Temporal Seismic Velocity Variations: Recovery Following From the 2019 M7.1 Ridgecrest Earthquake

Session: Observations From the 2019 Ridgecrest Earthquake Sequence
Type: Oral
Date: 4/28/2020
Time: 05:00 PM
Room: 115
Description: 

We investigated seismic velocity changes (dv/v) associated with the Ridgecrest earthquake sequence as observed from high-frequency auto-correlations of ambient seismic noise data. Daily auto-correlation functions were computed for each broadband station within the region that experienced strong ground shaking (peak ground acceleration, PGA > 10 % g) over a period of seven months, centered on the Mw 7.1 earthquake. Travel time shifts in the daily auto-correlation functions, relative to the mean auto-correlation, were computed to produce dv/v time series, which inform the evolving material properties of the shallow crust surrounding the Ridgecrest Fault Zone (RFZ). A short-term velocity drop follows the Mw 7.1 earthquake at stations in the vicinity of RFZ, while those greater than 50 km away showed no such drop despite recording peak ground accelerations of up to more 22 % of g. For the stations that recorded reduced seismic velocities, two distinctive behaviors emerged. Near the areas of highest coseismic slip within the RFZ, seismic velocities recovered over about 3 months. In the vicinity of the nearby Garlock fault, where triggered slip manifested, and north of the RFZ seismic velocities recovered within one month. The seismic velocity changes indicate that the rupture of the RFZ altered the physical properties of the shallow crust in response to the strong ground motion of a large magnitude earthquake.

Presenting Author: Joshua D. Boschelli

Authors