SCEC Award Number 21147 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Slip rate of the Simi-Santa Rosa fault and related structures
Investigator(s)
Name Organization
Reed Burgette New Mexico State University Katherine Scharer United States Geological Survey
Other Participants Brian Schrotenboer, NMSU M.S. student
SCEC Priorities 1a, 3a, 2e SCEC Groups Geology, SAFS, SDOT
Report Due Date 03/15/2022 Date Report Submitted 11/14/2024
Project Abstract
 The goals of this project were to document late Quaternary deformation along the Simi-Santa Rosa fault (SSRF) using field and remote sensing methods applied to geomorphic features and date prominent fluvial surfaces that cross the fault trace. Urbanization along the northern margin of Simi Valley has obscured geomorphic relationships along the fault trace, and we used archival aerial imagery to produce a high-resolution point cloud model of topography of the area including Simi Valley and the southern Santa Susana Mountains as it existed in 1947. We dated fluvial terrace fill below prominent geomorphic surfaces at three sites in the hanging wall of the SSRF using radiocarbon. Field observations and ages show several meters of sediment aggradation in major drainages in the hanging wall in the last 2000 years, with a widespread, upper surface that likely stabilized in the last 500-200 years. Analysis of multiple swath profiles extracted from the photo model point cloud on this late Holocene geomorphic surface across the fault suggests the presence of a ~1 m high scarp prior to development, although the elevation data are more noisy than modern lidar.
Intellectual Merit The landscape of Southern California has been extensively altered by urbanization. This project demonstrates the ability to reconstruct a high resolution (~ 1 m) model of topography from archival aerial photos that predate much of the development. We developed analysis strategies to measure late Quaternary deformation from the photogrammetric point cloud. Information about surface ages and slip history of the Simi-Santa Rosa fault contributes to our understanding of how plate boundary strain is accommodated in the southwestern Transverse Ranges and how seismic hazard is distributed in the region.
Broader Impacts This project supported training and research of M.S. student Brian Schrotenboer at NMSU. The methods that we adapted and developed will contribute to future work using high-resolution topography to measure tectonic deformation. The results will contribute to more accurate seismic hazard forecasts for this populated region as there are limited published reports describing the recent tectonic history of this fault.
Exemplary Figure Figure 1. Perspective view of the 1947 point cloud looking northeast across Simi Valley to the crest of the Santa Susana Mountains. The point cloud has over 300M points, and is colored by the grayscale value of photos used to construct the 3-D topography. The Simi-Santa Rosa fault makes the prominent break in slope between hills to the north and the agricultural Simi Valley.
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