The Community Fault Model (v. 6.1) for Southern California

Andreas Plesch, Scott T. Marshall, & John H. Shaw

In Preparation August 31, 2025, SCEC Contribution #14391

We present a new version of the Statewide California Earthquake Center (SCEC) Community Fault Model (CFM 6.1) for southern California that describes more than 400 active faults that accommodate relative motions across the Pacific-North American plate boundary. CFM 6.1 is a substantially enhanced representation of the southern California fault system, with systematically updated and improved fault surfaces using detailed fault traces from the USGS Quaternary Fault & Fold database, precisely relocated earthquake and machine-learning enabled hypocenter catalogs, and new focal mechanism solutions (Lin et al., 2007; Yang et al., 2012; Hauksson et al., 2012 + updates), among other datasets. Several of the new fault representations, such as for the 2019 Ridgecrest, California (M 6.4 and M 7.1) events, were developed using an objective, constraint-based interpolation method (Riesner et al., 2017). This resulted in reproducible fault representations that are more precise and often more segmented and interconnected than in previous model versions. The CFM 6.1 was peer reviewed and includes preferred representations for each fault system along with alternative fault representations where significant differences in subsurface structure have been proposed. Based on the fault-to-earthquake association method of Evans et al. (2020), the fault representations in CFM 6.1 show a 5.8% increased association with regional seismicity compared to CFM 5.2, with 89.7% of M 3 and larger events most likely associated with a CFM 6.1 fault. The faults also show a much higher degree of interconnectivity than in previous model versions, which will have implications for the assessment of potential earthquake ruptures involving multiple, distinct faults. The model is distributed and documented through a new website with map and 3D viewer interfaces to facilitate broad usage with a wide range of applications in seismology, tectonic geodesy, computational modeling, and probabilistic and deterministic seismic hazard assessment.

Citation
Plesch, A., Marshall, S. T., & Shaw, J. H. (2025). The Community Fault Model (v. 6.1) for Southern California. Seismological Research Letters, (in preparation).

Related Projects & Working Groups
Community Models, Community Models, CEM, Community Fault Model, CFM