-CIVILENG" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "Nonlinear site\u2010response analyses are becoming an increasingly important component of simulated ground motions for engineering applications. For regional\u2010scale problems for which geotechnical data are sparse, the challenge lies in computing site response using a very small number of input parameters. We developed a nonlinear soil model that, using only the shear\u2010wave velocity profile, captures both the low\u2010strain stiffness and large\u2010strain strength of soils and yields reliable predictions of soil response to weak and strong shaking. We here present the formulation of the model and an extensive validation study based on downhole array recordings, with peak ground acceleration (PGA) ranging from 0.01g to 0.9g. We also show that our model, referred to as hybrid hyperbolic (HH), outperforms existing nonlinear formulations and simplified site\u2010response analyses widely used in practice for ground motions that induce more than 0.04% of soil strain (roughly equivalent to PGA higher than 0.05g). In addition to site\u2010specific response predictions at sites with limited site characterization, the HH model can help improve site amplification factors of ground\u2010motion prediction equations (GMPEs) by complementing the empirical data with simulated site\u2010response analyses for very strong ground shaking, as well as physics\u2010based ground\u2010motion simulations, particularly for deeper sedimentary sites with low resonant frequencies.", "doi": "10.1785/0120150287", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2017-06", "series_number": "3", "volume": "107", "issue": "3", "pages": "1336-1355" }, { "id": "authors:x64jj-6va61", "collection": "authors", "collection_id": "x64jj-6va61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170817-140923317", "type": "book_section", "title": "Topography Effects Are Not Dominated by Ground Surface Geometry: A Site Effects Paradox", "book_title": "Geotechnical Frontiers 2017: Seismic Performance and Liquefaction", "author": [ { "family_name": "Mohammadi", "given_name": "K.", "orcid": "0000-0001-5006-3200", "clpid": "Mohammadi-K" }, { "family_name": "Asimaki", "given_name": "D.", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "contributor": [ { "family_name": "Brandon", "given_name": "Thomas L.", "clpid": "Brandon-T-L" }, { "family_name": "Valentine", "given_name": "Richard J.", "clpid": "Valentine-R-J" } ], "abstract": "The material properties and the geometry of near surface soil layers, known as local site conditions, can significantly change the input seismic motion compared to the simple case of homogeneous linear elastic half-space. Our recent studies have shown that the effects of topography coupled to site response can lead to ground motion aggravation larger than the superposition of site and geometry amplification. These soil-topography coupling effects arise from seismic waves trapped in the near surface soil layers, are amplified or deamplified as a consequence of stiffness contrast, and are further modified due to scattering caused by irregular interface and ground surface. In this study, we investigate the coupling effects for 2D idealized convex features through a systematic analysis. The resulting trends, which are presented in the form of dimensionless amplification factors, clearly demonstrate the nonlinear nature of coupling effects, which cannot be predicted by modifying simulations of topography effects on rock by 1D site amplification factors, a posteriori. We then quantify these coupling effects through 3D site-specific analyses at selected strong ground motion stations in California, which yield more realistic amplification patterns (using 1 arc-second DEM extracted surface topographies and measured Vs profile). The results of coupling effects provide a basis as to how it can be incorporated in the proposed design motion of seismic code provisions.", "doi": "10.1061/9780784480489.018", "isbn": "978-0-7844-8048-9", "publisher": "American Society of Civil Engineers", "place_of_publication": "Reston, VA", "publication_date": "2017-03", "pages": "171-181" }, { "id": "authors:xg2kp-0d342", "collection": "authors", "collection_id": "xg2kp-0d342", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161109-082112057", "type": "article", "title": "Topographic proxies from 2-D numerical analyses", "author": [ { "family_name": "Rai", "given_name": "Manisha", "clpid": "Rai-M" }, { "family_name": "Rodriguez-Marek", "given_name": "Adrian", "clpid": "Rodriguez-Marek-A" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "We use 2D numerical analyses at ground motion stations from the NGA-West2 dataset to develop parameters to predict the effect of surface topography on response spectra. The simplistic numerical analyses use sinusoidal input motions, uniform soil profiles, elastic soil properties, and absorbing boundary conditions. We define several topographic parameters for stations using the natural logarithm of 2D amplifications in peak ground acceleration of a sinusoidal input motion in different orientations. The natural log of 2D amplifications when averaged over multiple orientations is found to have the most predictive power among the studied parameters. We also explore the relationship between the topographic parameters developed in this study, and the topographic parameters developed at the same sites in an earlier study (Rai et al. in Earthq Spectra, 2016b).", "doi": "10.1007/s10518-016-9933-4", "issn": "1570-761X", "publisher": "Springer", "publication": "Bulletin of Earthquake Engineering", "publication_date": "2016-11", "series_number": "11", "volume": "14", "issue": "11", "pages": "2959-2975" }, { "id": "authors:akdpx-7bt49", "collection": "authors", "collection_id": "akdpx-7bt49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161222-090304683", "type": "article", "title": "International