abstract

The digital data base provided by the SRO and ASRO stations is exploited in a detailed body-wave analysis of the rupture process of two deep earthquakes. The data are processed by simultaneously deconvolving the long- and short-period channels to produce broadband records of body-wave ground displacement and velocity. These pulse shapes show significant complexity and directivity with frequency content up to 5 Hz. To model these waveforms theoretical seismograms are generated by using the full wave theory to simulate the effects of propagation in the Earth, and by using dynamically realistic source models, where the source complexity is modeled as a sequence of simple subevents. In order to model the high-frequency content of the body waves, the AFL Q model is used, as Q models derived from long-period data are inadequate. By combining the relative locations of the subevents with the inferred rupture areas, we determine complete rupture histories for the events, including estimates of the dynamic and static stress drops (between 40 and 60 bars), the rupture velocity, and the rupture geometry. The results of this modeling are interpreted in terms of the barrier model proposed by Das and Aki in which the rupture complexity is controlled by the distribution of fracture strength.

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