Article records
https://feeds.library.caltech.edu/people/Harkrider-D-G/article.rss
A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenFri, 12 Apr 2024 13:42:10 +0000A fast, convenient program for computation of surface-wave dispersion curves in multilayered media
https://resolver.caltech.edu/CaltechAUTHORS:20140801-141421373
Authors: {'items': [{'id': 'Press-F', 'name': {'family': 'Press', 'given': 'Frank'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David'}}, {'id': 'Seafeldt-C-A', 'name': {'family': 'Seafeldt', 'given': 'C. A.'}}]}
Year: 1961
Surface wave analysis has become an important tool for exploration of crustal and mantle structure. The need exists for fast, convenient digital computer programs for computing theoretical dispersion curves and displacements for Rayleigh waves and Love waves. One such program for an IBM 7090 computer is described and made available to the scientific community. Among the conveniences are mail-order service, high speed, and choice of many options.https://authors.library.caltech.edu/records/cfzhc-d9z63Computation of surface wave dispersion for multilayered anisotropic media
https://resolver.caltech.edu/CaltechAUTHORS:20140429-150117709
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}, {'id': 'Anderson-D-L', 'name': {'family': 'Anderson', 'given': 'Don L.'}}]}
Year: 1962
With the program described in this paper it is now possible to compute surface wave dispersion in a solid heterogeneous halfspace containing up to 200 anisotropic layers.
Certain discrepancies in surface wave observations, such as disagreement between Love and Rayleigh wave data and other independent evidence, suggest that anisotropy may be important in some seismological problems. In order to study the effect of anisotropy on surface wave dispersion a program was written for an IBM 7090 computer which will compute dispersion curves and displacements for Rayleigh waves in a layered halfspace in which each layer is transversely isotropic. A simple redefinition of parameters makes it possible to use existing programs to compute Love wave dispersion.https://authors.library.caltech.edu/records/vgpm1-8y778Propagation of acoustic-gravity waves in the atmosphere
https://resolver.caltech.edu/CaltechAUTHORS:20160224-082257812
Authors: {'items': [{'id': 'Press-F', 'name': {'family': 'Press', 'given': 'Frank'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David'}}]}
Year: 1962
DOI: 10.1029/JZ067i010p03889
Homogeneous wave guide theory is used to derive dispersion curves, vertical pressure distributions, and synthetic barograms for atmospheric waves. A complicated mode structure is found involving both gravity and acoustic waves. Various models of the atmosphere are studied to explore seasonal and geographic effects on pulse propagation. The influence of different zones in the atmosphere on the character of the barograms is studied. It is found that the first arriving waves are controlled by the properties of the lower atmospheric channel. Comparison of theoretical results and experimental data from large thermonuclear explosions is made in the time and frequency domains, and the following conclusions are reached: (1) The major features on barograms are due to dispersion; (2) superposition of several modes is needed to explain observed features; (3) scatter of data outside the range permitted by extreme atmospheric models shows the influence of winds for A1; wind effects and higher modes are less important for A_2 waves. A discussion is included on atmospheric terminations and how these affect dispersion curves.https://authors.library.caltech.edu/records/v4hkw-dsh24On detecting soft layers in the mantle with Rayleigh waves
https://resolver.caltech.edu/CaltechAUTHORS:20140801-144123624
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}, {'id': 'Hales-A-L', 'name': {'family': 'Hales', 'given': 'A. L.'}}, {'id': 'Press-F', 'name': {'family': 'Press', 'given': 'F.'}}]}
Year: 1963
DOI: 10.1785/BSSA0530030539
The feasibility of an experiment to detect soft or molten zones in the mantle using Rayleigh wave phase velocities is examined. It is found that when the anomalous zone has large lateral extent the phase velocity curves are so affected as to make it easily detectable. A discussion of dispersion curves and displacement with depth is presented. A pseudo-flexural mode of oscillation is found to be possible for the layers above a molten zone.https://authors.library.caltech.edu/records/3dkm8-cst09Surface waves in multilayered elastic media. I. Rayleigh and Love waves from buried sources in a multilayered elastic half-space
https://resolver.caltech.edu/CaltechAUTHORS:20140801-145851766
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1964
DOI: 10.1785/BSSA0540020627
A matrix formulation is used to derive integral expressions for the time transformed displacement fields produced by simple sources at any depth in a multilayered elastic isotropic solid half-space. The integrals are evaluated for their residue contribution to obtain surface wave displacements in the frequency domain. The solutions are then generalized to include the effect of a surface liquid layer. The theory includes the effect of layering and source depth for the following: (1) Rayleigh waves from an explosive source, (2) Rayleigh waves from a vertical point force, (3) Rayleigh and Love waves from a vertical strike slip fault model. The latter source also includes the effect of fault dimensions and rupture velocity. From these results we are able to show certain reciprocity relations for surface waves which had been previously proved for the total displacement field. The theory presented here lays the ground work for later papers in which theoretical seismograms are compared with observations in both the time and frequency domain.https://authors.library.caltech.edu/records/wtxn4-z1326Radiation patterns of seismic surface waves from buried dipolar point sources in a flat stratified Earth
https://resolver.caltech.edu/CaltechAUTHORS:20160224-080724513
Authors: {'items': [{'id': 'Ben-Menahem-A', 'name': {'family': 'Ben-Menahem', 'given': 'Ari'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1964
DOI: 10.1029/JZ069i012p02605
Explicit compact expressions were obtained for the far displacement field of Rayleigh and Love waves generated by force configurations which served to simulate shear-type faults with arbitrary dip and slip. The medium transfer functions for dipolar sources were computed for a Gutenberg flat continental earth model with 23 layers. These were then used to obtain universal radiation pattern charts for couple- and double-couple-type sources at various depths over the period range 50 to 350 sec. It was demonstrated by means of few typical examples that the radiation patterns of Rayleigh waves may depend strongly on the depth of the source, and unlike the fundamental Love mode may be rather sensitive to small variations in frequency. For a given source and frequency the radiation pattern may differ considerably from one mode to another.https://authors.library.caltech.edu/records/9t56a-rkz44Determination of source parameters of explosions and earthquakes by amplitude equalization of seismic surface waves: 1. Underground nuclear explosions
https://resolver.caltech.edu/CaltechAUTHORS:20151021-150137211
Authors: {'items': [{'id': 'Toksöz-M-N', 'name': {'family': 'Toksöz', 'given': 'M. N.'}}, {'id': 'Ben-Menahem-A', 'name': {'family': 'Ben-Menahem', 'given': 'A.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}]}
Year: 1964
DOI: 10.1029/JZ069i020p04355
A method of determining the source parameters of explosions and earthquakes from the amplitude spectrums of seismic surface waves is described. The method, called amplitude equalization, involves the correction of the ground displacement spectrum for the propagation effect. This is accomplished by multiplying it numerically with the inverse of the frequency response of the layered medium. The result is the amplitude spectrum of the source function, which may be interpreted by itself or jointly with the initial phase spectrum to determine the source-time variation. The spectrums of the Rayleigh waves from underground nuclear explosions are compared and the source-time function is interpreted using the amplitude equalization method. The time variation of the pressure pulse at the boundary of the elastic zone is found to be of the form p(t) = P_0te^(−ηt), where η is a parameter which depends on the yield of the explosion and on the medium. For the events studied, the breadth of the pulse increased (η decreased) with the yield of the explosion.https://authors.library.caltech.edu/records/48smn-wzh74Theoretical and observed acoustic-gravity waves from explosive sources in the atmosphere
