Reconciling shallow and deep fault slip associated with the July 2019 Ridgecrest earthquake sequence
Abstract
How deep and shallow fault slip are related is a question that has attracted much recent attention, in part because of the increase in resolution of shallow fault slip from a new generation of near-field geodetic data. The question is pertinent both to our general understanding of earthquake physics as well as the displacement and deformation hazards associated with surface rupturing earthquakes. The July 2019 M6.4 and M7.1 Ridgecrest earthquake sequence represents an exceptional opportunity to analyze how deep and shallow fault slip processes and surface deformation are related. The sequences produced predominantly left-lateral and right-lateral surface rupture of up to ~4.5 meters along ~20km and ~50km stretches, trending NE-SW and NW-SE, respectively. Surface displacement was concentrated on principal rupture planes but significant accompanying distributed deformation on discrete sub-parallel faults and shear zones occurred in zones as wide as 4 kilometers. Both ruptures terminate with complicated faulting patterns comprising multiple strands oriented sub-parallel or oblique to the principal ruptures. We combine far-field geodesy (GNSS and INSAR) and seismic data, with near-field optical image cross-correlation and high-resolution LIDAR (both truck-mounted and airborne) and field hand measurements. We invert the surface displacement field for sub-surface slip distribution and relate variations in estimated fault zone width to variations in vertical shallow fault slip gradients and the degree of discrete, distributed deformation on different fault strands. Additionally, we use independent constraints on the depth of the China Lake basin and bedrock geology to assess the mechanical controls on the nature of surface deformation associated with the rupture.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S43C..02B
- Keywords:
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- 7299 General or miscellaneous;
- SEISMOLOGY