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Evaluation of the Statewide Community Fault Model (SCFM) Version 3.0 and Continued Updates to the SCEC CFM 5.0

Andreas Plesch, John H. Shaw, Craig Nicholson, Christopher C. Sorlien, & . SCFM 2015 workshop participants

Published 2015, SCEC Contribution #6051

The California Statewide Community Fault Model (SCFM) Version 3.0 is now a comprehensively reviewed and evaluated statewide model that consists of the southern California CFM 4.0 and more than 190 fault representations for northern California.

While CFM 4.0 was previously reviewed and formally released (Nicholson et al., 2014), in recent years, the northern California component also underwent substantial updates and improvements including the addition of about 40 new fault representations. To facilitate community review and a thorough evaluation of the updated, complete SCFM, a group of about 30 colleagues were invited to a well attended workshop hosted by the USGS at Menlo Park. For this review, a complete fault documentation spreadsheet of SCFM was prepared with identifying information, such as average strike and dip, and source material on each fault. As SCFM represents faults in 3D, we also developed a SCFM viewer based on SCEC VDO to enhance model visualization and comparison of 3D fault surfaces, imagery, Qfault traces and a catalog of relocated hypocenters. All materials and detailed evaluation instructions including ranking guidance were made available through a public web page. The workshop included members of the USGS, PG&E, Lettis, CGS and SCEC among others. It yielded two main results: often quite critical evaluations in the form of numerical and/or qualitative ranking of alternative fault representations, and strong guidance on future model improvements. Based on these evaluations, a set of 126 fault representations was selected to comprise a primary or preferred fault model within SCFM 3.0.

In southern California, as a result of recent updates, CFM 5.0 now contains 90 distinct fault zones, or separate fault systems, defined by over 300 individually named faults, with over 350 new or updated primary and alternative 3D fault representations added to CFM since Version 3.0. Improvements to CFM since 2014 include completion of an updated and expanded fault set for active faults in the Mojave, additional detailed faults in the offshore Borderland, and initial development of alternative models and an expanded fault set involved in the complex 3D deformation in the Ventura Special Fault Study Area. In addition, within the Gocad CFM environment, updated macros were developed to visualize focal mechanisms as beachballs or as selected nodal planes to better check for internal consistency between modeled CFM surfaces and dominant slip orientations in 3D.

Plesch, A., Shaw, J. H., Nicholson, C., Sorlien, C. C., & SCFM 2015 workshop participants, .. (2015). Evaluation of the Statewide Community Fault Model (SCFM) Version 3.0 and Continued Updates to the SCEC CFM 5.0. Poster Presentation at 2015 SCEC Annual Meeting.

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