SCEC Award Number 13086 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Terrestrial Lidar 3-Year Time-Series of Scarp Evolution on the El Mayor-Cucapah Rupture
Investigator(s)
Name Organization
Michael Oskin University of California, Davis
Other Participants Austin Elliott
SCEC Priorities 1, 2, 4 SCEC Groups Geology, SoSAFE, WGCEP
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 Annual post-earthquake surveys with tripod LiDAR document the onset of geomorphic processes including fissure fills, headward scarp erosion, and burial/erosion of uphill-facing scarps formed by the 4 April 2010 El Mayor- Cucapah earthquake. In total we have collected a three-year time-series of extremely high-resolution (~2000 pts/m2) topographic surveys along four ~250 m reaches of fresh scarps from the 2010 earthquake rupture in northern Baja California. Using iterative closest point minimization we coregister the scans in order to detect local geomorphic changes, i.e., erosion and deposition across the fault. The detected geomorphic changes are a quantified modern analog for the processes that paleoseismologists and structural geologists interpret to constrain past earthquakes. We find rapid, channelized erosion of the scarp where it cuts a hillslope domain, illuminating the extreme rate and variability of surface processes during the onset of scarp diffusion. We also document the deposition of a thick (20-80 cm) wedge of sand and silt upstream of an uphill-facing scarp, indicating the rapid (< 5 years post-event) emplacement of an important stratigraphic horizon for paleoseismic assessment in similar environments.
Intellectual Merit Through repeated terrestrial laser scanning of the 4 April 2010 El Mayor Cucapah earthquake scarps we constrain the rate, extent, and mode of geomorphic modification to coseismic fault scarps. Uncertainty in the interpretation, and thus reconstruction, of offset geomorphic features may be large and underreported because geologists often have little information to constrain the geomorphic history of offset features. Such uncertainties diminish the impact of geologic constraints in fault-system-wide models such as UCERF. One important approach to reducing these uncertainties is calibration of the evolution of fault-zone morphology with precise measurement of modern examples and processes. We took advantage of fresh earthquake rupture in the Sierra Cucapah to measure, using high-resolution LiDAR, the initial rate, volume, and style of geomorphic change across a fault scarp.
Broader Impacts This project involves extensive international collaboration CICESE, including participation of their students in the fieldwork and data analysis. Researchers from Arizona State and the Colorado School of Mines were also involved. LiDAR survey and GPS equipment were loaned by UNAVCO, strengthening collaboration with this research consortium. The project constitutes a portion of the Ph.D. thesis of U.C. Davis graduate student Austin Elliott, whom has taken the lead in all project elements, including international logistics, fieldwork, data analysis and interpretation.
Exemplary Figure Figure 2: Oblique perspective of the 2013 t-lidar point cloud at the bedrock hillslope scarp of the Borrego fault at “Site 2.” Points are colored by absolute distance from a reference point cloud collected 12 days after the earthquake, in April, 2010. Color scale has a minimum threshold of 5 cm and grades to red at ~25 cm distance. Direct point-cloud to point-cloud comparison quantifies zones of both exceptionally high (>1 m) erosion and areas of remarkably little modification. Here we see that the scarp crest has been removed from almost the entire reach of the rupture within this site.