SCEC Award Number 12108 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Evaluating 3D Fault Geometry in Special Fault Study Areas and Improving the SCEC Community Fault Model (CFM)
Investigator(s)
Name Organization
Craig Nicholson University of California, Santa Barbara
Other Participants Andreas Plesch, John Shaw and Egill Hauksson through related SCEC projects.
SCEC Priorities 4c, 4b, 4a SCEC Groups USR, Seismology, SoSAFE
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 This project is part of an on-going, multi-year effort within SCEC to systematically upgrade and improve the Community Fault Model (CFM). In 2012 and working in close cooperation with Andreas Plesch, John Shaw, and Egill Hauksson, we continued to make steady and significant improvements to the CFM and its associated fault database [Nicholson et al., 2012]. These improvements include more detailed and complex 3D representations of major active fault systems (Fig.1), additional detailed fault surface trace data, and finalization of our new naming and numbering scheme for CFM that allows for closer links to the USGS/CGS Quaternary fault database (Qfaults). A systematic revision of CFM fault models was triggered by unexpected discrepancies between previous CFM-v.3 fault representations and the newer Qfaults surface traces, as well as by the availability of extensive relocated earthquake catalogs to better define the complex subsurface geometry of active faults. A draft version of CFM-v.4 was sent out for review and comment; however, this upgrade to CFM-v.4 is not yet complete. Many fault models in CFM-v.3 still need to be re-registered to the more detailed Qfault surface traces and, together with recent relocated hypocenters, require newer, more complex and more realistic 3D fault models for CFM. This includes major faults within designated, past, or soon-to-be designated Special Fault Study Areas (SFSA). In 2012, this project was able to develop improved CFM 3D models for a number of these areas including Parkfield, San Gorgonio Pass, Laguna Salada-Sierra Cucapah and San Fernando-Northridge.
Intellectual Merit Many aspects of seismic hazard evaluation, including understanding earthquake rupture and geodetic strain, developing credible earthquake rupture scenarios, modeling geodetic and geologic fault slip rates, or predicting strong ground motion, are all strongly dependent on accurately resolving the 3D geometry of active faults at seismogenic depths. A considerable effort within SCEC has thus been focused on developing, updating and improving the SCEC 3D Community Fault Model (CFM). Such efforts to improve CFM are fundamental to SCEC’s primary research objectives if we are to better understand aspects of fault kinematics and accurately characterize the seismic behavior, subsurface geometry and stress evolution of major mapped fault systems. Having accurate and realistic 3D models of subsurface fault geometry is also particularly important when investigating the likelihood of multi-segment or multi-fault ruptures on major southern California faults. The primary purpose and intellectual merit of this project is thus to provide just such improved, more detailed 3D fault models for CFM. These 3D fault surfaces have already proven useful in developing more realistic dynamic earthquake rupture models along the San Andreas fault, as well as providing a better match to the observed patterns of uplift and topography along and across these active faults.
Broader Impacts Project personnel actively participate in a number of outreach and educational activities related to informing the public, students and various stakeholders of the earthquake and tsunami hazards of coastal and Southern California. This includes contributions to and participation in various workshops organized by local Emergency Response Teams and the County Office of Emergency Services in preparation for or associated with the annual California State-wide Earthquake ShakeOut drill. These activities help instruct people on how to better prepare for and respond to regional earthquake and tsunami hazards. This project also helps support and maintain various state-of-the-art interactive 3D visualization, analysis and modeling programs for use by students and researchers at UCSB for the interpretation, mapping and modeling of subsurface 3D fault structure and related syntectonic stratigraphy.
Exemplary Figure Figure 1. Oblique 3D view looking NE of new, revised CFM-v.4 fault representations developed in 2011 and 2012, plus Qfault surface traces (red lines), and relocated seismicity (dots color-coded by depth) [Nicholson et al., 2011; 2012]. New CFM 3D faults are now registered to the Qfault surface traces and major strike-slip faults are no longer assumed to be vertical, but change dip and dip direction along strike and with depth to better correlate with the relocated hypocenters. Seismicity from Hauksson et al. [2012].