SCEC Award Number 21023 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Expand the 3D Fault Set and Geologic Surface Library to Help Update & Improve SCEC Community Fault and Deformation Models
Name Organization
Craig Nicholson University of California, Santa Barbara
Other Participants Andreas Plesch, Christopher Sorlien, John Shaw, Scott Marshall, Egill Hauksson
SCEC Priorities 3a, 2e, 3e SCEC Groups CXM, SAFS, SDOT
Report Due Date 03/15/2022 Date Report Submitted 03/11/2022
Project Abstract
Since 2009, I and my colleagues Andreas Plesch and John Shaw have led the systematic update, expansion and improvement to the SCEC Community Fault Model (CFM), culminating in the release of CFM5.3 [Nicholson et al., 2019, 2020]. This on-going update represents a substantial improvement of 3D fault models for southern California. The CFM3 fault set was expanded from 163 faults to nearly 460 preferred faults organized into 107 complex fault systems, plus another 32 faults added or updated in 2021 [Nicholson et al., 2021]. Most of these updated or newly created 3D fault models (67%) were developed at UCSB. 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 Earthquake Gate or Special Fault Study Areas [Nicholson et al., 2012-2021]. These new models allow for more realistic, 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 2021, we continued to update, expand and improve the CFM fault set and associated database, adding updated or newly created 3D fault models primarily in the Ventura SFSA and Anza-Borrego region, as well as further updating and completing the metadata content for these newly added and older CFM faults.
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 continue 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 to update and improve the CFM underlying datasets and associated fault attribute 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, updated SCEC CFM webpage and new, interactive web-based CFM viewer interface — now with both 2D and 3D capability [Nicholson et al., 2018; Shaw et al., 2019; Su et al., 2019; Plesch et al., 2020; Marshall et al., 2021] provides easier user access to the digital CFM 3D fault set of complex fault representations and associated metadata of fault attributes, 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 2. (left) Geologic cross sections of subsurface structure and stratigraphy from correlated industry well data that help define the S-dipping Padre Juan and Sisar faults. (right) Oblique 3D view looking NW of Ventura Special Fault Study Area faults [Nicholson et al., 2021]. Faults not otherwise included in the released CFM5.3 preferred fault set (that were available in the CFM since 2016 or recently updated for 2021) are shown in red. As shown at left, fault geometry in upper 3-4 km is well defined based on industry well data [Hopps et al., 1992; Nicholson et al., 2017; Hughes et al., 2020], and to some extent at greater depths from seismicity [Nicholson et al., 2017, 2020, 2021].