Coseismic Shallow Slip Deficit Accounted for by Diffuse Off-Fault Deformation

Creators: Antoine, Solène L.^{1, 2, 3}; Klinger, Yann^{1, 2}; Wang, Kang^{4, 5}; Bürgmann, Roland⁴

1. University of Paris
2. Institut de Physique du Globe de Paris
3. California Institute of Technology
4. University of California, Berkeley
5. Now at EarthScope Consortium Inc., Socorro, NM, USA

Abstract

Earthquake ruptures produce fault slip and kilometer‐wide diffuse deformation of the host rocks. However, the origin of the diffuse deformation and its role in the rupture process are debated. We produce a refined slip model for the 2019 Ridgecrest, California, earthquakes, and analyze the relations between down‐dip rupture process, and surface diffuse deformation. We show that the decrease in coseismic slip toward the ground surface, also known as shallow slip deficit (SSD), correlates with the occurrence of diffuse deformation at the surface, which is not accounted for by models assuming elastic host rocks. Hence, we suggest that a significant part of the SSD in earthquake source models could be interpreted as a proxy for shallow diffuse inelastic deformation around faults. Revisiting earthquake source models for 28 continental earthquakes, we discuss the controlling parameters of the SSD and diffuse deformation, and propose a conceptual model of the near‐field coseismic surface deformation.

Copyright and License

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Acknowledgement

This work was partly supported by TOSCA CNES and the ANR-18-CE31-0012 projects. Yann Klinger was supported by the Miller Foundation at UC Berkeley during his visit at UC Berkeley. Roland Bürgmann and Kang Wang acknowledge support by the Southern California Earthquake Center (SCEC). This study contributed to the IdEx Université de Paris ANR-18-IDEX-0001.

Data Availability

Static Global Navigation Satellite System (GNSS) coseismic displacements are available at http://sopac-csrc.ucsd.edu/index.php/ridgecrestjuly2019 (last accessed June 2024). InSAR coseismic displacement data used in this study are available at K. Wang and Burgmann (2019) (last accessed June 2024; see also K. Wang & Bürgmann, 2020). High-resolution optical displacement maps are available at Antoine et al., 2024b (last accessed June 2024; see also Antoine et al., 2021). Fault offsets extracted from high-resolution optical image correlation results, and slip model derived are available at Antoine et al., 2024c (last accessed June 2024).

Supplemental Material

Supporting information (PDF).

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Geophysical Research Letters - 2024 - Antoine - Coseismic Shallow Slip Deficit Accounted for by Diffuse Off‐Fault.pdf

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