https://resolver.caltech.edu/CaltechAUTHORS:20160224-081435265
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1964
DOI: 10.1029/JZ069i024p05295
A matrix formulation is used to derive the pressure variation for acoustic-gravity waves from an explosive source in an atmosphere modeled by a large number of isothermal layers. Comparison of theoretical and observed barograms from large thermonuclear explosions leads to the following conclusions: (1) The major features on the barogram can be explained by the superposition of four modes, (2) different parts of the vertical temperature structure of the atmosphere control the relative excitation of these modes, (3) a scaled point source is sufficient to model thermonuclear explosions, (4) the observed shift in dominance of certain frequencies with yield and altitude can be explained by means of the empirical scaling laws derived from the direct wave near the explosion, and (5) out to 50° from the source, the observed variation of amplitude with distance can be accounted for by geometrical spreading over a spherical surface.https://authors.library.caltech.edu/records/b6wrf-seq91Determination of source parameters by amplitude equalization of seismic surface waves: 2. Release of tectonic strain by underground nuclear explosions and mechanisms of earthquakes
https://resolver.caltech.edu/CaltechAUTHORS:20150928-113442846
Authors: {'items': [{'id': 'Toksöz-M-N', 'name': {'family': 'Toksöz', 'given': 'M. Nafi'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}, {'id': 'Ben-Menahem-A', 'name': {'family': 'Ben-Menahem', 'given': 'Ari'}}]}
Year: 1965
DOI: 10.1029/JZ070i004p00907
The radiation patterns of Love and Rayleigh waves from three nuclear explosions (Hardhat, Haymaker, and Shoal) are studied to determine the nature of the asymmetry of radiation and the mechanism of Love wave generation. From a comparative study of different explosions it is reasoned that the Love waves are generated at the source of the explosion. The source function, represented as the superimposition of an isotropic dilatational component due to the explosion and a multipolar component due to the release of tectonic strain energy, is consistent with the observed radiation patterns and the amplitude spectrums. The amount of seismic energy due to the strain release is computed. In some cases (Haymaker and Shoal) it is found that this energy may be due to the relaxation of the pre-stressed medium by the explosion-formed cavity. In the case of Hardhat it is concluded that the explosion must have triggered some other strain release mechanism, such as an earthquake. The amplitude equalization method is applied to surface waves from an earthquake to determine the source parameters. From only the amplitude spectrums and radiation patterns of Love and Rayleigh waves, the source functions, source depth, strike and dip of the fault plane, and the rake of displacement are determined for the July 20, 1964, Fallon earthquake.https://authors.library.caltech.edu/records/6jsew-h6w02Reply [to "Comments on paper by David G. Harkrider, 'Theoretical and observed acoustic-gravity waves from explosive sources in the atmosphere'"]
https://resolver.caltech.edu/CaltechAUTHORS:20160224-084445240
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}]}
Year: 1965
DOI: 10.1029/JZ070i010p02465
I acknowledge and agree with the comments made on Harkrider [1964] by A.D. Pierce.https://authors.library.caltech.edu/records/6hzbm-2s158A note on the existence of relative maxima and minima on phase velocity curves
https://resolver.caltech.edu/CaltechAUTHORS:20140801-163614863
Authors: {'items': [{'id': 'Thrower-E-N', 'name': {'family': 'Thrower', 'given': 'E. N.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}]}
Year: 1965
DOI: 10.1785/BSSA0550060971
Phase and group velocity dispersion curves for fundamental Rayleigh waves have been computed with more precision than previously attempted. The new curves show a relative minimum in phase velocity at periods near 50 sec for four perturbed Gutenberg continental models.https://authors.library.caltech.edu/records/5q6b6-41h69Surface Wave Energy from Point Sources in Plane Layered Earth Models
https://resolver.caltech.edu/CaltechAUTHORS:20140507-144951811
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}, {'id': 'Anderson-D-L', 'name': {'family': 'Anderson', 'given': 'Don L.'}}]}
Year: 1966
DOI: 10.1029/JZ071i012p02967
The total energy contained in a surface wave can be computed from its propagation-corrected spectrum by integrating over the surface of the earth and over the depth of the wave guide. The former requires knowledge of the radiation pattern of the source. The latter requires only a knowledge of the variation of physical properties with depth. In this paper the depth integration is performed for a continental and an oceanic earth model for three Rayleigh modes and four Love modes. The results are presented in tables and graphs in such a way that it is convenient to convert an observed surface wave displacement or displacement spectrum to total energy density. If the surface radiation pattern is known, the surface integration then yields the total energy in the observed spectrum. The partioning of energy between surface wave modes is computed for several simple sources at the surface and at depth, making it possible to estimate the energy contained in frequency bands or modes which are inaccessible for direct analysis. The increasing importance of the higher modes in the total energy budget at short periods and for channel depth sources is demonstrated. The shapes of the spectrums are diagnostic of source orientation and depth.https://authors.library.caltech.edu/records/4b02k-kc654Air-Sea Waves from the Explosion of Krakatoa
https://resolver.caltech.edu/CaltechAUTHORS:20150928-113055558
Authors: {'items': [{'id': 'Press-F', 'name': {'family': 'Press', 'given': 'Frank'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David'}}]}
Year: 1966
DOI: 10.1126/science.154.3754.1325
The distant sea disturbances which followed the explosion of Krakatoa are correlated with recently discovered atmospheric acoustic and gravity modes having the same phase velocity as long waves on the ocean. The atmospheric waves jumped over the land barriers and reexcited the sea waves with amplitudes exceeding the hydrostatic values. An explosion of 100 to 150 megatons would be required to duplicate the Krakatoa atmospheric pressure pulse.https://authors.library.caltech.edu/records/xvvaz-4pv10The Krakatoa Air-Sea Waves: an Example of Pulse Propagation in Coupled Systems
https://resolver.caltech.edu/CaltechAUTHORS:20150930-150859552
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David'}}, {'id': 'Press-F', 'name': {'family': 'Press', 'given': 'Frank'}}]}
Year: 1967
DOI: 10.1111/j.1365-246X.1967.tb02150.x
The theory of pulse propagation in an atmosphere coupled to an ocean is applied to the air-sea waves excited by the explosion of the volcano Krakatoa. Numerical results for a realistic atmosphere-ocean system show that the principal air pulse corresponds to the fundamental gravity mode GR_0. A small sea wave is associated with the mode GW_0 with phase velocities close to the √(gh) velocity of the ocean. Free waves with this velocity exist in the atmosphere and transfer energy to the ocean in an efficient manner. These air waves 'jump' over land barriers and re-excite the sea waves. An explosion of 100–150 megatons is required to produce the equivalent of the Krakatoa pressure disturbance.https://authors.library.caltech.edu/records/r42n3-t2639The perturbation of Love wave spectra
https://resolver.caltech.edu/CaltechAUTHORS:20150928-112326951
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1968
The equations governing the variational principles for Love wave spectra are investigated. It is shown that assumptions used by earlier authors are not necessary to the validity of the variational techniques.
