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Observationally constrained multi-scale dynamic rupture modeling of the 2019 Ridgecrest earthquakes

Taufiq Taufiqurrahman, Alice-Agnes Gabriel, Duo Li, Thomas Ulrich, Sara Aniko Wirp, Sara Carena, Alessandro Verdecchia, & Frantisek Gallovic

Published August 16, 2020, SCEC Contribution #10773, 2020 SCEC Annual Meeting Poster #157

We present observationally and Coulomb stress modeling constrained 3D dynamic rupture scenarios combining the 2019 Mw6.4 Searles Valley and Mw7.1 Ridgecrest earthquakes, complemented by aftershock calibrated back-projection (Li & Ghosh, 2016) and kinematic parametric source inversion (PSI, Hallo and Gallovič, 2020). A detailed 3D non-vertical fault model of the quasi orthogonal intersecting fault network is built from relocated aftershocks and surface ruptures constrained by space geodesy and field observations. All faults are embedded in modeled cumulative (coseismic plus postseismic) Coulomb stresses (∆CFS), heterogeneous 3D SCEC community models of tectonic stresses, and subsurface materials. The faults intersect high-resolution topography and may cause off-fault plastic deformation during frictional failure. By assuming faults under rate-and-state (strong velocity weakening) friction and elevated fluid pressure, we determine initial stresses and fault strength. We validate a unified multi-scale scenario of both events with key observations including fault surface offsets, GPS and InSAR surface deformation, moment rate release, slip distribution, teleseismic, and strong ground motion waveforms. The dynamic model ruptures two conjugate faults simultaneously in the Mw6.4 event whereas only the SW-segment breaks the surface. The Mw7.1 dynamic rupture scenario includes the full state of stress: 3D tectonic loading, ∆CFS, and the dynamic and static stresses transferred by the Searles Valley scenario. We model complex rupture evolution including re-activation of the conjugate Mw6.4 segment, mixed crack- and pulse-like propagation, and delayed tunneling beneath the fault intersection. We quantify the considerable dynamic and static stress changes the Mw6.4 dynamic rupture model induces in the Mw7.1 hypocentral region, which is not enough to trigger rupture across the stress-shadowed main fault. A systematic mismatch in rupture speed and an azimuth dependent time delay of synthetic waveforms implies the need for better constrained near-fault zone properties. Advances in high-performance computing and dense observations allow us to routinely combine and cross-verify observational constraints, specifically community models, with physics-based modeling to provide mechanically viable insight into rupture on complex fault systems.

Key Words
Ridgecrest earthquakes, complex fault systems, dynamic rupture, Coulomb stresses, off-fault plastic deformation

Taufiqurrahman, T., Gabriel, A., Li, D., Ulrich, T., Wirp, S., Carena, S., Verdecchia, A., & Gallovic, F. (2020, 08). Observationally constrained multi-scale dynamic rupture modeling of the 2019 Ridgecrest earthquakes. Poster Presentation at 2020 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)