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Kinematic slip model of the July 8, 2021 M6.0 Antelope Valley, California, earthquake

Frederick Pollitz·Charles Wicks·William M Hammond
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Abstract

We present a kinematic slip model of the July 8, 2021 Antelope Valley earthquake from a finite-source inversion based on regional seismic waveforms and static offsets from GPS and InSAR. Seismic waveforms are employed at 6s dominant period out to 100 km from the epicenter, and the combined GPS and InSAR datasets cover the near field and far field out to ∼ 100 km and constrain the overall rupture size. The aftershock pattern defines a nearly north-striking, 50◦ east-dipping fault plane. We find a unilateral rupture along this fault plane propagating southward and updip with predominantly normal slip up to ∼ 1.5m. The estimated seismic moment of 8.47 × 10 22 17 Nm is equivalent to Mw 5.92. A finite-source inversion that retains seismic waveforms and GPS static offsets but omits InSAR range changes yields a seismic moment of 1.08 × 10 25 18 Nm (Mw 5.99). Despite vigorous aftershock activity between 10 km and Earth’s surface, coseismic slip is concentrated in the depth interval 7 - 10 km.

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Source-reported bounding extent: 38° to 39° latitude; -120° to -119° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Frederick Pollitz, Charles Wicks, William M Hammond. 2022-01-26. Kinematic slip model of the July 8, 2021 M6.0 Antelope Valley, California, earthquake. https://doi.org/10.1785/0320210043

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