Moreover it is demonstrated that except for a homogeneous plate, these assumptions are false for plane multilayered media and lead to incorrect expressions for group-velocity perturbations. The correct expressions are determined and examples of their use are given.https://authors.library.caltech.edu/records/jewd8-1g690Comparison of theoretical Rayleigh waves generated by atmospheric explosions over an oceanic and a continental model
https://resolver.caltech.edu/CaltechAUTHORS:20151015-105027596
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}, {'id': 'Flinn-E-A', 'name': {'family': 'Flinn', 'given': 'Edward A.'}}]}
Year: 1968
DOI: 10.1785/gssrl.39.3-4.5
The matrix formulation for coupling an atmosphere-ocean system to the
solid earth will be presented, This theory allows one to calculate the excitation of air and sea waves from subsurface sources and the excitation of
Rayleigh waves from atmospheric and oceanic sources, As an example, theoretical Rayleigh waves are synthesized for two multilayered earth models, an oceanic and a continental structure. The sources are atmospheric explosions at various altitudes. A comparison is made of the fundamental and first higher mode as a function of source height and earth model below the source.https://authors.library.caltech.edu/records/h82d7-wkj11Universal dispersion tables II. Variational parameters for amplitudes, phase velocity and group velocity for first four Love modes for an oceanic and a continental earth model
https://resolver.caltech.edu/CaltechAUTHORS:20140429-151305372
Authors: {'items': [{'id': 'Anderson-D-L', 'name': {'family': 'Anderson', 'given': 'Don L.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1968
The universal dispersion theory, presented in Part I, is extended to allow computation of group velocity and amplitude partial derivatives. Tables giving the effect of a change in any parameter on phase velocity, group velocity and amplitude are given for two earth models, one oceanic and one continental shield. Tables are given for the fundamental and first three higher Love modes.
These tables make it possible to compute dispersion parameters for the first four Love modes for any realistic earth model or to invert observations to an earth model. Attenuation of Love waves for an arbitrary distribution of Q versus depth can also be computed by using techniques previously described.https://authors.library.caltech.edu/records/dpv28-w5875Fast evaluation of source parameters from isolated surface-wave signals. Part I. Universal tables
https://resolver.caltech.edu/CaltechAUTHORS:20150928-104929454
Authors: {'items': [{'id': 'Ben-Menahem-A', 'name': {'family': 'Ben-Menahem', 'given': 'Ari'}}, {'id': 'Rosenman-M', 'name': {'family': 'Rosenman', 'given': 'Martin'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1970
Tables for spectral displacements of seismic surface waves from shear dislocations in flat multilayered earth models were prepared. Earth response functions for seven modes (R_(11), R_(21), R_(12), L_0, L_1, L_2, L_3) at six periods (300 sec, 250 sec, 200 sec, 150 sec, 100 sec, 50 sec) and three paths (continental, oceanic, shield) were calculated for the source-depth range of 10 to 600 km at intervals of 5 km until 200 km, and thereafter at intervals of 10 km. Ground motion is given in micron-seconds for the three fundamental shear dislocations, each of strength U_0dS = 10^3 (m × km^2) and a delta-function time-dependence.
The tables provide the means for rapid evaluation of source parameters from spectral radiation patterns of amplitudes and initial phases.https://authors.library.caltech.edu/records/wh10a-3r878Effect of crustal structure on Rayleigh waves generated by atmospheric explosions
https://resolver.caltech.edu/CaltechAUTHORS:20151015-111100840
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}, {'id': 'Flinn-E-A', 'name': {'family': 'Flinn', 'given': 'Edward A.'}}]}
Year: 1970
DOI: 10.1029/RG008i003p00501
Theoretical seismograms are calculated at a teleseismic distance from atmospheric sources over oceanic and continental earth models. Vertical surface displacements of the fundamental and first higher-mode Rayleigh waves are obtained for each of the models. Source altitudes range from 0.3 to 4.88 km for a 1-kiloton nuclear explosion in a stratified thermal atmosphere. At 20-sec period, an explosion over the oceanic model exhibits amplitudes an order of magnitude greater than the equivalent amplitudes from an explosion of the same burst height and yield over any of the three continental structures. If the differences in anelastic attenuation over the paths are included, this effect will be reversed at large enough distances.https://authors.library.caltech.edu/records/z103k-wgb60Surface waves in multilayered elastic media. Part II. Higher mode spectra and spectral ratios from point sources in plane layered Earth models
https://resolver.caltech.edu/CaltechAUTHORS:20150928-105612764
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1970
Phase and amplitude spectra of Rayleigh and Love waves are presented for two Earth models, one oceanic and one continental shield. The spectra of the first three Rayleigh modes and the first four Love modes are tabulated for point sources at selected depths. These tables along with computer algorithms described here allow one to estimate the amplitude spectra at nontabulated source depths.
The use of spectral ratios as a means of determining source depth is investigated. A source depth of 20 km is obtained for the Fallon earthquake of July 20 1962. This depth agrees with previous estimates but the technique requires a fault-plane orientation which differs from radiation pattern solutions.https://authors.library.caltech.edu/records/d6h6f-10n27Theoretical acoustic gravity waves and Rayleigh waves generated by underground explosions
https://resolver.caltech.edu/CaltechAUTHORS:20151029-080919144
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}]}
Year: 1971
Theoretical barograms have been calculated for acoustic-gravity waves
generated by underground explosions. Two formulations were used. 1) The
thermally modeled gravitating atmosphere is excited by a time varying deformation of the earth's surface. The final deformation is the static
surface displacement due to a point pressure source at depth in an elastic
half-space. 2) The same atmosphere overlying a multilayered half-space
is excited by a point pressure source at depth in the solid medium.https://authors.library.caltech.edu/records/cak7n-atm39Acoustic-Gravity Wave Calculations in a Layer with a Linear Temperature Variation
https://resolver.caltech.edu/CaltechAUTHORS:20160224-080152448
Authors: {'items': [{'id': 'Greenfield-R-J', 'name': {'family': 'Greenfield', 'given': 'Roy J.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1971
DOI: 10.1111/j.1365-246X.1971.tb03405.x
An exact expression is obtained for the acoustic-gravity layer matrix for an atmospheric layer having a linear temperature variation. Expressions are also derived for the layer derivative matrices needed to calculate group velocity and mode excitation. The method requires the evaluation of confluent hypergeometric functions, whose series representations are rapidly convergent for layers, such as the lower thermosphere, which have large temperature gradients. The procedure allows rapid accurate calculations in studies of acoustic gravity wave propagation. The new procedure is used to calculate phase and group velocities for the GR_o mode at periods between 5 and 12 min and gives a change in these velocities of 0.3 per cent as compared with Press and Harkrider's results.https://authors.library.caltech.edu/records/hah8t-k3b57Seismic Source Descriptions of Underground Explosions and a Depth Discriminate
https://resolver.caltech.edu/CaltechAUTHORS:20151029-082401562
Authors: {'items': [{'id': 'Helmberger-D-V', 'name': {'family': 'Helmberger', 'given': 'D. V.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}]}
Year: 1972
DOI: 10.1111/j.1365-246X.1972.tb02358.x
Synthetic seismograms of both body waves and Rayleigh waves are used to determine the radiation field of a few large contained underground explosions. A number of possible source descriptions are investigated. A reduced displacement potential of the form, ø(t) = ø_0t^ξ exp(-ηt), fits the long- and short-period data. The source parameters appropriate for the Boxcar event are ξ = 0·5 and η = 0·15. Synthetic PL and Rayleigh waves are compared with observations from a number of different size events to determine the dependence of η on yield.
