Justin L. Rubinstein and Gregory C. Beroza
Friday 310pm -- Session S53D
Previous studies [Rubinstein and Beroza, 2004 (a,b); Schaff and Beroza, 2004] have shown that the strong shaking resultant from medium and large earthquakes can result in the formation and/or growth of microcracks in the near surface, resulting in reduced seismic velocities at distances exceeding 30km. We use moving window cross correlation on the waveforms of repeating earthquake sequences in the Parkfield area to identify temporal changes in wave propagation coincident with the earthquake, evidence of the damage that the Parkfield earthquake caused. The largest delays we observe are in the S coda, and exceed 10ms. Parkfield provides a unique opportunity where we can better understand to what depth damage caused by strong ground motion (nonlinear strong ground motion) occurs as there are many downhole and uphole seismometers in the region.
The results are detailed here