SCEC Award Number 19083 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title NASA Collaborative Proposal: Crustal Deformation Time Series from InSAR and GPS
Investigator(s)
Name Organization
David Sandwell University of California, San Diego Xiaohua Xu University of California, San Diego Zhen Liu National Aeronautics and Space Administration Alejandro Gonzalez-Ortega Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (Mexico)
Other Participants Yao Yu - first year graduate student
Sandra Slead - first year MS student
SCEC Priorities 1a, 1b, 2a SCEC Groups Geodesy, CXM, Geology
Report Due Date 04/30/2020 Date Report Submitted 10/28/2020
Project Abstract
 Our investigation has two main components. The first part is to continue to contribute to the SCEC CGM. Work will be done in collaboration with NASA investigator Zhen Liu. The specific tasks are to:
- Develop InSAR time series for the SCEC region using Sentinel-1 data and continuous GPS (cGPS) time series (2015.5 until the present). Two groups, using different software and methods will independently construct time series (ISCE – Zhen Liu at JPL; GMTSAR – Xiaohua Xu at SIO).
- Meet quarterly (telecon) to compare results and refine best practices.
- Automate the entire process on a 12-day cadence including: data download; re-frame raw products; align the new SLC image to the stack; form interferograms going back ~60 days, align the LOS deformation to cGPS data (optional), update displacement time series, and deposit high level products at UNAVCO.
- Participate in the CGM and associated workshops for product feedback and updates.
- Use results for scientific investigations.

The second aspect of our research is to perform and analyze campaign GPS measurements of the Imperial and Cerro Prieto Faults in northern Baja California, MX. Over the past seven years, we have deployed and measured two GPS arrays across the Imperial and Cerro Prieto faults; and recently, two additional GPS arrays across the Indiviso and Tulecheck faults to better characterize the velocity gradient in the region. The proposed 2019 campaign will provide improved estimates of velocity gradient across the Tulecheck and Indiviso Faults.
Intellectual Merit The focus of this research is to improve the estimates of seismic moment accumulation rate on the fault systems of Southern California and Northern Baja, MX. This is accomplished using crustal deformation measurements from GPS and radar interferometry. During this period we developed new GPS/InSAR integration methods using the new InSAR data being provided by the Sentinel-1A and B spacecrafts.
Broader Impacts Funding for this research supported postdoc Xiaohua Xu. He provided near real time maps of radar interferometry products to USGS and other first responders following the July 2019 Ridgecrest Earthquakes. These were used to locate and map surface fractures. In addition, collaborative field work with scientists and students at CICESE, Ensenada MX, has enhanced US Mexican relations at both programatic and personal scientific levels.
Exemplary Figure Figure3. InSAR product for the 2019 Ridgecrest earthquake sequence. (previous page left) Unwrapped InSAR line-or-sight deformation from descending track 71 of Sentinel-1, with red colors denoting motion toward satellite and blue color denoting motion away from the satellite. (previous page right) Decomposed east-west deformation map after combining information from descending track 71 and ascending track 64 and high-pass filtering at 800 m. Red colors are eastward motion and blue colors are westward motion. (bottom left) Phase gradient map along the azimuth (flight) direction from descending track 71, with white colors denoting positive phase change along azimuth, and black colors denoting negative phase change. This is a stack of 4 interferograms to reduce noise. (bottom right) Derived fracture motion when combining information from the decomposed east-west motion and phase gradient map. Red lines represent right lateral fracture and blue line represent left lateral fracture.
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