The amplitude of the long period synthetic body wave responses at ranges greater than about 12° increases rapidly as the source depth is increased. Thus the difference in spectral properties of explosions and earthquakes can be largely explained by the depth effect. The theoretical ratio SP/LP, that is the short period divided by the long-period amplitude, is computed from 12 to 25° for the Johnson upper mantle model and the Boxcar source. A study of an earthquake which cannot be distinguished from an explosion using the m_b vs. M_s criterion is investigated by the SP/LP discriminate.https://authors.library.caltech.edu/records/7ds6x-ecj86Precision of the determination of focal depth from the spectral ratio of Love/Rayleigh surface waves
https://resolver.caltech.edu/CaltechAUTHORS:20140812-115237990
Authors: {'items': [{'id': 'Massé-R-P', 'name': {'family': 'Massé', 'given': 'Robert P.'}}, {'id': 'Lambert-D-G', 'name': {'family': 'Lambert', 'given': 'D. G.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1973
The precision with which the focal depth may be determined using Love/Rayleigh-wave spectral ratios depends on the accuracy of the models for Earth structure and for source mechanism used in the focal depth calculations. Estimates of the precision of the focal depth determination are obtained using the partial derivatives of Love/Rayleigh spectral ratios with respect to the parameters: focal depth, shear velocity, dip angle, and slip angle. We find that errors caused by imprecise knowledge of any of these parameters can be important in practice.https://authors.library.caltech.edu/records/e7mtc-vxv09Theoretical Effect of Yield and Burst Height of Atmospheric Explosions on Rayleigh Wave Amplitudes
https://resolver.caltech.edu/CaltechAUTHORS:20151015-111535026
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}, {'id': 'Newton-C-A', 'name': {'family': 'Newton', 'given': 'C. A.'}}, {'id': 'Flinn-E-A', 'name': {'family': 'Flinn', 'given': 'E. A.'}}]}
Year: 1974
DOI: 10.1111/j.1365-246X.1974.tb03632.x
Theoretical seismograms for fundamental mode Rayleigh waves were calculated for atmospheric point sources over oceanic and over continental Earth models, as recorded at an epicentral distance of 10000 km. Yields were uniformly distributed over the range 1 kT-10 MT, for source altitudes in the range 0.3-92.0 km. The Earth structures used were those of Gutenberg and of Anderson and Toksöz. The source models were point mass-injection and energy-injection sources at altitude, as well as a distributed pressure pulse at the surface of the Earth.
It was found that: (1) as far as Rayleigh wave excitation is concerned, the mass-injection and energy-injection sources are equivalent; (2) for low altitudes the Rayleigh wave excitation is independent of source type, but at intermediate altitudes the surface overpressure source predicts greater amplitudes than the other two source models; (3) for most altitudes, the energy coupling from the atmosphere into Rayleigh waves is more efficient for the continental Earth structure than for the oceanic structure; (4) Rayleigh wave amplitude is more sensitive to yield than to burst height (5) dependence of Rayleigh wave amplitude is less than the cube root relation for low-yield explosions at intermediate altitudes but greater for high-yield explosions at near-surface altitudes; (6) spectral splitting ratios do not show a systematic variation with yield and burst height.https://authors.library.caltech.edu/records/3q409-9rk43Potentials and displacements for two theoretical seismic sources
https://resolver.caltech.edu/CaltechAUTHORS:20140318-111309690
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1976
DOI: 10.1111/j.1365-246X.1976.tb01265.x
Theoretical, P, SV, and SH displacement potentials and displacements for a double couple or point shear dislocation source and for a 'mixed quadrupole' source at any arbitrary orientation in an isotropic homogeneous elastic space are expressed as multiple integral and derivative operations on the source history in the time domain and their algebraic equivalent in the frequency domain. These sources have the same angle orientation functions, which are given explicitly. The double couple and 'mixed quadrupole' are both quadrupole sources but, unlike the double couple, the P and S waves from a 'mixed quadrupole' have different source histories. Analytic displacements are obtained using as examples the Ohnaka shear dislocation history for a double couple and the Randall and Archambeau tectonic release histories for 'mixed quadrupole' sources.
