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Temporal Seismic Velocity Variations: Recovery Following From the 2019 Mw 7.1 Ridgecrest Earthquake

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

Type: Oral

Date: 4/22/2021

Presentation Time: 05:15 PM Pacific

Description: 

We investigated seismic velocity changes (dv/v) associated with the 2019 Ridgecrest earthquake sequence with high-frequency auto-correlations of ambient seismic noise data. Daily auto-correlation functions were computed for the entirety of 2019 and the first quarter of 2020 for broadband stations within the region, including the temporary broadband stations installed during the aftershock deployment. Travel time shifts in the daily auto-correlation functions, relative to the mean auto-correlation waveform, were computed to produce dv/v time series, which are sensitive to the evolving material properties of the shallow crust surrounding the Ridgecrest fault zone (RFZ). A short-term velocity drop follows the M_w 7.1 earthquake at stations in the vicinity of the M_w 7.1 earthquake, while those greater than 50 km away showed no such drop. Additionally, the maximum, absolute seismic velocity changes are proportional to the logarithm of distance from the fault rupture; the seismic velocity changes exhibit a weak correlation with peak horizontal ground accelerations. Near the areas of the highest coseismic slip within the RFZ, seismic velocities recovered over 3 months. However, in the vicinity of the nearby Garlock fault, where triggered slip manifested, and north of the RFZ, seismic velocities recovered within a month. We interpret the seismic velocity changes and their recovery to be largely due to changes in the physical properties of the shallow crust, such as fault zone damage recovery caused by the earthquake rupture process, and perhaps in response to the large dynamic stresses of passing seismic waves from the earthquake.

Presenting Author: Joshua D. Boschelli

Student Presenter: Yes

Authors