[
    {
        "id": "authors:b4sdc-mah64",
        "collection": "authors",
        "collection_id": "b4sdc-mah64",
        "cite_using_url": "https://resolver.caltech.edu/CaltechEERL:1971.EERL-71-05",
        "type": "monograph",
        "title": "High frequency errors and instrument corrections of strong-motion accelerograms",
        "author": [
            {
                "family_name": "Trifunac",
                "given_name": "Mihailo D.",
                "clpid": "Trifunac-M-D"
            },
            {
                "family_name": "Udwadia",
                "given_name": "F. E.",
                "clpid": "Udwadia-F-E"
            },
            {
                "family_name": "Brady",
                "given_name": "Arthur Gerald",
                "clpid": "Brady-A-G"
            }
        ],
        "abstract": "A study of high-frequency errors present in digitized accelerograms and an analysis of the distribution of unequally spaced, hand-digitized data indicates that the Fourier content of digitized accelerogram. data may be accurate up to about 25 cps.\n\nTwo methods for accelerometer instrument correction are described: (1) a direct numerical differentiation of recorded accelerograms from which high-frequency digitization errors have been filtered out and (2) an ideal \"mathematical accelerometer\" with a natural frequency significantly higher than the natural frequency of the recording instrument. Although both methods give good results, the first one is recommended for the standard use.",
        "publisher": "California Institute of Technology",
        "publication_date": "1971-01-01"
    },
    {
        "id": "authors:m7q42-cmy68",
        "collection": "authors",
        "collection_id": "m7q42-cmy68",
        "cite_using_url": "https://resolver.caltech.edu/CaltechEERL:1966.EERL.1966.001",
        "type": "monograph",
        "title": "Studies of response to earthquake ground motion",
        "author": [
            {
                "family_name": "Brady",
                "given_name": "Arthur Gerald",
                "clpid": "Brady-A-G"
            }
        ],
        "abstract": "A study is made of the accuracy of electronic digital computer calculations of ground displacement and response spectra from strong-motion earthquake accelerograms. This involves an investigation of methods of the preparatory reduction of accelerograms into a form useful for the digital computations and of the accuracy of subsequent digital calculations. Various checks are made for both the ground displacement and response spectra results, and it is concluded that the main errors are those involved in digitizing the original record. Differences resulting from various investigators digitizing the same experimental record may become as large as 100% of the maximum computed ground displacements. The spread of the results of ground displacement calculations is greater than that of the response spectra calculations. Standardized methods of adjustment and calculation are recommended, to minimize such errors.\nStudies are made of the spread of response spectral values about their mean. The distribution is investigated experimentally by Monte Carlo techniques using an electric analog system with white noise excitation, and histograms are presented indicating the dependence of the distribution on the damping and period of the structure. Approximate distributions are obtained analytically by confirming and extending existing results with accurate digital computer calculations. A comparison of the experimental and  analytical approaches indicates good agreement for low damping values where the approximations are valid. A family of distribution curves to be used in conjunction with existing average spectra is presented. The combination of analog and digital computations used with Monte Carlo techniques is a promising approach to the statistical problems of earthquake engineering.\nMethods of analysis of very small earthquake ground motion records obtained simultaneously at different sites are discussed. The advantages of Fourier spectrum analysis for certain types of studies and methods of calculation of Fourier spectra are presented. The digitizing and analysis of several earthquake records is described and checks are made of the dependence of results on digitizing procedure, earthquake duration and integration step length. Possible dangers of a direct ratio comparison of Fourier spectra curves are pointed out and the necessity for some type of smoothing procedure before comparison is established. A standard method of analysis for the study of comparative ground motion at different sites is recommended.",
        "publisher": "California Institute of Technology",
        "publication_date": "1966-01-01"
    }
]