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Time domain determination of earthquake fault parameters from short-period P-waves Somerville, Paul Graham

Abstract

Source parameters of two shallow earthquakes have been determined by the time-domain analysis of short-period teleseismic recordings. For each event, the effect of the receiver crust was deconvolved from a set of globally distributed recordings using the homomorphic method. The resulting seismograins were compared with the form of the elastic wave radiation computed from Savage's model of radially spreading rupture on a plane elliptical fault surface. This time-domain approach has permitted the determination of several kinematic parameters pertaining to the dynamics of rupture that are not ordinarily evaluated from spectral analysis. These parameters are rupture velocity, the direction of furthest rupture propagation, and the duration of a ramp dislocation time function which was prescribed to be the same everywhere on the fault surface. A general linear inverse scheme has been applied to investigate how well and in what manner the parameters of the source model are determined by the observations. This analysis yields best fitting models, the range of acceptable parameter values, and the distribution of information concerning specific parameters that is contained in specific observations. A consistent discrepancy between the observed and model seismograms during the first half-cycle of motion is attributed to the incorrect prescription of the dislocation time function. It is suggested that a space-dependent function determined theoretically by Kostrov in 1964 would tend to remove this discrepancy.

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