The displacement fields are investigated numerically, in order to establish a criterion for estimating the minimum range for applying far-field theory results to the total displacement field. The chosen criterion is the ratio of the far-field peak amplitude, which is a function of source rise or duration time, to the static displacement, which is a near-field phenomenon. The proposed criterion is found to be conservative as to the minimum range for the farfield, predicted (1/R) dependence of the total field peak amplitude, but quite satisfactory for time domain estimates of moment and corner frequency based on far-field theory.https://authors.library.caltech.edu/records/tss33-a5519The body waves due to a general seismic source in a layered earth model: 1. Formulation of the theory
https://resolver.caltech.edu/CaltechAUTHORS:20140314-102548196
Authors: {'items': [{'id': 'Bache-T-C', 'name': {'family': 'Bache', 'given': 'T. C.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}]}
Year: 1976
The radiation field exterior to any kind of volume source in a homogeneous medium can be represented in terms of an expansion in spherical harmonics. Such an expansion then provides an equivalent elastic source representation of quite general character in that nearly any proposed seismic source model, whether obtained using analytical or numerical (finite difference or finite element) methods, can be written in this form. The compatibility of this equivalent source with currently used source models, especially numerical models including detailed computations of the nonlinear processes at the source, is discussed. The equivalent source is then embedded in a stack of plane elastic layers representing the near-source crustal geology, and expressions are derived for computing the steeply emergent body waves exiting the base of the model. These displacements can then be combined with transfer functions representing the effect of the remainder of the travel path to compute theoretical seismograms for the body waves recorded in the far-field.https://authors.library.caltech.edu/records/n25hz-31439Elastic relaxation coefficients for a spherical cavity in a
prestressed medium of arbitrary orientation
https://resolver.caltech.edu/CaltechAUTHORS:20140318-113132595
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1977
DOI: 10.1111/j.1365-246X.1977.tb04185.x
Archambeau gave elastic relaxation coefficients for a spherical cavity introduced into a pure shear prestress field. The technique is generalized to a stress field for which only the trace of σ_(ij)^(0) is zero. The coefficients are given for a general deviatoric prestress field of arbitrary orientation. They are then specialized to the case of a pure shear stress expressed in terms of the orientation angles commonly used in fault plane descriptions, i.e. dip and slip angle. The extension of this technique to an arbitrary homogeneous prestress field and its limitations are discussed.https://authors.library.caltech.edu/records/jn3tn-p4g54A note on nonequivalent quadrupole source cylindrical shear potentials which give equal displacements
https://resolver.caltech.edu/CaltechAUTHORS:20140313-153000014
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}, {'id': 'Helmberger-D-V', 'name': {'family': 'Helmberger', 'given': 'D. V.'}}]}
Year: 1978
Two standard integral forms of the cylindrical shear potentials for point quadrupole seismic sources, a frequency domain k-integral and a time domain Cagniardde Hoop path p-integral, are shown not to be the frequency-time domain inverse of each other. Their relationship is derived and they are shown to be seismically equivalent in that they yield the same displacement field.https://authors.library.caltech.edu/records/4844q-9x755Crustal structures inferred from Rayleigh-wave signatures of NTS explosions
https://resolver.caltech.edu/CaltechAUTHORS:20140314-083217668
Authors: {'items': [{'id': 'Bache-T-C', 'name': {'family': 'Bache', 'given': 'Thomas C.'}}, {'id': 'Rodi-W-L', 'name': {'family': 'Rodi', 'given': 'William L.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1978
An improved method for determining plane-layered earth models that accurately represent the important features controlling the amplitude and wave form of surface waves is presented. The method includes a formal inversion of phase and group velocity data determined from observed seismograms and is applied to the Rayleigh waves from Nevada Test Site (NTS) explosions recorded at Albuquerque, New Mexico and Tucson, Arizona. For both paths the observed dispersion agrees with that from the models with a maximum residual of only 0.01 km/sec. Further, the models are consistent with other available information about these paths (e.g., from refraction surveys). To properly account for local differences in the material at the source, an approximate theory is constructed in which the amplitude excitation is computed in a source structure and the dispersion in a separate path structure. Using this theory and the crustal models from the inversion, synthetic seismograms are computed that match the observed seismograms remarkably well.https://authors.library.caltech.edu/records/s82vg-eba77Synthetics and theoretical seismology
https://resolver.caltech.edu/CaltechAUTHORS:20140318-133548441
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1983
DOI: 10.1029/RG021i006p01299
In the near field, discrete-finite wave number schemes are economic since they involve fewer wave numbers than most wave number integration schemes. The number of wave numbers is determined by the range and the location of artificial reflectors or fictitious sources inherent in discrete wave number techniques. The number and spacing of wave numbers in wave number integration schemes are determined by the desired accuracy.
The vertical integration schemes used in the near field have been either spectral (Apsel, 1979, Bouchon, 1981) as in the regional techniques or finite-element (Olson,1982) and finite-difference in the time domain as in the Alexseev-Mikhailenko method. The finite element schemes have the disadvantage in that the vertical step size is determined by the desired maximum frequency content, which in turn determines the time step required for stability. This time step is usually many times smaller than the time increment associated with the maximum frequency.https://authors.library.caltech.edu/records/9jqj1-y4y34A generalized reflection-transmission coefficient matrix and discrete wavenumber method for synthetic seismograms
https://resolver.caltech.edu/CaltechAUTHORS:20140319-120031723
Authors: {'items': [{'id': 'Yao-Z-X', 'name': {'family': 'Yao', 'given': 'Z. X.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}]}
Year: 1983
Expressions for displacements on the surface of a layered half-space due to point force are given in terms of generalized reflection and transmission coefficient matrices (Kennett, 1980) and the discrete wavenumber summation method (Bouchon, 1981). The Bouchon method with complex frequencies yields accurate near-field dynamic and static solutions.
The algorithm is extended to include simultaneous evaluation of multiple sources at different depths. This feature is the same as in Olson's finite element discrete Fourier Bessel code (DWFE) (Olson, 1982).
As numerical examples, we calculate some layered half-space problems. The results agree with synthetics generated with the Cagniard-de Hoop technique, P-SV modes, and DWFE codes. For a 10-layered crust upper mantle model with a bandwidth of 0 to 10 Hz, this technique requires one-tenth the time of the DWFE calculation. In the presence of velocity gradients, where finer layering is required, the DWFE code is more efficient.https://authors.library.caltech.edu/records/wp4dq-8f535Source models and yield-scaling relations for underground nuclear explosions at Amchitka Island
https://resolver.caltech.edu/CaltechAUTHORS:20140313-153952350
Authors: {'items': [{'id': 'Lay-T', 'name': {'family': 'Lay', 'given': 'Thorne'}, 'orcid': '0000-0003-2360-4213'}, {'id': 'Helmberger-D-V', 'name': {'family': 'Helmberger', 'given': 'Don V.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1984
Source models are determined for the three underground nuclear explosions at the Amchitka test site using seismic observations in the period range 0.5 to 20.0 sec. Empirical yield-scaling relations are inferred from the source models and compared with the predictions of the Haskell, Mueller-Murphy, and finite difference numerical models. Several recent studies of high-frequency, near-field signals and teleseismic short-period P waves for LONGSHOT, MILROW, and CANNIKIN constrain the source functions at periods of 0.5 to 2.0 sec. Teleseismic pS and Rayleigh wave observations are used to constrain the source functions at longer periods. Using a modified Haskell source time function representation given by
ψ(t) = ψ_∞ {1-e^(-kt)[1 + Kt + (Kt)^2/2-B(Kt)^3]},
the data are best-fit if the corner frequency parameter, K, scales as predicted by the Mueller-Murphy model, and if the amount of overshoot in the reduced displacement potential, which is proportional to B, decreases with increasing yield (depth of burial). The latter behavior is opposite to that predicted by the Mueller-Murphy model and follows from the observation that the long-period level of the explosion potential, ψ_∝, increases with yield, W, by ψ_∝ ∝ W^(0.90), or with yield and depth by ψ_∝ ∝ W/h^(1/3). This long-period and overshoot scaling is consistent with that found for some numerical models, and allowing for the depth dependence of the Rayleigh wave excitation, results in the observed M_S versus log(W) slope of ∼1. The decrease in overshoot with increasing depth of burial may be the result of the increase in shear strength with increasing overburden pressure. If yield or depth dependence of the source potential overshoot proves to be a general phenomenon, a possibility supported by a preliminary investigation of Pahute Mesa observations, accurate yield estimation will require broadband seismic data. The source function representation adopted is shown to provide an excellent fit to the rise time of very near-in velocity recordings to the rise time with frequencies of 10 Hz and higher.https://authors.library.caltech.edu/records/g0j9r-bj492The early years of computational seismology at Caltech
