Depth-dependence of post-seismic velocity changes in and near source area of the 2013 M7.0 Lushan earthquake revealed by S coda of repeating events

Abstract

I investigated postseismic velocity changes within focal area of the 2013 M7.0 Lushan earthquake using coda-wave data of repeating small earthquakes. I employed template matching and grid search methods to identify well-defined repeating earthquakes in order to minimize artifacts induced by variations in source location. I identified a total of 3 isolated patches in a two-month period after the M7.0 mainshock. I applied the coda wave interferometry technique to the waveform data of the identified repeating earthquakes to estimate velocity changes between the first and subsequent events in each cluster. Up to 0.1–0.2% velocity increase is observed from the S coda of repeating events occurred at regions surrounding the large coseismic slip area at seismogenic depths. My observations suggest that a large percent of velocity changes may occur at surface near the stations or shallow, however, healing along the propagation paths in the deep (~5–20km) is likely have contributed to the amount of velocity changes observed after the Lushan earthquake.