Benchmark on Numerical Simulations for 1D, Nonlinear Site Response (PRENOLIN): Verification Phase Based on Canonical Cases", "author": [ { "family_name": "R\u00e9gnier", "given_name": "Julie", "clpid": "R\u00e9gnier-Julie" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Shi", "given_name": "Jian", "clpid": "Shi-Jian-CIVILENG" } ], "abstract": "PREdiction of NOn\u2010LINear soil behavior (PRENOLIN) is an international benchmark aiming to test multiple numerical simulation codes that are capable of predicting nonlinear seismic site response with various constitutive models. One of the objectives of this project is the assessment of the uncertainties associated with nonlinear simulation of 1D site effects. A first verification phase (i.e., comparison between numerical codes on simple idealistic cases) will be followed by a validation phase, comparing the predictions of such numerical estimations with actual strong\u2010motion recordings obtained at well\u2010known sites. The benchmark presently involves 21 teams and 23 different computational codes.\nWe present here the main results of the verification phase dealing with simple cases. Three different idealized soil profiles were tested over a wide range of shear strains with different input motions and different boundary conditions at the sediment/bedrock interface. A first iteration focusing on the elastic and viscoelastic cases was proved to be useful to ensure a common understanding and to identify numerical issues before pursuing the nonlinear modeling. Besides minor mistakes in the implementation of input parameters and output units, the initial discrepancies between the numerical results can be attributed to (1) different understanding of the expression \"input motion\" in different communities, and (2) different implementations of material damping and possible numerical energy dissipation. The second round of computations thus allowed a convergence of all teams to the Haskell\u2013Thomson analytical solution in elastic and viscoelastic cases. For nonlinear computations, we investigate the epistemic uncertainties related only to wave propagation modeling using different nonlinear constitutive models. Such epistemic uncertainties are shown to increase with the strain level and to reach values around 0.2 (log_(10) scale) for a peak ground acceleration of 5\u2009\u2009m/s^2 at the base of the soil column, which may be reduced by almost 50% when the various constitutive models used the same shear strength and damping implementation.", "doi": "10.1785/0120150284", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2016-10", "series_number": "5", "volume": "106", "issue": "5", "pages": "2112-2135" }, { "id": "authors:3kp16-ce898", "collection": "authors", "collection_id": "3kp16-ce898", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151204-092729660", "type": "article", "title": "Geotechnical Effects of the 2015 Magnitude 7.8 Gorkha, Nepal, Earthquake and Aftershocks", "author": [ { "family_name": "Moss", "given_name": "Robb E. S.", "clpid": "Moss-R-E-S" }, { "family_name": "Thompson", "given_name": "Eric M.", "clpid": "Thompson-E-M" }, { "family_name": "Kieffer", "given_name": "D. Scott", "clpid": "Kieffer-D-S" }, { "family_name": "Tiwari", "given_name": "Binod", "clpid": "Tiwari-B" }, { "family_name": "Hashash", "given_name": "Youssef M. A.", "clpid": "Hashash-Y-M-A" }, { "family_name": "Acharya", "given_name": "Indra", "clpid": "Acharya-I" }, { "family_name": "Adhikari", "given_name": "Basanta Raj", "clpid": "Adhikari-B-R" }, { "family_name": "Asimaki", "given_name": "Domniki", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Clahan", "given_name": "Kevin B.", "clpid": "Clahan-K-B" }, { "family_name": "Collins", "given_name": "Brian D.", "clpid": "Collins-B-D" }, { "family_name": "Dahal", "given_name": "Sachindra", "clpid": "Dahal-S" }, { "family_name": "Jibson", "given_name": "Randall W.", "clpid": "Jibson-R-W" }, { "family_name": "Khadka", "given_name": "Diwakar", "clpid": "Khadka-D" }, { "family_name": "Macdonald", "given_name": "Amy", "clpid": "Macdonald-A" }, { "family_name": "Madugo", "given_name": "Chris L. M.", "clpid": "Madugo-C-L-M" }, { "family_name": "Mason", "given_name": "H. Benjamin", "clpid": "Mason-H-B" }, { "family_name": "Pehlivan", "given_name": "Menzer", "clpid": "Pehlivan-M" }, { "family_name": "Rayamajhi", "given_name": "Deepak", "clpid": "Rayamajhi-D" }, { "family_name": "Uprety", "given_name": "Sital", "clpid": "Uprety-S" } ], "abstract": "This article summarizes the geotechnical effects of the 25 April 2015 M 7.8 Gorkha, Nepal, earthquake and aftershocks, as documented by a reconnaissance team that undertook a broad engineering and scientific assessment of the damage and collected perishable data for future analysis. Brief descriptions are provided of ground shaking, surface fault rupture, landsliding, soil failure, and infrastructure performance. The goal of this reconnaissance effort, led by Geotechnical Extreme Events Reconnaissance, is to learn from earthquakes and mitigate hazards in future earthquakes.", "doi": "10.1785/0220150158", "issn": "0895-0695", "publisher": "Seismological Society of America", "publication": "Seismological Research Letters", "publication_date": "2015-11", "series_number": "6", "volume": "86", "issue": "6", "pages": "1514-1523" }, { "id": "authors:9ns79-5n074", "collection": "authors", "collection_id": "9ns79-5n074", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150212-100529768", "type": "article", "title": "Bias assessment in Incremental Dynamic Analysis due to record scaling", "author": [ { "family_name": "Zacharenaki", "given_name": "Athanasia", "clpid": "Zacharenaki-A" }, { "family_name": "Fragiadakis", "given_name": "Michalis", "clpid": "Fragiadakis-M" }, { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Papadrakakis", "given_name": "Manolis", "clpid": "Papadrakakis-M" } ], "abstract": "Incremental Dynamic Analysis (IDA) involves a series of nonlinear response history analyses with a suite of incrementally scaled ground motion records. Although IDA is perhaps the most comprehensive seismic performance assessment method, it receives criticism because several ground motion records are scaled up until the structure collapses. The scaling practice often results to unrealistic multipliers, thus modifying the amplitude of the ground motion and introducing bias on the structural performance estimation. Record scaling is a common practice in earthquake engineering due to the lack of natural records corresponding to large magnitudes and/or small distances from the fault rupture location. In this work we use a large number of ground motion records to compare the predictions of IDA with that of unscaled ground motions and we propose a new methodology in order to quantify the bias introduced in IDA. Apart from natural records, we have conducted broadband ground motion simulations for rupture scenarios of weak, medium and large magnitude events in order to expand our record database. The investigation is performed on a series of inelastic single-degree-of-freedom systems and on two multistory steel moment frame buildings. The results pinpoint both qualitatively and quantitatively, for the full range of limit-states, the bias that IDA introduces on the structural performance estimation.", "doi": "10.1016/j.soildyn.2014.09.007", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2014-12", "volume": "67", "pages": "158-168" }, { "id": "authors:b78xk-gxf40", "collection": "authors", "collection_id": "b78xk-gxf40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140902-134021129", "type": "article", "title": "Ground-Motion Observations at Hotel Montana during the M 7.0 2010 Haiti Earthquake: Topography or Soil Amplification?", "author": [ { "family_name": "Assimaki", "given_name": "D.", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Jeong", "given_name": "S.", "clpid": "Jeong-S" } ], "abstract": "Unusually severe structural damage was reported during the 2010 M 7.0 Haiti earthquake in the vicinity of Hotel Montana, located on top of a ridge in the district of P\u00e9tionville. Prompted by the observations, U.S. Geological Survey seismic stations were deployed, and aftershock recordings indicated ground\u2010motion amplification on the top of the hill compared to adjacent stations on reference site conditions. The presence of topographic relief has been shown to significantly aggravate the consequences of strong ground motion during past events, and topographic effects were brought forward to explain the observations. In this paper, we test the hypothesis of topographic amplification as the dominant factor that contributed to the damage concentration in the vicinity of Hotel Montana. We initially conduct numerical simulations of the ridge seismic response assuming elastic homogeneous site conditions, and show that numerical predictions of topographic amplification disagree with the field data both in amplitude and in frequency. Conversely, while 1D ground\u2010response analyses for the site conditions at the hilltop predict amplification in the same frequency range as the field data, they significantly underestimate the recorded amplitude. We then conduct numerical simulations of the foothill ridge response to seismic motion while accounting for soil layering, and qualitatively demonstrate that the recorded amplification is most likely attributed to coupled site\u2013topographic amplification effects, namely to seismic waves trapped in the soft soil layers of the near surface, amplified as a consequence of reverberations, and further modified due to diffraction and scattering upon incidence on the irregular ground surface. Parametric investigations of the topography\u2013soil amplification coupling effects are then conducted, and our results show that when accounting for a hypothetical soil\u2013bedrock interface at 100 m depth, predictions are in excellent agreement with the observed motion.", "doi": "10.1785/0120120242", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2013-10", "series_number": "5", "volume": "103", "issue": "5", "pages": "2577-2590" }, { "id": "authors:ntym1-w7158", "collection": "authors", "collection_id": "ntym1-w7158", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140904-162809518", "type": "article", "title": "Site Effects in Structural Response Predictions of Inelastic SDOF Oscillators", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Li", "given_name": "Wei", "orcid": "0000-0003-2543-2558", "clpid": "Li-Wei" }, { "family_name": "Fragiadakis", "given_name": "Michalis", "clpid": "Fragiadakis-M" } ], "abstract": "We study how the inelastic structural response predicted via synthetic seismograms is affected by the selection of site response models in ground motion simulations. We first generate synthetics for multiple scenarios and site conditions in Southern California using attenuation relations, site specific linear, viscoelastic and nonlinear analyses, and estimate the ground motion variability that results from the soil model selection. We next use bilinear single degree-of-freedom oscillators to demonstrate how this variability propagates to the inelastic structural response predictions. Results show high bias and scatter of the inelastic displacement ratio predicted using the empirical and linear elastic site response models relative to the nonlinear, for periods close to the fundamental period of the site. For