https://resolver.caltech.edu/CaltechAUTHORS:20150925-155936293
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1988
Early this year I was asked to make some "remarks" at the 100th anniversary of
the Berkeley station as President of the SSA. Not knowing exactly what was
expected, I decided to do some background research on the history of the Berkeley
station as found in papers, letters, and reports to the Bulletin. I found these very
informative and some very entertaining. Even though a lot of the information was
obviously hearsay and written well after the events, I felt that there was a place for
this type of anecdotal "history" in the Bulletin and probably no better place for it
than in the Presidential Address.https://authors.library.caltech.edu/records/y5ya1-gky21Numerical modelling of SH L_g waves in and near continental
margins
https://resolver.caltech.edu/CaltechAUTHORS:20140317-141448325
Authors: {'items': [{'id': 'Regan-J', 'name': {'family': 'Regan', 'given': 'J.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}]}
Year: 1989
DOI: 10.1111/j.1365-246X.1989.tb05517.x
The effect of transition regions between continental and oceanic structures on the propagation of L_g waves from continental sources is examined. In particular, the attenuation due to variations in layer thickness in such transition regions is calculated and explained for a suite of simple models. The measured attenuation, due to the geometry of the transition regions between the oceanic and continental structures within a partially oceanic path with source and receiver in a continental structure, is at most a factor of four for frequencies from 0.01 to 1 Hz. This is inadequate to explain the observed extinction of L_g along such paths. This extinction has previously been attributed to the effects of the transition region geometry. The method used to calculate the results presented in this study is developed and its validity and accuracy are demonstrated. Propagator matrix seismograms are coupled into a Finite Element calculation to produce hybrid teleseismic SH mode sum seismograms. These hybrid synthetics can be determined for paths including any regional transition zone or other heterogeneity that exists as part of a longer, mostly plane-layered, path. Numerical results presented for a suite of transition models show distinct trends in each of the regions through which the wavefield passes. The wavefield passes through a continent-ocean transition region, then a region of oceanic structure, and finally through an ocean-continent transition region. When an L_g wavefront passes through a continent-ocean transition, the amplitude and coda duration of the L_g wave at the surface both increase. At the same time, much of the modal L_g energy previously trapped in the continental crust is able to escape from the lower crust into the subcrustal layers as body waves. The magnitude of both these effects increases as the length of the transition region increases. When the wavefront passes through the region of oceanic structure further energy escapes from the crustal layer, and produces a decrease in L_g amplitude at the surface. The rate of amplitude decrease is maximum near the transition region and decreases with distance from it. When the wavefield passes through the ocean-continent transition region a rapid decrease in the L_g amplitude at the surface of the crust results. The energy previously trapped in the oceanic crustal layer spreads throughout the thickening crustal layer. Some of the body wave phases produced when the wavefield passes through the continent-ocean transition region are incident on the continental crust in the ocean-continent transition region. These waves are predominantly transmitted back into the crust. The other body wave phases reach depths below the depth of the base of the continental crust before reaching the ocean-continent transition and, thus, escape from the system.https://authors.library.caltech.edu/records/9jvx1-n2w61Seismic representation theorem coupling: synthetic SH mode sum seismograms for non-homogeneous paths
https://resolver.caltech.edu/CaltechAUTHORS:20140312-155958586
Authors: {'items': [{'id': 'Regan-J', 'name': {'family': 'Regan', 'given': 'J.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}]}
Year: 1989
DOI: 10.1111/j.1365-246X.1989.tb02280.x
In this paper the methods for representation theorem coupling of finite-element or finite difference calculations and propagator matrix method calculations (Harkrider) are developed.The validity and accuracy of the resulting hybrid method are demonstrated.The resulting hybrid technique can be used to study the propagation of any phase that can be represented in terms of an SH mode sum seismogram, across regional transition zones or other heterogeneities. These heterogeneities may exist in regions which form subsegments of a longer, mostly plane-layered, path. Examples of structures of interest through which such waves can be propagated using these techniques include, regions of crustal thickening or thinning such as continent-ocean transitions or basins, anomalous bodies of any shape located in the path, and sudden transitions from one layered structure to another. Examples of the types of phases that may be propagated through these structures include Love waves, L_g, S_n, and S_a.https://authors.library.caltech.edu/records/y4zb7-1cp66Shear-velocity structure of the crust and upper mantle beneath the Tibetan Plateau and southeastern China
https://resolver.caltech.edu/CaltechAUTHORS:20140317-131844927
Authors: {'items': [{'id': 'Zhao-L-S', 'name': {'family': 'Zhao', 'given': 'Lian-She'}}, {'id': 'Helmberger-D-V', 'name': {'family': 'Helmberger', 'given': 'Donald V.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1991
DOI: 10.1111/j.1365-246X.1991.tb00807.x
This paper addresses the velocity structure of the crust and upper mantle beneath southern China with special emphasis on the Tibet region. Waveform data from 48 earthquakes as recorded on the WWSSN and GDSN are used in this detailed forward modelling study. Constraints on the upper crustal section are derived from modelling local Love waves in the time domain applying the mode-sum modelling technique. Lower crustal constraints are derived by modelling the P_(nl)-wavetrain with the reflectivity method. An average crustal thickness of 70 km is obtained beneath the Tibetan Plateau with a modest increase of velocity with depth. The lithospheric and upper mantle structure is deduced from modelling S and SS triplication waveform data and relative traveltimes by applying a combination of WKBJ and generalized ray methods. S-SS seismograms chosen with bounce-points directly under Tibet allow remote sensing of this inaccessible region. The resulting model is an averaged 1-D model where corrections for lateral variation have been applied. We conclude that the upper mantle structure in the entire region is basically shield-like below 200 km (SNA). However, the velocity of the lithosphere is abnormally slow, roughly 5 per cent beneath Tibet. The model for Tibet derived does not have a distinct lid, and has a positive velocity gradient in the crust, suggesting crustal shortening. A preliminary velocity model for southeastern China is also suggested.https://authors.library.caltech.edu/records/xdxyp-ehz89Wave fields from an off-center explosion in an embedded solid sphere
https://resolver.caltech.edu/CaltechAUTHORS:20140314-103525409
Authors: {'items': [{'id': 'Zhao-L-S', 'name': {'family': 'Zhao', 'given': 'Lian-She'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1992
This study investigates the effects of explosions in asymmetric source regions on the excitation of seismic body waves. We give an analytic formulation for determining the wave fields from an off-center explosion in an embedded solid sphere in an elastic whole-space. As expected, this geometry generates shear as well as compressional body waves. The calculated wave fields show that the degree of shear-wave generation is determined by the asymmetry of the source region. The results are compared with the known analytic solutions of an explosion in an elastic whole-space and at the center of an elastic sphere embedded in the whole-space. The radiation patterns at different periods for different parameters of the media suggest that the asymmetry of the source region has significant effects on shorter period but has only minor effects on long periods. The long-period P-to-S wave maximum amplitude results are in agreement with that for explosions in axisymmetric cavities.https://authors.library.caltech.edu/records/7dyn2-nns55Theoretical Rayleigh and Love Waves from an Explosion in Prestressed Source Regions
https://resolver.caltech.edu/CaltechAUTHORS:20140313-150932006
Authors: {'items': [{'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'D. G.'}}, {'id': 'Stevens-J-L', 'name': {'family': 'Stevens', 'given': 'J. L.'}}, {'id': 'Archambeau-C-B', 'name': {'family': 'Archambeau', 'given': 'C. B.'}}]}
Year: 1994
Expressions and synthetics for Rayleigh and Love waves generated by theoretical tectonic release models are presented. The multipole formulas are given in terms of the strengths and time functions of the source potentials. This form of the Rayleigh and Love wave expressions is convenient for separating the contribution to the Rayleigh wave due to the compressional and shear-wave source radiation and the contribution of the upgoing and downgoing source radiation for both Rayleigh and Love waves. Because of the ease of using different compression and shear-wave source time functions, these formulas are especially suited for sources for which second- and higher-order moment tensors are needed to describe the source, such as the initial value cavity release problem.
