Abstract
The variation of stress on faults is important for our understanding of fault friction and the dynamics of earthquake ruptures. However, we still have little observational constraints on their absolute magnitude, or their variations in space and in time over the seismic cycle. Here we use a new geodetic imaging technique to measure the 3D coseismic slip vectors along the 2019 Ridgecrest surface ruptures and invert them for the coseismic stress state. We find that the coseismic stresses show an eastward rotation that becomes increasingly transtensional from south-to-north along the rupture, that matches the known background stress state. We find that the main fault near the M w 7.1 mainshock hypocenter was critically stressed. Coseismic slip was maximum there and decreased gradually along strike as the fault became less optimally oriented due its curved geometry. The variations of slip and stress along the curved faults are used to infer the static and dynamic fault friction assuming Mohr-Coulomb failure. We find shear stresses of 4–9 MPa in the shallow crust (∼1.3 km depth) and that fault friction drops from a static, Byerlee-type, value of 0.61 (Formula presented.) 0.14 to a dynamic value of 0.29 (Formula presented.) 0.04 during seismic slip. These values explain quantitatively the slip variations along a transpressional fault bend.
| Original language | English |
|---|---|
| Article number | e2022JB024519 |
| Pages (from-to) | 1-20 |
| Number of pages | 20 |
| Journal | Journal of Geophysical Research: Solid Earth |
| Volume | 127 |
| Issue number | 11 |
| Early online date | 28 Oct 2022 |
| DOIs | |
| Publication status | Published (in print/issue) - 1 Nov 2022 |
Bibliographical note
Funding Information:We thank Jeanne Hardebeck, Xin Wang, Egill Hauksson and Shuzhong Sheng for making their stress results available. We thank Kim Olson, the editor Isabelle Manighetti, the associate editor and two anonymous reviewers for their comments and suggestions which helped strengthen the manuscript. We thank the NASA NGA commercial archive data service for access to the WorldView imagery ( https://cad4nasa.gsfc.nasa.gov/index.php ) which is provided under the NextView license agreement. This research was supported by the NASA Earth Surface and Interior focus area and performed at the Jet Propulsion Laboratory, California Institute of Technology (80NM0018D0004). Satellite imagery for this project were also purchased under SCEC Grant 19222.
Publisher Copyright:
© 2022. American Geophysical Union. All Rights Reserved.
Keywords
- friction
- geodesy
- Ridgecrest
- stress