the synthetic motions and sites used, we derive empirical correlations between the amount of bias and period range where it manifests, and selected input motion and site parameters.", "doi": "10.1193/1.4000056", "issn": "8755-2930", "publisher": "Earthquake Engineering Research Institute", "publication": "Earthquake Spectra", "publication_date": "2012-08", "series_number": "3", "volume": "28", "issue": "3", "pages": "859-883" }, { "id": "authors:9k6eg-y1q54", "collection": "authors", "collection_id": "9k6eg-y1q54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140902-132003857", "type": "article", "title": "Site Effects and Damage Patterns", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Ledezma", "given_name": "Christian", "clpid": "Ledezma-C" }, { "family_name": "Montalva", "given_name": "Gonzalo A.", "clpid": "Montalva-G-A" }, { "family_name": "Tassara", "given_name": "Andr\u00e9s", "clpid": "Tassara-A" }, { "family_name": "Mylonakis", "given_name": "George", "clpid": "Mylonakis-G" }, { "family_name": "Boroschekf", "given_name": "Ruben", "clpid": "Boroschekf-R" } ], "abstract": "A set of observations on site effects and damage patterns from the M_w 8.8 Maule, Chile, earthquake is presented, focusing on identification of structural damage variability associated with nonuniform soil conditions and subsurface geology. Observations are reported from: (1) the City of Santiago de Chile (Am\u00e9rico Vespucio Norte Ring Highway, Ciudad Empresarial business park), (2) the Municipality of Vi\u00f1a del Mar, and (3) the City of Concepci\u00f3n, extending over 600 km along the Chilean coast. Reconnaissance information and ground motion recordings from the megathrust event are combined with site investigation data in the regions of interest. Comparisons against macroseismic observations related to uneven damage distribution from the M_w 8.0 1985 Valpara\u00edso earthquake are discussed. Complexities associated with identifying the mechanics and underlying physical processes responsible for the manifestation of these effects are elucidated.", "doi": "10.1193/1.4000029", "issn": "8755-2930", "publisher": "Earthquake Engineering Research Institute", "publication": "Earthquake Spectra", "publication_date": "2012-06", "series_number": "S1", "volume": "28", "issue": "S1", "pages": "S55-S74" }, { "id": "authors:bv8jd-bq432", "collection": "authors", "collection_id": "bv8jd-bq432", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140904-161304282", "type": "article", "title": "Site- and ground motion dependent nonlinear effects in seismological model predictions", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Li", "given_name": "Wei", "orcid": "0000-0003-2543-2558", "clpid": "Li-Wei" } ], "abstract": "We investigate the empirical relationship between site response nonlinearity, soil properties, and ground motion characteristics, as a first step to enable efficient integration of nonlinear analyses in broadband ground motion simulations. For this purpose, we use 24 downhole array sites with detailed geotechnical information and subject the profiles to broadband ground motion synthetics. We quantify the extent of soil nonlinearity in site-specific response analyses by estimating the divergence between linear and nonlinear ground surface predictions. We show that the parameters controlling the nonlinear response are V_(S30) (weighted averaged shear wave velocity in the top 30 m of the soil profile), the site amplification at the fundamental frequency (Amp), the peak ground acceleration (PGA), and the frequency index (FI), a quantitative measure we define to characterize how well the incident motion can \"see\" the near-surface soil layers. Using the synthetic results, we quantitatively describe the error introduced in ground motion predictions when nonlinear effects are not accounted for, and show that the error is both site and ground motion dependent. Our study indicates that to characterize the susceptibility of a soil profile to nonlinear effects, V_(S30) should be complemented with measures of the soil\u2013rock impedance contrast, as well as measures of the ground motion intensity and frequency content.", "doi": "10.1016/j.soildyn.2011.06.013", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2012-01", "series_number": "1", "volume": "32", "issue": "1", "pages": "143-151" }, { "id": "authors:ajfms-ahx73", "collection": "authors", "collection_id": "ajfms-ahx73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140904-163138474", "type": "article", "title": "A Wavelet-based Seismogram Inversion Algorithm for the In Situ Characterization of Nonlinear Soil Behavior", "author": [ { "family_name": "Assimaki", "given_name": "D.", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Li", "given_name": "W.", "orcid": "0000-0003-2543-2558", "clpid": "Li-Wei" }, { "family_name": "Kalos", "given_name": "A.", "clpid": "Kalos-A" } ], "abstract": "We present a full waveform inversion algorithm of downhole array seismogram recordings that can be used to estimate the inelastic soil behavior in situ during earthquake ground motion. For this purpose, we first develop a new hysteretic scheme that improves upon existing nonlinear site response models by allowing adjustment of the width and length of the hysteresis loop for a relatively small number of soil parameters. The constitutive law is formulated to approximate the response of saturated cohesive materials, and does not account for volumetric changes due to shear leading to pore pressure development and potential liquefaction. We implement the soil model in the forward operator of the inversion, and evaluate the constitutive parameters that maximize the cross-correlation between site response predictions and observations on ground surface. The objective function is