Updating the 3D fault set for the SCEC Community Fault Model (CFM-v4) and revising its associated fault database

Craig Nicholson, Andreas Plesch, Christopher C. Sorlien, John H. Shaw, & Egill Hauksson

Published September 2013, SCEC Contribution #2053

We continue to upgrade and improve the SCEC Community Fault Model (CFM) and to register updated CFM faults to the digital USGS Quaternary fault surface traces. New, revised 3D fault models for several major faults are now available, including the San Andreas from Parkfield to Cajon Pass, Garlock, Imperial-Brawley, Hollywood-Raymond, Landers-Joshua Tree, Lenwood-Lockhart, Laguna Salada-Indiviso, Sierra Cucapah, Oak Ridge-Northridge, San Gabriel, Santa Susana, San Fernando, Verdugo, Sierra Madre-Cucamonga and other faults, as well as for several intervening cross faults. Preliminary 3D models were also added for offshore Inner Borderland faults, including Carlsbad, Coronado Bank, Descanso, as well as others in the onshore and offshore Ventura and Santa Maria basins. These new models expand the lexicon of revised 3D fault models previously developed for CFM-v4 that include the San Andreas fault (SAF) from San Gorgonio Pass to the Salton Sea, the adjacent Mecca Hills-Hidden Springs, the San Jacinto, the Elsinore-Laguna Salada and the Agua Tibia-Earthquake Valley fault systems. These new models allow for more non-planar, multi-stranded 3D fault geometry, are more consistent with alignments of relocated hypocenters and focal mechanism nodal planes, and have a higher concentration of hypocenters within close proximity (±1 km) of the modeled 3D slip surface. The new 3D fault models also help characterize a more complex pattern of fault interactions at depth between various fault sets and linked fault systems. Along the SAF through San Gorgonio Pass, this includes blind, sub-parallel, en echelon oblique faults beneath the pass, a new model for the San Gorgonio Pass thrust and its relation to the North Palm Springs fault, and fault models for the Crafton Hills complex. Fault splays and secondary strands for the steep-to-west-dipping Laguna Salada-Indiviso fault were updated, and their spatial relationship to the steep-to-east-dipping strands of the Sierra Cucapah fault and cross faults in the Yuha Desert were better resolved. With this expanded CFM fault set, we finalized our new fault ID hierarchical name and numbering scheme for the associated fault database. However, this process of updating 3D fault models and continued model evaluation for CFM is still on-going. We received a number of rankings and reviews of previous CFM faults, and strongly encourage participation by the SCEC community to help us further review and improve these latest 3D fault models for CFM.

Citation
Nicholson, C., Plesch, A., Sorlien, C. C., Shaw, J. H., & Hauksson, E. (2013, 9). Updating the 3D fault set for the SCEC Community Fault Model (CFM-v4) and revising its associated fault database. Poster Presentation at SCEC Annual Meeting 2013.