The SCEC Community
Fault
Model Version 5.0: An Updated And Expanded 3D
Fault
Set For Southern California
Abstract
A major goal of the Southern California Earthquake Center is to improve estimates of earthquake hazard and predictions of strong ground motion by using more realistic models of 3D fault
geometry in its earthquake rupture forecasts. To this end, SCEC has developed and continually updates its Community
Fault
Model (CFM), a digital 3D representation of major active
fault
surfaces for the region. Here we present a new release of CFM (Version 5.0) that includes a number of major improvements, including refinement and additions of new 3D
fault
surfaces using primarily detailed
fault
surface trace, industry well, seismic reflection, relocated hypocenter and focal mechanism nodal plane data. CFM 5.0 now contains 90 distinct
fault
zones or separate
fault
systems defined by over 300 individually named faults with 625 primary and alternative 3D
fault
representations, and includes an updated
fault
database with an improved hierarchical
fault
naming and numbering system. The results document a wide variety of complex
fault
deformation styles, including: various aspects of strain partitioning and
fault
-related folding; sets of both high-angle and low-angle faults that mutually interact; blind and emergent structures; significant non-planar, multi-stranded faults with variable dip along strike and with depth; and active mid-crustal detachments at different structural levels. In places, closely-spaced
fault
strands or
fault
systems can remain surprisingly subparallel to seismogenic depths, while in other areas, major strike-slip to oblique-slip faults can merge or diverge with depth. An good example is in the Ventura-Santa Barbara area, where new
fault
models – that include a substantially revised set of alternative representations for the Ventura, Pitas Point, North Channel, Red Mountain, Mission Ridge, Santa Ynez, San Cayetano, Oak Ridge and Simi-Santa Rosa faults – were developed that indicate many of these
fault
systems tend to merge at depth. The updated CFM 3D
fault
surfaces thus help characterize a more complex pattern of
fault
interactions at depth between various
fault
sets and linked
fault
systems, and a more complex
fault
geometry than typically inferred or expected from projecting near-surface data down-dip, or modeled from surface strain and potential field data alone. CFM 5.0 is provided as a series of digital, triangulated
fault
surfaces, and is available by browsing to the SCEC-CFM webpage accessible from the structure.harvard.edu website.
AAPG Datapages/Search and Discovery Article #90215 © 2015 Pacific Section AAPG Convention, Oxnard, California, May 3-6, 2015