A frequently used model of tectonic release is a double couple superimposed on an explosion. Eventually, we will compare synthetics of this and more realistic models in order to determine for what dimensions of the tectonic release model this assumption is valid and whether the Rayleigh wave is most sensitive to the compressional or shear-wave source history. The pure shear cavity release model is a double couple with separate P- and S-wave source histories. The time scales are proportional to the source region's dimension and differ by their respective body-wave velocities. Thus, a convenient way to model the effect of differing shot point velocities and source dimensions is to run a suite of double-couple source history calculations for the P- and SV-wave sources separately and then sum the different combinations.
One of the more interesting results from this analysis is that the well-known effect of vanishing Rayleigh-wave amplitude as a vertical or horizontal dip-slip double-couple model approaches the free surface is due to the destructive interference between the P- and SV-wave generated Rayleigh waves. The individual Rayleigh-wave amplitudes, unlike the SH-generated Love waves, are comparable in size to those from other double-couple orientations. This has important implications to the modeling of Rayleigh waves from shallow dipslip fault models. Also, the P-wave radiation from double-couple sources is a more efficient generator of Rayleigh waves than the associated SV wave or the P wave from explosions. The latter is probably due to the vertical radiation pattern or amplitude variation over the wave front. This effect should be similar to that of the interaction of wave-front curvature with the free surface.https://authors.library.caltech.edu/records/s33zh-tak43Excitation of atmospheric oscillations by volcanic eruptions
https://resolver.caltech.edu/CaltechAUTHORS:20140317-111546477
Authors: {'items': [{'id': 'Kanamori-H', 'name': {'family': 'Kanamori', 'given': 'Hiroo'}, 'orcid': '0000-0001-8219-9428'}, {'id': 'Mori-Jim', 'name': {'family': 'Mori', 'given': 'Jim'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1994
DOI: 10.1029/94JB01475
We investigated the mechanism of atmospheric oscillations with periods of about 300 s which were observed for the 1991 Pinatubo and the 1982 El Chichón eruptions. Two distinct spectral peaks, at T = 270 and 230 s for the Pinatubo eruption and at T = 195 and 266 s for the El Chichón eruptions, have been reported. We found similar oscillations for the 1980 Mount St. Helens and the 1883 Krakatoa eruptions. To explain these observations, we investigated excitation problems for two types of idealized sources, "mass injection" and "energy injection" sources, placed in an isothermal atmosphere. In general, two modes of oscillations, "acoustic" and "gravity" modes, can be excited. For realistic atmospheric parameters, the acoustic and gravity modes have a period of 275 and 304 s, respectively. For a realistic time history of eruption, atmospheric oscillations with an amplitude of 50 to 100 Pa (0.5 to 1 mbar) can be excited by an energy injection source with a total energy of 10^17 J. This result is consistent with the observations and provides a physical basis for interpretation of atmospheric oscillations excited by volcanic eruptions.https://authors.library.caltech.edu/records/6vmg1-pvh32Determining surface-wave magnitudes from regional Nevada Test
Site data
https://resolver.caltech.edu/CaltechAUTHORS:20140312-140654087
Authors: {'items': [{'id': 'Woods-B-B', 'name': {'family': 'Woods', 'given': 'Bradley B.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}]}
Year: 1995
DOI: 10.1111/j.1365-246X.1995.tb01833.x
We re-examine the use of surface-wave magnitudes to determine the yield of underground nuclear explosions and the associated magnitude-yield scaling relationship. We have calculated surface-wave magnitudes for 190 Nevada Test Site (NTS) shots using regional long-period seismograms from a combined super-network of 55 North American stations. Great effort went towards making the data set comprehensive and diverse in terms of yield, source location and shot medium in order to determine the portability of surface-wave magnitude scales. In particular, we examine Pahute Mesa, Rainier Mesa and Yucca Flat explosions detonated above and below the water table, and which range over three orders of magnitude in yield. By observation we find a low-yield measure threshold of approximately one kiloton (kt) for (assumedly) moderately well-coupled explosions recorded at near-regional (<500 km) stations, which have little microseismic noise. In order to utilize regional surface waves (Δ < 15°) for quantifying sources and for discrimination purposes, we have developed related methods for determining time-domain surface-wave magnitudes and scalar moments from regional Rayleigh waves. Employing regional surface-wave data lowers the effective magnitude threshold. One technique employs synthetic seismograms to establish a relationship between the amplitude of the regional Airy phase, or Rayleigh pulse of the Rayleigh wavetrain and an associated surface-wave magnitude, based on conventional M_S determinations, calculated from synthetic seismograms propagated to 40°. The other method uses synthetic seismograms in a similar fashion, but the relationship used is a more straightforward one between scalar moment and peak Rayleigh wave amplitude. Path corrections are readily implemented to both methods. The inclusion of path corrections decreases the M_S variance by a factor of two and affects the absolute scaling relationship by up to a factor of 0.1 magnitude units. This latter effect is attributed to the particular station network used and the Green's functions used to obtain the 40° M_S values. Using a generic structure for the distance travelled past the actual source-receiver path minimizes the difference between magnitudes determined with and without path corrections. The method gives stable M_S values that correlate well with other magnitude scale values over a range of three orders of magnitude in source yield. Our M_S values scale very similarly to more standard teleseismic M_S values from other studies, although the absolute MS values vary by ±M0.5 magnitude units about ours. Such differences are due in part to the choice of MS formula used. For purposes of future user comparisons, we give conversion values to the previous studies. Our most refined M_S values give the relationship M_S = 1.00 x log_10 (yield) +B, where B is dependent upon source region and shot medium. This yield exponent of unity holds for events of all sizes and is in line with M_S-yield scaling relations found by other studies. When events are grouped with respect to source region, significantly better fits to these individual-site linear-regression curves are obtained compared to the fits obtained using a single, all-inclusive- model. This observation implies that shot-site parameters and source structure can significantly affect surface-wave-magnitude measurements. We present these M_S values primarily to augment the extensive historical analysis of explosion data based on surface-wave magnitudes by using regional data to increase the number of events with surface-wave magnitudes. These magnitudes are consistant with the teleseismically determined magnitudes of larger events. We present our preferred surface-wave moment values in a sequel paper.https://authors.library.caltech.edu/records/qj9xk-9dq59Evaluation of Short-Period, Near-Regional M_s Scales for the Nevada Test Site
