Poster #065, Seismology

Variations of earthquake properties before, during and after the 2019 M7.1 Ridgecrest, CA, earthquake

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Poster Presentation

2020 SCEC Annual Meeting, Poster #065, SCEC Contribution #10198
We attempt to clarify processes associated with the 2019 Ridgecrest earthquake sequence by analyzing space-time variations of seismicity, potency values and focal mechanisms of earthquakes leading to and during the sequence. Over the 20 years before the Mw7.1 mainshock, the percentage of normal faulting events decreased gradually from 25% to below 10%, indicating a long-term increase of shear stress. The Mw6.4 and Mw7.1 earthquakes terminated in areas with strong geological changes likely producing geometrical fault complexities that arrested the ruptures. The aftershocks are characterized by highly diverse focal mechanisms and produced volumetric brittle deformation concentrated in a 5-10 km wide zone around the main ruptures. Early aftershocks of the Mw7.1 event extended over a wide area below typical seismogenic depth, consistent with a transient deepening of the brittle-ductile transition. The Ridgecrest earthquake sequence produced considerable rock damage in the surrounding crust, including below the nominal seismogenic zone.