Kinematic finite-source model for the 24 August 2014 South Napa, California, earthquake from joint inversion of seismic, GPS, and InSAR data

Online Material: Movie of wave propagation, GPS coseismic displacements, rupture velocity, waveform comparisons, geologic and 3D seismic structure, and moment rate functions. On 24 August 2014 at 10:20:44.06 UTC, a large earthquake struck the north San Francisco Bay region, approximately 10 km south‐southwest of Napa, California, causing local damage in older wood frame and masonry buildings, road surfaces, sidewalks, and masonry wall structures (Bray et al. , 2014). Using long‐period (50–20 s) three‐component, complete displacement records, the Berkeley Seismological Laboratory (BSL) estimated the scalar seismic moment at 1.32×1018  N·m for a depth of 11 km, corresponding to a moment magnitude of M w 6.0. The strike/dip/rake from the seismic moment tensor solution was 155°/82°/−172°, which is in overall agreement with the trends of structures comprising the West Napa fault system (Fig. 1). Geologic mapping revealed an approximately 14 km long surface rupture with 40–45 cm maximum observed slip on a complex multibranched fault system (Bray et al. , 2014; Earthquake Engineering Research Institute [EERI], 2014; Mike Oskin and Alex Morelan, written comm., 2014). The largest surface offsets were found on a northwest‐striking trend located approximately 1.8 km west of the mapped West Napa fault. Aftershocks are generally located west of the western branch of the surface fault, which had the largest offsets, and indicate a westward dip of the primary fault plane (Fig. 2). Figure 1. Locations of Berkeley Digital Seismic Network (BDSN) stations are shown as labeled squares. Plate Boundary Observatory (PBO) Global Positioning System (GPS) sites are shown as circles, and the positions of Interferometric Synthetic Aperture Radar (InSAR) returns are small gray squares. San Francisco and Napa Valley are indicated by SF and NV. The Berkeley Seismological Laboratory focal mechanism is shown, and the thick line shows the mapped surface trace (EERI, 2014). Figure 2. (a) Coseismic fault‐slip model based on the joint inversion of …

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