The 1981 – 2022 Southern California Seismic Network Waveform Relocated and Focal Mechanisms Catalogs: New Seismological and Tectonic Insights

Egill Hauksson, & Peter M. Shearer

Published September 11, 2022, SCEC Contribution #12480, 2022 SCEC Annual Meeting Poster #057

We have refined and updated the catalogs of earthquake hypocenters (Hauksson et al., 2012) and focal mechanisms (Yang et al., 2012) for southern California. The SCSN waveform relocated catalog that consists of 40 years of ~800,000 relocated earthquakes, includes aftershock sequences from four (M>7) mainshocks, 1992 Landers, 1999 Hector Mine, 2010 El Mayor-Cucapah, and 2019 Ridgecrest. This seismicity forms complex spatial and temporal patterns related to Pacific North America plate boundary tectonics processes. All of the M>7 mainshocks occurred outside the San Andreas Fault zone proper, and image the width of the plate boundary crustal deformation zone. In general, the smaller magnitude background seismicity occurs across the same region of low stress, elevated strain rate and heat flow.

The 40 year catalog of first motion and S/P-ratio amplitudes focal mechanisms contains more than ~165,000 events. The focal mechanisms map regions of predominantly strike-slip faulting along the San Andreas Fault system. Limited regions of dip-slip or normal or reverse faulting are also identified, mostly related to geometrical complexities of the plate boundary. The stress field determined from the focal mechanism catalog is similar to the regional GNSS strain field but provides additional near fault spatial resolution of stress field variations.

Previously these catalogs have been used for numerous studies such as: a) monitoring of temporal and spatial evolution of seismicity (Hauksson et al., 2022), b) mapping of the geophysical properties of fault zones (Yang et al., 2022), c) 3D velocity model inversions (Tape et al., 2009), d) stress drop determinations, (Shearer et al, 2022), e) rheological properties of the crust, (Hauksson and Meier, 2018), f) identification of repeater earthquake sequences, (Hauksson et al, in prep. ), g) earthquake statistics, Zaliapin and Ben-Zion (2021), h) identification and monitoring of anthropogenic seismicity.( Chen et al, 2012), i) aftershock studies; van der Elst and Shaw (2015), and j) stress field determination (Yang and Hauksson, 2013). You can access the newest versions of these catalogs here: https://scedc.caltech.edu/eq-catalogs/altcatalogs.html

Key Words
Seismicity, seismotectonics, rheology, stress, strength

Citation
Hauksson, E., & Shearer, P. M. (2022, 09). The 1981 – 2022 Southern California Seismic Network Waveform Relocated and Focal Mechanisms Catalogs: New Seismological and Tectonic Insights. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology