Untangling the dynamics of the 2019 Ridgecrest sequence by integrated dynamic rupture and Coulomb stress modeling across an immature 3D conjugate fault network

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

doi:10.5194/egusphere-egu2020-15268

Abstract

&lt;p&gt;We present combined 3D dynamic rupture scenarios of the 2019 M&lt;sub&gt;w&lt;/sub&gt;6.4 Searles Valley and M&lt;sub&gt;w&lt;/sub&gt;7.1 Ridgecrest earthquakes closely constrained by observations, incorporating complex subsurface material properties, high-resolution topography and off-fault plastic deformation empowered by supercomputing.&amp;#160;A detailed 3D non-vertical fault model of the active quasi-orthogonal intersecting fault network is built by integrating relocated aftershocks and surface ruptures constrained by space geodesy and field observations. All faults are exposed to a 3D SCEC community stress model as well as long- and short-term static and dynamic stress transfers, which impact rupture dynamics, particularly in the vicinity of complexities in fault geometry.&lt;/p&gt;&lt;p&gt;By assuming apparently weak faults due to the effect of rapid velocity-weakening friction and elevated fluid pressure, we determine initial stresses and fault strength. Multi-fault rupture directivity and velocity of both events are constrained by aftershock calibrated back-projection.&amp;#160;In the presented scenario two conjugate faults simultaneously rupture in the M&lt;sub&gt;w&lt;/sub&gt;6.4 event, while only the SW-segment breaks the surface. The M&lt;sub&gt;w&lt;/sub&gt;7.1 event experiences the full final state of stress (dynamic plus static effects) of the Searles Valley scenario, leading to complex rupture including re-activation of the conjugate M&lt;sub&gt;w&lt;/sub&gt;6.4 segment, mixed crack and pulse-like propagation, tunneling beneath the fault intersection and choosing one Southern branch only. Both events exhibit a high dynamic stress drop reflecting the immature fault system. The foreshock induces a considerable Coulomb stress change in the M&lt;sub&gt;w&lt;/sub&gt;7.1 hypocentral region; however, not enough to trigger rupture across the stress-shadowed main fault. Both scenarios match key observations including magnitude, rupture speed, directivity, off-fault damage, slip distribution from kinematic inversion, teleseismic waveforms, GPS, and InSAR ground deformation; while shedding light on geometric, strength and stress factors governing the complex rupture evolution and interaction of the Ridgecrest sequence.&lt;/p&gt;

Full Text