Seismic Imaging of the Mw 7.1 Ridgecrest Earthquake Rupture Zone From Data Recorded by Dense Linear Arrays

Abstract

in the southern part of the Walker Lane shear zone (Figure 1) were felt throughout southern California and produced a vigorous aftershock sequence. These events led to rapid deployments of seismic arrays across and around the Ridgecrest earthquake sequence (Catchings et al., 2020). Kinematic rupture processes of the Mw 6.4 and Mw 7.1 events, surface deformation, and properties of the aftershocks show complex patterns, with strong variations both along strike of the rupture zones and in depth (e.g.,

General Seismic Architecture of the Southern San Andreas Fault Zone around the Thousand Palms Oasis from a Large-N Nodal Array

“…Next, we inspected the delay-time results from all teleseismic and regional events to help quantify the general P-wave velocity (V P ) variations across the profile. For each event, the picked arrival times were corrected for array geometry by subtracting the predicted travel times to individual stations using the TauP algorithm (Crotwell et al, 1999) and the IASP91 global velocity model (e.g., Share, Allam, et al, 2019;Qin et al, 2021;Qiu et al, 2021). A correction was then made for elevation above sea level by subtracting the excess travel times to elevated stations calculated with a reference near-surface V P 2 km=s (from Ajala et al, 2019).…”

“…Assuming this high V P =V S structure extends to a depth of 4 km implies a V P =V S > 2:15, which is the average V P =V S in the uppermost 4 km of the local crust in the Share, Guo, et al (2019) models. A depth of 4 km is approximately the extent of damage-related high electrical conductivities in the area (Share et al, 2021) and fault zone damage along other major faults (e.g., Qin et al, 2021;Qiu et al, 2021).…”

“…3) are consistent with a mature fault system impacted by multiple large seismic events (e.g., Mitchell and Faulkner, 2009), resulting in pervasive off-fault damage. Additional details on the seismic structure of the SSAF in the study area can be obtained by analyzing fault zone head and trapped waves (e.g., Qin et al, 2021;Qiu et al, 2021), reverse-time migration of fault-reflected phases, and migration of the scattered wavefield (Touma et al, 2021). Analyses of such signals are the subject of continuing research.…”

“…Active source seismic exploration and potential field results indicate similar near-surface geometries for the surrounding SSAF (e.g., Catchings et al, 2009;Fuis et al, 2017). To understand these and other features better, we apply a range of tools well-suited for imaging internal fault zone features (e.g., Ben-Zion et al, 2015;Share, Allam, et al, 2019;Qin et al, 2021;Qiu et al, 2021). In this article, we focus on general aspects of the recorded data such as the arrival time, frequency, amplitude, and phase variations across the array from direct, reflected, and transmitted seismic phases.…”

Isotropic Source Components of Events in the 2019 Ridgecrest, California, Earthquake Sequence

“…The M w 6.4 and M w 7.1 earthquakes exhibited lower-than-average rupture speeds (Liu et al, 2019). The earthquake sequence had abundant aftershocks (Ross et al, 2019;Shelly, 2020) that occurred in broad zones with complex geometries and rock damage (Chen et al, 2020;Jia et al, 2020;Qiu et al, 2021;Xu et al, 2020). The Ridgecrest sequence occupied a complex fault network with many previously unmapped faults, suggesting that many events in the sequence may generate damage-related radiation.…”