Abstract
Abstract We present a kinematic slip model of the 8 July 2021 Antelope Valley earthquake from a finite-source inversion based on regional seismic waveforms and static offsets from Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR). Seismic waveforms are employed at 6 s 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 ∼1.5 m. The estimated seismic moment of 8.47×1017 N·m 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 1.08×1018 N·m (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.
Highlights
The 8 July 2021 M 6.0 Antelope Valley, California, earthquake is the largest to have struck the northern Walker Lane area since 1994 (Fig. 1)
The slip centroid of the preferred model (Fig. 5a) is within ∼1 km of 38.50° N, −119.50° E and about 9.0 km depth, similar to but ∼1.5 km deeper than the slip centroid obtained in the U.S Geological Survey (USGS) finitefault model
We use a combination of seismic waveforms and static offsets from Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) to constrain kinematic rupture models of the Antelope Valley earthquake
Summary
The 8 July 2021 M 6.0 Antelope Valley, California, earthquake is the largest to have struck the northern Walker Lane area since 1994 (Fig. 1) It occurred along the eastern edge of the Sierra Nevada range in an area of kinematically linked left-stepping dextral strike-slip faults and north-striking normal faults (Wesnousky, 2005; Rood et al, 2011; Wesnousky et al, 2012). The Walker Lane is a tectonic belt of numerous north-northwest-striking subparallel faults that define the western boundary of the Basin and Range province (Wesnousky et al, 2012). These faults generally accommodate both dextral slip and normal slip. The former is exemplified by the 1872 M 7.6 Owens Valley earthquake, whereas the latter is exemplified by paleogeologic investigations (Wesnousky, 2005) and moment tensor solutions (Ichinose, 2003)
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