SCEC Award Number 19031 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Evaluate & Refine 3D Fault and Deformed Surface Geometry to Update & Improve the SCEC Community Fault Model
Investigator(s)
Name Organization
Craig Nicholson University of California, Santa Barbara
Other Participants Andreas Plesch, Chris Sorlien, John Shaw, Egill Hauksson & Scott Marshall through related projects or CXM activities.
SCEC Priorities 3a, 3e, 2e SCEC Groups CXM, SAFS, Seismology
Report Due Date 03/15/2020 Date Report Submitted 03/10/2020
Project Abstract
 Since SCEC3, I and my colleagues Andreas Plesch, Chris Sorlien, John Shaw, Egill Hauksson, and now Scott Marshall continue to make steady and significant improvements to the SCEC Community Fault Model (CFM), culminating in the release of CFM-v5.3 [Nicholson et al., 2019]. This on-going systematic update represents a substantial improvement of 3D fault models for southern California. The CFM-v3 fault set was expanded from 170 faults to nearly 400 faults in CFM-v5.3 organized into 106 complex fault systems. Most of these updated 3D fault models were developed by UCSB, or to which UCSB made significant contributions. This includes all the major fault models of major fault systems (e.g., San Andreas, San Jacinto, Elsinore-Laguna Salada, Newport-Inglewood, Imperial, Garlock, etc.), and most major faults in the Mojave, Eastern & Western Transverse Ranges, Coast Ranges, offshore Borderland, and updated faults within designated Special Fault Study or Earthquake Gate Areas [e.g., Nicholson et al., 2012-2019]. These new models allow for more realistic, curviplanar, complex 3D fault geometry, including changes in dip and dip direction along strike and down dip, based on the changing patterns of earthquake hypocenter and nodal plane alignments and, where possible, imaging subsurface fault geometry with industry seismic reflection data. For 2019, access to the CFM and its associated fault database were enhanced through the new CFM webpage and interactive web-based viewer interface. In addition, we continued to update, expand and improve the CFM 3D fault set & associated database, as well as the underlying datasets used for model evaluation, development, and refinement.
Intellectual Merit This project supported continued development and enhancement of the CFM to facilitate its use in new community modeling efforts, fault systems studies, and probabilistic hazard assessments. As widely acknowledged, the CFM and its associated fault database are crucial components of SCEC, and are critical to many on-going SCEC activities, research objectives, program elements, and science initiatives. Having accurate and realistic 3D models of subsurface fault geometry is also important when investigating the likelihood of multi-segment or multi-fault ruptures. The primary purpose and intellectual merit of this particular on-going, multi-year project component was thus to provide just such improved, more detailed and more realistic 3D fault models for the CFM based on the distribution of improved fault surface trace data, relocated earthquake hypocenters, focal mechanisms, seismic reflection and well data. Besides updating, expanding and improving the CFM 3D fault set, the project also continued update and improve the CFM underlying datasets and associated fault database.
Broader Impacts In addition to providing updated and improved 3D fault models and interpretations of complex fault geometry for the CFM, this project also helped, in conjunction with Andreas, John, Scott and SCEC IT, to enhance the availability and accessibility of the SCEC CFM and, as a consequence, the broader impacts of the CFM to a wider range of earthquake science initiatives, community modeling efforts, and related student research activities. Development of the dedicated SCEC CFM webpage and new, interactive web-based CFM viewer interface [e.g., Nicholson et al., 2018; Shaw et al., 2019; Su et al., 2019] provides easier user access to the digital CFM 3D fault set of complex fault representations, allowing for comparative studies of such complex fault systems on a more global basis. In addition, at UCSB and Harvard, this project and its related collaborative component continued to support and encourage the use of state-of-the-art interactive facilities and software for the 3D visualization, analysis, interpretation and modeling of complex fault representations and underlying datasets — facilities and software that help promote research, education and student instruction in complex earth system science and earthquake investigations with the ultimate goal of improved earthquake hazard assessment and risk mitigation.
Exemplary Figure Figure 4. Oblique 3D view looking down-dip of updated Lytle Creek fault in the Cajon Pass EGA. Nodal planes (disks) parallel or sub-parallel to San Andreas and San Jacinto faults are steeply dipping (80°–90°) and define a sub-vertical zone of distributed right-lateral shear through the Pass. Nodal planes appear to define a NW extension of the Glen Helen fault (purple-dashed line) in the subsurface as compared to or beyond its mapped surface trace.
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