Surface Slip Distribution for the 2019 M7.1 Ridgecrest, California Earthquake Rupture

Session: Observations From the 2019 Ridgecrest Earthquake Sequence [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Surface rupture in the July 5, 2019 Mw 7.1 Ridgecrest, California earthquake occurred along a distributed, ~50-km-long and northwest-trending fault zone north of the Garlock fault and south of the Coso volcanic field. Here, we synthesize field observation of lateral and vertical surface slip associated with the Mw 7.1 rupture made by the Ridgecrest Rupture Mapping Group (Ponti et al., in review––SRL). We present >500 unique displacement observations, including >230 right-lateral, >50 left-lateral and >220 vertical (normal-faulting) measurements. We compute moving-mean and moving-maximum displacement curves for 11 separate subparallel fault strands and sum these results to yield cumulate right- and left-lateral slip distributions. We also difference west(dominant)- and east-facing vertical displacement curves to yield cumulative vertical displacement along strike. Our analyses resolved a northwest-trending, right-lateral slip profile with a prominent zone of large, ~3–5-m slip that spans ~15-km of along-strike fault length near the center of the rupture. Peak right-lateral displacement is ~4.4 m using the summed moving-mean curves and as much as ~7 m using the moving-maximum curves. North and south of this peak slip zone, right-lateral displacements are generally less than ~0.5 and 1.0 m, respectively. Left-lateral displacements are mostly restricted to the northwestern ~20 km of the rupture and are <0.2 m. Cumulative, down-to-the-west vertical displacement reaches a maximum of ~2.5 m near the Mw 7.1 epicenter but is <0.8 m elsewhere along the rupture. We discuss our results within the framework of local bedrock structure inferred from relocated aftershocks and seismic reflection data, as well as surface-slip distributions for previous ruptures of the eastern California shear zone. We also compare our field observations to slip estimates derived from remote-sensing (e.g., pixel-tracking) results from 0.5-m-resolution satellite data.

Presenting Author: Christopher B. DuRoss

Authors