defined in the wavelet domain, which allows equal weight to be assigned across all frequency bands of the non-stationary signal. We evaluate the convergence rate and robustness of the proposed scheme for noise-free and noise-contaminated data, and illustrate good performance of the inversion for signal-to-noise ratios as low as 3. We finally employ the proposed scheme to downhole array data, and show that results compare very well with published data on generic soil conditions and previous geotechnical investigation studies at the array site. By assuming a realistic hysteretic model and estimating the constitutive soil parameters, the proposed inversion accounts for the instantaneous adjustment of soil response to the level and strain and load path during transient loading, and allows results to be used in predictions of nonlinear site effects during future events.", "doi": "10.1007/s00024-010-0198-6", "issn": "0033-4553", "publisher": "Springer", "publication": "Pure and Applied Geophysics", "publication_date": "2011-10", "series_number": "10", "volume": "168", "issue": "10", "pages": "1669-1691" }, { "id": "authors:a15nb-tkf23", "collection": "authors", "collection_id": "a15nb-tkf23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140902-140555218", "type": "article", "title": "Model for Dynamic Shear Modulus and Damping for Granular Soils", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Kausel", "given_name": "Eduardo", "clpid": "Kausel-E" }, { "family_name": "Whittle", "given_name": "Andrew", "clpid": "Whittle-A" } ], "abstract": "This paper presents a simple four-parameter model that can represent the shear modulus factors and damping coefficients for a granular soil subjected to horizontal shear stresses imposed by vertically propagating shear waves. The input parameters are functions of the confining pressure and density and have been derived from a generalized effective stress soil model referred to as MIT-S1. The predicted shear moduli and damping factors are in excellent agreement with high quality resonant column test data on remolded sands and confining pressures ranging from 30 kPa to 1.8 MPa. The proposed model has been implemented in a frequency domain computer code. By simulating the variations in stiffness and damping with confining pressure, the proposed model provides a more realistic simulation of ground amplification that does not filter out high frequency components of the base excitation.", "doi": "10.1061/(ASCE)1090-0241(2000)126:10(859)", "issn": "1090-0241", "publisher": "American Society of Civil Engineers", "publication": "Journal of Geotechnical and Geoenvironmental Engineering", "publication_date": "2010-10", "series_number": "10", "volume": "126", "issue": "10", "pages": "859-869" }, { "id": "authors:fet2d-ecs26", "collection": "authors", "collection_id": "fet2d-ecs26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140904-160952252", "type": "article", "title": "Site- and Motion-Dependent Parametric Uncertainty of Site-Response Analyses in Earthquake Simulations", "author": [ { "family_name": "Li", "given_name": "W.", "orcid": "0000-0003-2543-2558", "clpid": "Li-Wei" }, { "family_name": "Assimaki", "given_name": "D.", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" } ], "abstract": "We investigate the propagation of uncertainty in site-response analyses from the soil model parameters to the ground surface motion at three downhole array sites in the Los Angeles (LA) Basin. For this purpose, we develop realistic stochastic models of elastic and nonlinear dynamic soil properties using extensive site-specific and generic geotechnical data on the variability of soil properties. We also generate synthetic ground motions using a finite source dynamic rupture model over a wide range of magnitudes and distances and use this statistically significant number of ground motions in the analysis. For each of the three sites, we evaluate the effects of soil parameter uncertainty as a function of the seismic input intensity and frequency content. We show that the frequency range, where the ground-motion variability due to soil parameter uncertainty is maximized, is a function of both the site and the seismogram characteristics. We compare our results with previously published studies and show that different soil models, statistical descriptions of soil parameters, or ground-motion scenarios may yield substantial differences in the estimated site-response scatter. We conclude that the effects of nonlinear soil property uncertainties on the ground-motion variability strongly depend on the seismic motion intensity, and this dependency is more pronounced for soft soil profiles. By contrast, the effects of velocity profile uncertainties are less intensity dependent and more sensitive to the velocity impedance in the near surface that governs the maximum site amplification.", "doi": "10.1785/0120090030", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2010-06", "series_number": "3", "volume": "100", "issue": "3", "pages": "954-968" }, { "id": "authors:eftgh-f2s74", "collection": "authors", "collection_id": "eftgh-f2s74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140828-163417572", "type": "article", "title": "Quantifying Nonlinearity Susceptibility via Site-Response Modeling Uncertainty at Three Sites in the Los Angeles Basin", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Li", "given_name": "Wei", "orcid": "0000-0003-2543-2558", "clpid": "Li-Wei" }, { "family_name": "Steidl", "given_name": "Jamison", "clpid": "Steidl-J-H" }, { "family_name": "Schmedes", "given_name": "Jan", "clpid": "Schmedes-J" } ], "abstract": "The effects of near-surface soil stratigraphy on the amplitude and frequency content of ground motion are accounted for in most modern U.S. seismic design codes