Internal structure of the Garlock fault zone from Ridgecrest aftershocks recorded by dense linear seismic arrays

Hongrui Qiu, Benxin Chi, & Yehuda Ben-Zion

Submitted August 9, 2022, SCEC Contribution #11996

We analyze data of the 2019 Ridgecrest aftershock sequence recorded by two dense seismic arrays that cross the Ridgecrest rupture zone (B4) and Garlock fault (A5). Analyses of fault zone head waves and P-wave delay times at array A5 indicate that the Garlock fault separates two distinctive crustal blocks with P waves traveling ~5% faster in the northern block. The across-fault velocity contrast agrees with large-scale tomography models and generates clear P-wave reflections in waveforms recorded by array B4. Kirchhoff migration of P waves reflected by the Garlock fault yields an image of a near-vertical reflector between 2-6 km depth. The P-wave delay times indicate a ~300-m-wide transition zone near the Garlock fault surface trace beneath array A5, offset to the side with faster seismic velocity. The results provide important constraints for improved derivations of earthquake source parameters and simulations of ruptures and ground motion associated with the Garlock fault.

Key Words
Garlock fault; Fault zone imaging; Fault zone head waves; Fault zone reflected waves; Bimaterial interface

Citation
Qiu, H., Chi, B., & Ben-Zion, Y. (2022). Internal structure of the Garlock fault zone from Ridgecrest aftershocks recorded by dense linear seismic arrays. Geophysical Research Letters, (submitted).