Browsing by Author "Frazer, L. Neil"

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    Evaluation of Seismometer Arrays for Earthquake Location
    (Indiana Geological Survey, 1986) Lienert, Barry R.; Frazer, L. Neil; Rudman, Albert J.
    Program HYPOERR evaluates the performance of a small network of arbitrary seismic arrays in determining coordinates and times of seismic events. A linearized inversion following the method of Uhrhammer (1980)is performed for a layered velocity structure by determining the eigenvalues and eigenvectors of the partial derivatives of travel time for P and/or S phases with respect to hypocenter position and origin time for each station in the array. A series of covariance matrices is then obtained to evaluate statistical errors for a specified grid of hypocenter locations at any given depth. Contour plots can then be made of the matrix elements by using standard contouring software. Examples are given for ( 1) the case of a hypothetical quadrapartite array and (2) an actual eight-station ocean-bottom seismometer array deployed around the 95.5° W. Galapagos propagating-rift zone.
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    Generation of Synthetic Seismograms for an Acoustic Layer over an Acoustic Half Space
    (Indiana Geological Survey, 1981) Frazer, L. Neil
    The problem of sound propagation in an acoustic layer over an acoustic half space (liquid over liquid) is solved by quadrature based on the generalized Filon method. Synthetic seismograms are computed by program NFAR1 for nearly arbitrary source-receiver distances and ranges of frequency. The user may optionally plot pressure and horizontal or vertical motion at specific distances. Test cases presented in the text demonstrate that the seismograms agree in arrival time and waveform for all anticipated events, such as direct, reflected, and refracted arrivals, including normal modes.