for building structures as a function of the soil conditions prevailing in the area of interest. Nonetheless, currently employed site-classification criteria do not adequately describe the nonlinearity susceptibility of soil formations, which prohibits the development of standardized procedures for the computationally efficient integration of nonlinear ground response analyses in broadband ground-motion simulations. In turn, the lack of a unified methodology for nonlinear site-response analyses affects both the prediction accuracy of site-specific ground-motion intensity measures and the evaluation of site-amplification factors when broadband simulations are used for the development of hybrid attenuation relations. In this article, we introduce a set of criteria for quantification of the nonlinearity susceptibility of soil profiles based on the site conditions and incident ground-motion characteristics, and we implement them to identify the least complex ground response prediction methodology required for the simulation of nonlinear site effects at three sites in the Los Angeles basin. The criteria are developed on the basis of a comprehensive nonlinear site-response modeling uncertainty analysis, which includes both detailed soil profile descriptions and statistical adequacy of ground-motion time histories. Approximate and incremental nonlinear models are implemented, and the limited site-response observations are initially compared to the ensemble site-response estimates. A suite of synthetic ground motions for rupture scenarios of weak, medium, and large magnitude events (M 3.5\u20137.5) is next generated, parametric studies are conducted for each fixed magnitude scenario by varying the source-to-site distance, and the variability introduced in ground-motion predictions is quantified for each nonlinear site-response methodology. A frequency index is developed to describe the frequency content of incident ground motion relative to the resonant frequencies of the soil profile, and this index is used in conjunction with the rock-outcrop acceleration peak amplitude (PGA_(RO)) to identify the site conditions and ground-motion characteristics where incremental nonlinear analyses should be employed in lieu of approximate methodologies. We show that the proposed intensity-frequency representation of ground motion may be implemented to describe the nonlinearity susceptibility of soil formations in broadband simulations by accounting both for the magnitude-distance-orientation characteristics of seismic motion and the profile stiffness characteristics. The synthetic ground-motion predictions are next used for the development of site-amplification factors for the alternative site-response methodologies, and the results are compared to published site factors of attenuation relations. For the site conditions investigated, currently established amplification factors compare well with synthetic simulations for class C and D site conditions, while long-period amplification factors are overestimated by a factor of 1.5 at the class E site, where site-specific nonlinear analyses should be employed for levels of PGA_(RO)>0.2g.", "doi": "10.1785/0120080031", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2008-10", "series_number": "5", "volume": "98", "issue": "5", "pages": "2364-2390" }, { "id": "authors:a1b31-e3555", "collection": "authors", "collection_id": "a1b31-e3555", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140828-164055754", "type": "article", "title": "Site Amplification and Attenuation via Downhole Array Seismogram Inversion: A Comparative Study of the 2003 Miyagi-Oki Aftershock Sequence", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Li", "given_name": "Wei", "orcid": "0000-0003-2543-2558", "clpid": "Li-Wei" }, { "family_name": "Steidl", "given_name": "Jamison H.", "clpid": "Steidl-J-H" }, { "family_name": "Tsuda", "given_name": "Kenichi", "clpid": "Tsuda-K" } ], "abstract": "Weak-motion geotechnical array recordings at 38 stations of the Japanese strong-motion network KiK-Net from the 2003 M_w 7:0 Miyagi-Oki aftershock sequence are used here to quantify the amplification and attenuation effects of near-surface formations to incident seismic motion. Initially, a seismic waveform optimization algorithm is implemented for the evaluation of high-resolution, low-strain velocity (V_s), attenuation (Q_s), and density (\u03c1) profiles at the sites of interest. Based on the inversion results, V_s versus Q_s correlations are developed, and scattering versus intrinsic attenuation effects are accounted for in their physical interpretation. Surface-to-downhole traditional spectral ratios (SSR), cross-spectral ratios (c-SSR), and horizontal-to-vertical (H/V) site-response estimates are next evaluated and compared,\nwhile their effectiveness is assessed as a function of the site conditions classified on the basis of the weighted average Vs of the upper 30 m (V_(s30)) of the formations.