Abstract

Waveforms from the 2004 Parkfield earthquake are compared with three earlier events in 1922, 1934, and 1966, all recorded in station dbn, The Netherlands, at 80° epicentral distance. Digitization of analog records and simulation of digital data enabled the correlation of surface waves for all events. Normalized correlation values are greater than 0.8 for the Parkfield events themselves, compared to values less than 0.5 for correlation with other events in the same region, either with a different mechanism at close distances (1983 Coalinga and 2003 San Simeon) or with the same mechanism, but at larger distances along the same fault system (1984 Morgan Hill). We find that waveforms from sources with the same mechanism show the highest correlations. Waveform amplitudes of the Parkfield events are similar within the accuracy of the calibration of the instrumentation.

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