SCEC Award Number 14031 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Improving the Community Geodetic Model with GPS and InSAR
Name Organization
David Sandwell University of California, San Diego Xiaopeng Tong University of California, San Diego Jose Javier Gonzalez-Garcia Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (Mexico) Bridget Smith-Konter The University of Texas at El Paso Yuehua Zeng United States Geological Survey
Other Participants Alejandro Gonzalez - PhD student CICESE, Emmanuel Garcia - PhD student SIO
SCEC Priorities 1d, 2d, 1e SCEC Groups Geodesy, Transient Detection, EFP
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
One of the priorities of SCEC4 is to investigate stress transfer from plate motion to crustal faults. Surface crustal velocities are one of the key boundary conditions needed for developing 3-D stress rate models. The quality and quantity of GPS and InSAR data are increasing rapidly and many groups are developing detailed crustal velocity models. We have identified two areas of weakness in these models - the southernmost SAF system in the Mexicali Valley and the small-scale deformation near faults having shallow interseismic slip. Over the past year we have: collaborated with other SCEC and PBO scientists to develop a time-dependent Community Geodetic Model (CGM) at variable spatial resolution; worked with CICESE scientists to acquire spatially dense GPS velocities across the Imperial and Cerro Prieto Faults and; participated in SCEC workshops related to the development of the Community Geodetic Model as well as the Community Stress Model
Intellectual Merit The San Andreas Fault System (SAFS) is a natural laboratory for investigating the physics of the earthquake cycle along a major continental transform boundary. Two of the key parameters that can be used for seismic hazard assessment are seismic moment accumulation rate and strain accumulation rate. The GPS component of the Plate Boundary Observatory (PBO) provides accurate vector velocities (< 1 mm/yr accuracy) at a spacing of 10 to 20 km along the SAFS. However, the velocity gradient (strain rate) varies most rapidly within 20 km of the major faults, so strain rate is not well resolved by the GPS data alone. Radar interferometry (InSAR) provides deformation maps at 100 m spatial resolution, although factors such as temporal decorrelation and atmospheric path errors have made it difficult to achieve this full resolution with sufficient precision to improve upon the GPS measurements. The primary focus of our research is to construct high spatial resolution vector surface deformation measurements by combining the high accuracy point measurements provided by PBO GPS data with the high spatial resolution InSAR measurements.
Broader Impacts These proposed research activities will contribute to the objectives of SCEC by further advancing our understanding of fault system crustal dynamics, earthquake hazards, and data synthesis. The fundamental earthquake science being explored by this research has substantial societal relevance, as earthquake cycle strain rate estimates are poised to help mitigate seismic hazards.
Exemplary Figure Figure 1. Coulomb stressing rates in the El Mayor-Cucapah (EMC) rupture zone due to fluid extraction at the Cerro Prieto Geothermal Field (CPGF). Typical values are 20 kPa/yr and this plant has been in full operation for > 20 years so the integrated stress change is perhaps 400 kPa. The F1, F2 and F3 subevent fault planes are shown for reference, with the assumed hypocentral depth of 5 km marked with a red dashed line. The color scale ranges from -30 to 30 kPa/year, with contours displayed in increments of 10 kPa/year. Coulomb stressing rate at 5 km depth are plotted for the fault geometries of: (a) the Mw 4.3 foreshock (strike = 187°, dip = 79°, rake = 5°), (b) the F1 EMC subevent (strike = 355°, dip = 45°, rake = -80°), (c) the F2 EMC subevent (strike = 312°, dip = 75°, rake = -180°), and (d) the F3 EMC subevent (strike = 131°, dip = 60°, rake = -180°).[ Trugman et al., 2014]