\nSingle and reference-station site-response estimates are successively compared to surface-to-rock outcrop amplification spectra and are evaluated by deconvolution\nof the downhole records based on the inversion results; comparison of the observed SSR and estimated surface-to-rock outcrop amplification spectra illustrates the effects\nof destructive interference of downgoing waves at the downhole instrument level as a function of the site class. Site amplification factors are successively computed in reference to the National Earthquake Hazards Reduction Program (NEHRP) B\u2013C boundary site conditions (V_(s30) = 760 m/sec), and results are compared to published values\ndeveloped on the basis of strong-motion data and site-response analyses. Finally, weak-motion SSR estimates are compared to the mainshock spectra, and conclusions\nare drawn for the implications of soil nonlinearity in the near surface. Results presented in this article suggest that currently employed site classification criteria need\nto be reevaluated to ensure intraclass consistency in the assessment of amplification potentials and nonlinearity susceptibility of near-surficial soil formations.", "doi": "10.1785/0120070030", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2008-02", "series_number": "1", "volume": "98", "issue": "1", "pages": "301-330" }, { "id": "authors:67wnz-yv987", "collection": "authors", "collection_id": "67wnz-yv987", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140828-161953655", "type": "article", "title": "Modified Topographic Amplification Factors for a Single Faced Slope due to Kinematic Soil-Structure Interaction", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Kausel", "given_name": "Eduardo", "clpid": "Kausel-E" } ], "abstract": "In this paper, we evaluate the additive effects of topography, soil nonlinearity, and soil-structure interaction SSI along the crest of an idealized 40 m high cliff-type topographic feature with slope inclination 300, where excessive damage was observed during the Athens 1999 earthquake. The objective of this paper is to investigate the relative contribution of topographic amplification, and kinematic SSI as a function of the incident motion frequency content and geotechnical site conditions for a surface and an embedded structure located at the cliff crest. For this purpose, we perform elastic parametric and nonlinear site-specific two-dimensional finite element\nsimulations using three profiles and six input motions. We illustrate the role of SSI in altering the response at the location of peak topographic amplification potential behind the crest, the effects of incident motion incoherency on the transient structural response, and the beneficial contribution of structural embedment. We finally suggest that empirical models for base-slab averaging of shallow foundations, developed as a function of site conditions, structural dimensions and center line location, could be combined with topographic amplification factors to predict realistic design spectra for structures located on irregular topographic features.", "doi": "10.1061/(ASCE)1090-0241(2007)133:11(1414)", "issn": "1090-0241", "publisher": "ASCE", "publication": "Journal of Geotechnical and Geoenvironmental Engineering", "publication_date": "2007-11", "series_number": "11", "volume": "133", "issue": "11", "pages": "1414-1431" }, { "id": "authors:5wb3j-6xh03", "collection": "authors", "collection_id": "5wb3j-6xh03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140902-135451772", "type": "article", "title": "Wave propagation and soil\u2013structure interaction on a cliff crest during the 1999 Athens Earthquake", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Kausel", "given_name": "Eduardo", "clpid": "Kausel-E" }, { "family_name": "Gazetas", "given_name": "George", "clpid": "Gazetas-G" } ], "abstract": "During the 1999 Athens Earthquake the town of Ad\u00e0mes, located on the eastern cliff of the Kifissos river canyon, experienced unexpectedly heavy damage. Despite the significant amplification potential of the slope geometry, topography effects cannot alone explain the uneven damage distribution within a 300 m zone behind the crest, characterized by a rather uniform structural quality. This paper illustrates the important role of soil stratigraphy, material heterogeneity, and soil\u2013structure interaction on the characteristics of ground surface motion. For this purpose, we first perform elastic two-dimensional wave propagation analyses utilizing available geotechnical and\nseismological data, and validate our results by comparison with aftershock recordings. We then conduct non-linear time-domain simulations that include spatial variability of soil properties and soil\u2013structure interaction effects, to reveal their additive contribution in the topographic motion aggravation.", "doi": "10.1016/j.soildyn.2004.11.031", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2005-08", "series_number": "7-10", "volume": "25", "issue": "7-10", "pages": "513-527" }, { "id": "authors:yep5y-c7e64", "collection": "authors", "collection_id": "yep5y-c7e64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140902-133617423", "type": "article", "title": "Effects of Local Soil Conditions on the Topographic Aggravation of Seismic Motion: Parametric Investigation and Recorded Field Evidence from the 1999 Athens Earthquake", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Gazetas", "given_name": "George", "clpid": "Gazetas-G" }, { "family_name": "Kausel", "given_name": "Eduardo", "clpid": "Kausel-E" } ], "abstract": "During the 1999 Athens earthquake, the town of Ad\u00e0mes, located on the eastern side of the Kifissos river canyon, experienced unexpectedly heavy damage. Despite the particular geometry of the slope that caused significant motion amplification, topography effects alone cannot explain the uneven damage distribution within a 300-m zone parallel to the canyon's crest, which is characterized by a rather uniform structural quality. In this article, we illustrate the important role of soil stratigraphy and material heterogeneity on the topographic aggravation of surface ground motion. For this purpose, we first conduct an extensive time-domain parametric study using idealized stratified profiles and Gaussian stochastic fields to characterize the spatial distribution of soil properties, and using Ricker wavelets to describe the seismic input motion; the results show that both topography and local soil conditions significantly affect the spatial variability of seismic motion. We next perform elastic two-dimensional wave propagation