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Regional Seismic Velocity Changes Following the 2019 Mw7.1 Ridgecrest California Earthquake From Autocorrelations and Ps Converted Waves

Session: Advances in Seismic Interferometry: Theory, Computation and Applications

Type: Oral

Date: 4/22/2021

Presentation Time: 05:30 PM Pacific

Description: 

We examine regional transient changes of seismic velocities generated by the Mw7.1 2019 Ridgecrest earthquake in California, using autocorrelations of moving time windows in continuous waveforms recorded at regional stations. We focus on travel time differences in prominent phases generated by an interface around 2 km depth, associated with transmitted Pp waves and converted Ps waves from the ongoing microseismicity. Synthetic tests demonstrate the feasibility of the method for monitoring seismic velocity changes. Taking advantage of the numerous aftershocks in the early period following the occurrence of mainshock, we obtain high temporal resolution of velocity changes up to 20 min following the mainshock. The results reveal regional coseismic velocity drops in the top 1-3 km with an average value of ~2 percent over distances up to 100 km from the Ridgecrest event. The velocity drops are likely dominated by changes in the top crust and are followed by rapid recoveries on timescales of days. In the nearby Coso geothermal region, the observed coseismic velocity drops are up to ~8 percent. The method allows monitoring temporal changes of seismic velocities with high temporal resolution, quick computation and precise spatial mapping of changes. The results suggest that temporal changes of seismic velocities at the subsurface are commonly generated on a regional scale by large events.

Presenting Author: Yang Lu

Student Presenter: No

Authors