SCEC Award Number 11061 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Building a Holocene slip history for the Mojave section of the San Andreas Fault
Name Organization
Eric Cowgill University of California, Davis Kate Scharer Appalachian State University Ryan Gold USGS Geologic Hazards Science Center
Other Participants O'Banion, Tracy Compton (MS student at UC Davis)
SCEC Priorities A1, A2, C SCEC Groups Geology, SoSAFE, WGCEP
Report Due Date 02/29/2012 Date Report Submitted N/A
Project Abstract
The goal of this project was to determine the extent to which the Holocene history of slip along the Mojave section of the San Andreas fault (MSAF) is recorded by displaced landforms. To address this problem we used both high resolution topographic data from existing airborne and new ground-based LiDAR measurements and new software tools that enable virtual-reality based visualization and analysis of such data. We have identified 58 faulted landforms with offsets ranging from 20 to 297 m along a 100-km-long section of the MSAF. At ten of these sites we used field and remote observations to map the surficial geology in detail, and have then reconstructed the sites to determine their suitability for future slip rate determinations. At 10 additional sites we have determined the offset magnitude and associated and maximum and minimum uncertainty bounds.
Intellectual Merit This study has identified a number of new potential slip-rate sites along the MSAF. Future geochronologic measurements at these sites should make it possible to construct a robust history of Holocene slip along MSAF, and thereby improve understanding of the apparently discrepant geodetic and geologic slip rates here. In addition, we have developed new insights into how to characterize the epistemic uncertainties associated with channel reconstructions.
Broader Impacts The project forms the core of the MS thesis work for graduate student Tracy Compton. The project also led to the development of a new software tool by collaborating computer scientists in the Keck CAVES group at UC Davis. We used this tool heavily to interactively reconstruct the sites. This tool allows the user to interactively reconstruct fault slip by defining a piecewise linear fault plane and incrementally moving one block relative to the other in any direction on the plane.
Exemplary Figure Figure 2: Plot summarizing the offset landforms along the MSAF. Grey bars indicate portions of the Holocene slip history that are constrained by observations. Gaps in that record are shown in white. Top panel shows previously reported results, bottom panel indicates results from present study, with data points color-coded the same as in Figure 1. There are additional published data points below 20m and above 360m that are not included here because they outside the Holocene offset range considered here. Figure created by Tracy Compton and Eric Cowgill