analyses based on available local geotechnical and seismological data and validate our results by comparison with aftershock recordings.", "doi": "10.1785/0120040055", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2005-06", "series_number": "3", "volume": "95", "issue": "3", "pages": "1059-1089" }, { "id": "authors:fqyg0-p4p14", "collection": "authors", "collection_id": "fqyg0-p4p14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140902-132944755", "type": "article", "title": "Soil and Topographic Amplification on Canyon Banks and the 1999 Athens Earthquake", "author": [ { "family_name": "Assimaki", "given_name": "D.", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Gazetas", "given_name": "G.", "clpid": "Gazetas-G" } ], "abstract": "A time-domain parametric study for the seismic response of a region located on the eastern bank of the Kifisos river canyon is performed to evaluate the significance of topography and soil effects on the seismic response of slopes. This region experienced unexpectedly heavy damage during the 7 September 1999 M_s 5.9 earthquake. Two-dimensional finite-element and spectral-element analyses are conducted using Ricker wavelets of various central frequencies as horizontal and vertical base excitation. The significance of a layered soil profile and the frequency content of the input motion, the emergence of \"parasitic\" acceleration components, and the effect of the angle of incidence on the amplification of the incoming waves are all discussed in detail. It is shown that the presence of a surface soil layer significantly affects the amplification pattern. The so-called Topographic Aggravation Factor (defined as the 2D/1D Fourier spectral ratio) achieves its maximum value very near the crest, in function of the frequency content of the excitation. For the particular soil conditions and geometry analysed, vertically propagating SV waves incite at about the critical angle, resulting in the highest topographic amplification.", "doi": "10.1142/S1363246904001250", "issn": "1363-2469", "publisher": "World Scientific Publishing", "publication": "Journal of Earthquake Engineering", "publication_date": "2004-01", "series_number": "1", "volume": "8", "issue": "1", "pages": "1-43" }, { "id": "authors:amba5-ygb32", "collection": "authors", "collection_id": "amba5-ygb32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140902-134438693", "type": "article", "title": "An equivalent linear algorithm with frequency- and pressure-dependent moduli and damping for the seismic analysis of deep sites", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Kausel", "given_name": "Eduardo", "clpid": "Kausel-E" } ], "abstract": "The seismic analysis of soil deposits is most often carried out with an iterative computational scheme, proposed by Seed and Idriss, in which inelastic effects are only approximately modeled through soil degradation curves. Laboratory experimental data indicate that for highly confined materials, the standardized reduction curves commonly used overestimate the capacity of soils to dissipate energy. This paper first presents the results obtained with a simple four-parameter constitutive soil model, which when used to simulate cyclic loading, produces results that agree well with available laboratory experiments for soils under arbitrarily large confining pressures. Thereafter, a frequency- and pressure-dependent iterative algorithm for seismic amplification is proposed, which provides time histories that match well the results obtained with a true non-linear model. Finally, the modified linear iterative analysis is successfully used for the seismic analysis of a 1 km deep model for the Mississippi embayment near Memphis, Tennessee, and a class-A prediction of the seismic amplification in Treasure Island during the Loma Prieta earthquake.", "doi": "10.1016/S0267-7261(02)00120-3", "issn": "0267-7261", "publisher": "Elsevier", "publication": "Soil Dynamics and Earthquake Engineering", "publication_date": "2002-10", "series_number": "9-12", "volume": "22", "issue": "9-12", "pages": "959-965" }, { "id": "authors:dgb7b-ksr38", "collection": "authors", "collection_id": "dgb7b-ksr38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140902-135902738", "type": "article", "title": "Model for Dynamic Shear Modules and Damping for Granular Soils", "author": [ { "family_name": "Assimaki", "given_name": "Dominic", "orcid": "0000-0002-3008-8088", "clpid": "Asimaki-D" }, { "family_name": "Kausel", "given_name": "Eduardo", "clpid": "Kausel-E" }, { "family_name": "Whittle", "given_name": "Andrew", "clpid": "Whittle-A" } ], "abstract": "This paper presents a simple four-parameter model that can represent the shear modulus factors and damping coefficients for a granular soil subjected to horizontal shear stresses imposed by vertically propagating shear waves. The input parameters are functions of the confining pressure and density and have been derived from a generalized effective stress soil model referred to as MIT-S1. The predicted shear moduli and damping factors are in excellent agreement with high quality resonant column test data on remolded sands and confining pressures ranging from 30 kPa to 1.8 MPa. The proposed model has been implemented in a frequency domain computer code. By simulating the variations in stiffness and damping with confining pressure, the proposed model provides a more realistic simulation of ground amplification that does not filter out high frequency components of the base excitation.", "doi": "10.1061/(ASCE)1090-0241(2000)126:10(859)", "issn": "1090-0241", "publisher": "ASCE", "publication": "Journal of Geotechnical and Geoenvironmental Engineering", "publication_date": "2000-10", "series_number": "10", "volume": "126", "issue": "10", "pages": "859-869" } ]