SCEC Award Number 21060 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title NASA Collaborative Proposal: Crustal Deformation Time Series from InSAR and GNSS
Investigator(s)
Name Organization
David Sandwell University of California, San Diego Zhen Liu National Aeronautics and Space Administration Yehuda Bock University of California, San Diego Alejandro Gonzalez-Ortega Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (Mexico)
Other Participants Xiaohua Xu - postdoc
Katherine Guns - postdoc
SCEC Priorities 1a, 1b, 2a SCEC Groups Geodesy, CXM
Report Due Date 03/15/2022 Date Report Submitted 03/29/2022
Project Abstract
 Our 2021 proposal had two main components. The first part is to develop InSAR deformation time series using all Sentinel-1 acquisitions combined with all the cGNSS time series. This work will be done in collaboration with Zhen Liu at JPL as well as the participants in the Community Geodetic Model (CGM). The second part of our proposed investigation is to include cGNSS measurements from stations in Baja CA into the SCEC CGM. These stations are operated by Alejandro Gonzalez-Ortega at CICESE. Both parts contribute to the SCEC objectives discussed above.
Intellectual Merit Two of the top priorities of SCEC5 are (1) to better understand how faults are loaded across temporal and spatial scales and (2) to establish the role of off-fault inelastic deformation on strain accumulation, dynamic rupture, and radiated seismic energy. Surface crustal velocities and deformation time series are one of the key boundary conditions needed for addressing these problems. Several recent studies have shown that most damaging earthquakes occur in areas where the crustal strain rate exceeds about 50-100 nanostrain/yr [e.g., Kreemer et al., 2014; Elliot et al., 2016.; Zeng et al., 2018]. Many of these areas are heavily populated and have had major destructive earthquakes in the past. Moreover, one of the largest uncertainties of California earthquake hazard models (i.e., UCERF-3 [Field et al., 2014; Field et al., 2015]) is the amount of plate boundary deformation that is accommodated by off-fault strain and whether this strain is accumulating as elastic or as plastic deformation. Therefore, accurate strain rate measurements are needed to improve earthquake forecasts. To achieve an ideal 50-nanostrain/yr accuracy at a 10-km resolution (i.e., a typical fault locking depth) will require a 2-D horizontal velocity model that has an accuracy of 0.5 mm/yr. Currently GNSS provides this accuracy but not at 10-km spatial resolution; InSAR provides this spatial resolution but cannot yet achieve yet this accuracy. Here we propose a path to achieving this objective using combined GNSS and InSAR.
Broader Impacts The quality and quantity of GNSS and InSAR data are increasing rapidly and many groups are developing detailed crustal deformation models as part of the SCEC Community Geodetic Model (CGM). The overall objectives of the SCEC CGM are to develop a high spatial resolution (~500 m) crustal motion model consisting of velocities and time series for Southern California that leverage the complementary nature of GNSS and InSAR observations. Reprocessing of long GNSS time series has provided high accuracy vertical measurements that reveal a wide range of new hydrologic and tectonic signals [Hammond et al., 2016]. In addition, two new C-band InSAR satellites (Sentinel-1A and B) are providing highly accurate systematic coverage of the entire SCEC region every 6-12 days from two look directions. We (JPL and SIO) have developed new geometric alignment software to enable routine and systematic processing of this completely new type of InSAR data (TOPS-mode, Sansosti, et al., 2006; Prats-Iraola et al., 2012). Results from our 2020 work are summarized next.
Exemplary Figure Figure 4. Participants in the March 5-6, 2022 GPS field campaign across the Cerro Prieto Fault. Faculty and students from CICESE and Scripps Oceanography worked in collaboration to survey 31 monuments in two days.