Diffuse deformation and surface faulting distribution from sub-metric image correlation along the 2019 Ridgecrest ruptures (California, USA)

Bulletin of the Seismological Society of America
By: , and 

Links

Abstract

The 2019 Mw 6.4 and 7.1 Ridgecrest, California, earthquake sequence (July 2019) ruptured consecutively a system of high‐angle strike‐slip cross faults (northeast‐ and northwest‐trending) within 34 hr. The complex rupture mechanism was illuminated by seismological and geodetic data, bringing forward the issue of the interdependency of the two fault systems both at depth and at the surface, and of its effect on the final surface displacement pattern. Here, we use high‐resolution (WorldView and Pleiades) optical satellite image correlation to measure the near‐fault horizontal and vertical surface displacement fields at 0.5 m ground resolution for the two earthquakes. We point out significant differences with previous geodetic‐ and geologic‐based measurements, and document the essential role of distributed faulting and diffuse deformation in producing the observed surface displacement patterns. We derive strain fields from the horizontal displacement maps, and highlight the predominant role of rotation and shear strain in the surface rupture process. We discuss the segmentation of the rupture based on the fault geometry and along‐strike slip variations. We also image several northeast‐trending faults with similar orientation to the deeply embedded shear fabric identified in aftershock studies, and show that these cross faults are present all along the rupture, including at a scale <100 m. Finally, we compare our results to kinematic slip inversions, and show that the surface diffuse deformation is primarily associated with areas of shallow slip deficit; however, this diffuse deformation cannot be explained using elastic modeling. We conclude that inelastic processes play an important role in contributing to the total surface deformation associated with the 2019 Ridgecrest sequence.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Diffuse deformation and surface faulting distribution from sub-metric image correlation along the 2019 Ridgecrest ruptures (California, USA)
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120210036
Volume 5
Issue 111
Year Published 2021
Language English
Publisher Seismological Society of America
Contributing office(s) Geologic Hazards Science Center
Description 28 p.
First page 2275
Last page 2302
Country United States
State California
City Ridgecrest
Google Analytic Metrics Metrics page
Additional publication details