SCEC Award Number 19123 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Time-series analysis of fault creep rates within the Salton Trough of the Southern San Andreas Fault constrained from a decade of repeat-pass NASA UAVSAR radar imagery
Investigator(s)
Name Organization
Chelsea Scott Arizona State University Chandrakanta Ojha Arizona State University Manoochehr Shirzaei Arizona State University Ramon Arrowsmith Arizona State University
Other Participants
SCEC Priorities 1a, 2a, 3e SCEC Groups Geodesy, Geology, SDOT
Report Due Date 03/15/2020 Date Report Submitted 03/13/2020
Project Abstract
 Our project focuses on imaging active deformation along the San Andreas Fault. We proposed to use imagery from NASA’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) to constrain the creep behavior and explore approaches to optimize time-series approaches along the San Andreas Fault. These observations of surface deformation measure fault creep rates, the distribution and magnitude of off-fault deformation, and potential variations in creep rate along the fault. Our project’s goal is aligned with SCEC5’s task to integrate archived data from SAR satellites into the Community Geodetic Model.

There are three major components of our project. In Section 2, we discuss our processing of multiple UAVSAR flight lines along both the southern and central San Andreas Fault. In Section 3, we discuss the 40 km of high resolution topography that we acquired using a small Uncrewed Aerial System (sUAS) from Painted Canyon to Bombay Beach along the southern San Andreas Fault. This dataset that we will publish on OpenTopography will support future geodetic work aimed at measuring fault creep-related displacements. In Section 4, we illustrate how we applied SAR time-series and topographic differencing methods to resolve fault slip rate and examine the localization of deformation along the creeping portion of the central San Andreas Fault. We recently submitted a manuscript to the Journal of Geophysical Research: Solid Earth based on this work. The manuscript acknowledges this award (SCEC Contribution #10043).
Intellectual Merit Our work largely focused on the first two questions of SCEC’s strategic framework: (1) How are faults loaded on different temporal and spatial scales? (2) What is the role of off-fault inelastic deformation on strain accumulation, dynamic rupture, and radiated seismic energy? In terms of the methods, we worked on processing UAVSAR imagery along creeping portions of the San Andreas fault. We also refined approaches for performing 3D ICP differencing of high-resolution topograpghy data to detect fault creep along and adjacent to creeping faults. We applied these topographic differencing methods to the central San Andreas Fault at the Dry Lake Valley site where we calculated the fault creep rate. We showed that deformation is highly localized to the fault due to the fact that the fault is well-aligned for strike-slip motion. Our research addresses how the faults are loaded and the localization of strain accumulation.
Broader Impacts We completed a field campaign where we collected 40 km of UAS (i.e., drone) data along the southern San Andreas Fault. The field campaign included an undergraduate and graduate student who learned about SCEC, examined the geology surrounding the San Andreas Fault, and learned about conducting geophysical surveys along active faults.
Once we will have completed processing the UAS data, we will submit our processed data to OpenTopography where the dataset will be widely accessible to the SCEC, educational, and broader community. We will work with OpenTopography to promote this dataset, including writing a blog post for OpenTopography. This will promote both the dataset as well as earthquake science.
Exemplary Figure Figure 5: Fault offset derived from the topographic differencing of the 2007 EarthScope Northern California airborne lidar and 2017 UAS structure-from-motion topography at the Dry Lake Valley paleoseismic site (36.468, -121.055) along the creeping portion of the central San Andreas Fault. By comparing surface displacements on either side of the fault, we find an creep rate of 2.5±0.2 cm/yr at the Dry Lake Valley site.