https://resolver.caltech.edu/CaltechAUTHORS:20150930-135545135
Authors: {'items': [{'id': 'Bonner-J-L', 'name': {'family': 'Bonner', 'given': 'Jessie L.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}, {'id': 'Herrin-E-T', 'name': {'family': 'Herrin', 'given': 'Eugene T.'}}, {'id': 'Shumway-R-H', 'name': {'family': 'Shumway', 'given': 'Robert H.'}}, {'id': 'Russell-S-A', 'name': {'family': 'Russell', 'given': 'Sara A.'}}, {'id': 'Tibuleac-I-M', 'name': {'family': 'Tibuleac', 'given': 'Ileana M.'}}]}
Year: 2003
DOI: 10.1785/0120020240
Surface wave magnitude (M_s) estimation for small events recorded at
near-regional distances will often require a magnitude scale designed for Rayleigh
waves with periods less than 10 sec. We have examined the performance of applying
two previously published M_s scales on 7-sec Rayleigh waves recorded at distances
less than 500 km. First, we modified the Marshall and Basham (1972) M_s scale,
originally defined for periods greater than 10 sec, to estimate surface wave magnitudes
for short-period Rayleigh waves from earthquakes and explosions on or near
the Nevada Test Site. We refer to this modification as ^(M+B) M_s(7), and we have used
short-period, high-quality dispersion curves to determine empirical path corrections
for the 7-sec Rayleigh waves. We have also examined the performance of the Rezapour
and Pearce (1998) formula, developed using theoretical distance corrections
and surface wave observations with periods greater than 10 sec, for 7-sec Rayleigh
waves ^(R+P) (M_S(7)) as recorded from the same dataset. The results demonstrate that both
formulas can be used to estimate M_s for nuclear explosions and earthquakes over a
wider magnitude distribution than is possible using conventional techniques developed
for 20-sec Rayleigh waves. These M_s(7) values scale consistently with other
Ms studies at regional and teleseismic distances with the variance described by a
constant offset; however, the offset for the ^(M+B) M_s(7) estimates is over one magnitude
unit nearer the teleseismic values than the ^(R+P) M_s(7) estimates. Using our technique, it
is possible to employ a near-regional single-station or sparse network to estimate
surface wave magnitudes, thus allowing quantification of the size of both small earthquakes
and explosions. Finally, we used a jackknife technique to determine the false-alarm
rates for the ^(M+B) M_s(7)-m_b discriminant for this region and found that the probability of misclassifying an earthquake as an explosion is 10%, while the probability
of classifying an explosion as an earthquake was determined to be 1.2%. The misclassification
probabilities are slightly higher for the ^(R+P) M_s(7) estimates. Our future
research will be aimed at examining the transportability of these methods.https://authors.library.caltech.edu/records/e24m7-kx556Development of a Time-Domain, Variable-Period Surface-Wave Magnitude Measurement Procedure for Application at Regional and Teleseismic Distances, Part II: Application and M_s-m_b Performance
https://resolver.caltech.edu/CaltechAUTHORS:20150928-151729561
Authors: {'items': [{'id': 'Bonner-J-L', 'name': {'family': 'Bonner', 'given': 'Jessie L.'}}, {'id': 'Russell-D-R', 'name': {'family': 'Russell', 'given': 'David R.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David G.'}}, {'id': 'Reiter-D-T', 'name': {'family': 'Reiter', 'given': 'Delaine T.'}}, {'id': 'Herrmann-R-B', 'name': {'family': 'Herrmann', 'given': 'Robert B.'}}]}
Year: 2006
DOI: 10.1785/0120050056
The Russell surface-wave magnitude formula, developed in Part I of this two-part article, and the M_s(VMAX) measurement technique, discussed in this article, provide a new method for estimating variable-period surface-wave magnitudes at regional and teleseismic distances. The M_s(VMAX) measurement method consists of applying Butterworth bandpass filters to data at center periods between 8 and 25 sec. The filters are designed to help remove the effects of nondispersed Airy phases at regional and teleseismic distances. We search for the maximum amplitude in all of the variable-period bands and then use the Russell formula to calculate a surface-wave magnitude.
In this companion article, we demonstrate the capabilities of the method by using applications to three different datasets. The first application utilizes a dataset that consists of large earthquakes in the Mediterranean region. The results indicate that the M_s(VMAX) technique provides regional and teleseismic surface-wave magnitude estimates that are in general agreement except for a small distance dependence of −0.002 magnitude units per degree. We also find that the M_s(VMAX) estimates are less than 0.1 magnitude unit different than those from other formulas applied at teleseismic distances such as Rezapour and Pearce (1998) and Vanĕk et al. (1962).
In the second and third applications of the method, we demonstrate that measurements of M_s(VMAX) versus m_b provide adequate separation of the explosion and earthquake populations at the Nevada and Lop Nor Test Sites. At the Nevada Test Site, our technique resulted in the misclassification of two earthquakes in the explosion population. We also determined that the new technique reduces the scatter in the magnitude estimates by 25% when compared with our previous studies using a calibrated regional magnitude formula. For the Lop Nor Test Site, we had no misclassified explosions or earthquakes; however, the data were less comprehensive.
A preliminary analysis of Eurasian earthquake and explosion data suggest that similar slopes are obtained for observed M_s(VMAX) versus m_b data with m_b <5. Thus the data are not converging at lower magnitudes. These results suggest that the discrimination of explosions from earthquakes can be achieved at lower magnitudes using the Russell (2006) formula and the M_s(VMAX) measurement technique.https://authors.library.caltech.edu/records/jqys0-dz435The Surface Wave Magnitude for the 9 October 2006 North Korean Nuclear Explosion
https://resolver.caltech.edu/CaltechAUTHORS:20150930-143743779
Authors: {'items': [{'id': 'Bonner-J-L', 'name': {'family': 'Bonner', 'given': 'Jessie'}}, {'id': 'Herrmann-R-B', 'name': {'family': 'Herrmann', 'given': 'Robert B.'}}, {'id': 'Harkrider-D-G', 'name': {'family': 'Harkrider', 'given': 'David'}}, {'id': 'Pasyanos-M', 'name': {'family': 'Pasyanos', 'given': 'Michael'}}]}
Year: 2008
DOI: 10.1785/0120080929
Surface waves were generated by the North Korean nuclear explosion of 9 October 2006 and were recorded at epicentral distances up to 34°, from which we estimated a surface wave magnitude (M_s) of 2.94 with an interstation standard deviation of 0.17 magnitude units. The International Data Center estimated a body-wave magnitude (m_b) of 4.1. This is the only explosion we have analyzed that was not easily screened as an explosion based on the differences between the M_s and m_b estimates. Additionally, this M_s predicts a yield, based on empirical M_s/yield relationships, that is almost an order of magnitude larger than the 0.5–1 kt reported for this explosion. We investigate how emplacement medium effects on surface wave moment and magnitude may have contributed to the yield discrepancy.https://authors.library.caltech.edu/records/yrbhn-wat46