Assembly of the Community Geodetic Model and GPS Survey of the Imperial and Cerro Prieto Faults [PI: Dr. David Sandwell, SIO-UCSD]
This project has two main components. The first part is to continue the assembly of the SCEC CGM. This involves developing consensus models from a suite of published models, urging the community to work toward consensus models, and upgrading the components of the CGM as new GPS and InSAR data become available. The second part of our proposed investigation is to continue a campaign GPS and InSAR analysis of the Imperial, Cerro Prieto and nearby faults in the Mexicali region of northern Baja California, MX. This is a collaborative effort between scientists at CICESE and SIO.
GPS velocity in northern Baja California in North America fixed reference frame. Black arrows are CGPS data. Blue arrows are GPS survey mode data. Green dots are the DD and CC arrays extended monuments. Inset: GPS survey mode installation setup.
Postseismic deformation and stress transfer after the 2010 El Mayor-Cucapah (Baja California) earthquake [PI: Dr. Eric Fielding, JPL-NASA]
The 4 April 2010 magnitude (Mw) 7.2 El Mayor-Cucapah earthquake ruptured a series of faults in Baja California, Mexico causing extensive damage in the Mexicali Valley and adjacent areas of southern California, USA. We have been studying the deformation of the Earth’s surface and seismic data to understand which faults moved during the earthquake and how much they moved. This is called coseismic deformation. After the main earthquake, there have been a large number of aftershocks and there is also other ongoing deformation, which is called postseismic deformation.
This postseismic deformation is the response of the Earth’s lithosphere (crust and upper mantle) to the redistribution of stress caused by the large earthquake. The idea is to determine physical properties of the Earth’s crust and upper mantle by comparing the postseismic deformation to models of the geophysical processes involved in the response to large earthquakes. These models can also be used to estimate how stress within the crust and mantle is transferred, both immediately by the earthquake and by the postseismic processes, to faults near the earthquake. Our modeling will enable us to constrain the evolution of crustal stresses, providing important insights for the assessment of future earthquake risk in northwestern Mexico and southwestern USA.
UAVSAR footprints (green frames) for the El Mayor-Cucapah postseismic study. The figure also includes CGPS (big red and blue dots), as well as, survey GPS sites (small red and blue dots). Inset: C20-A (Gulfstream III) airplane.
NASA has a radar system called Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR). The UAVSAR system is contained in a pod that was connected to the NASA C20-A (Gulfstream III) piloted airplane for this project. The NASA Gulfstream III has been specially modified to be capable of repeating the same path over the Earth’s surface within a distance of about 5 m, a unique capability that is essential for acquiring data for the InSAR analysis of ground deformation. A key part of the study will combine interferometric synthetic aperture radar (InSAR) analysis of satellite and airborne radar imagery with Global Positioning System (GPS) analysis to estimate the distribution of coseismic fault ruptures, and to measure the postseismic deformation.
ALOS-2 geodetic measurements of the subduction zone in Mexico: implications to large earthquakes and seismic hazard [PI: Dr. Alejandro Gonzalez-Ortega]
Slow slip events (SSEs) have been observed in most subduction zones with dense geodetic and seismic networks, primarily on the Japan and Cascadia subduction zones. New detailed GPS and Interferometric Synthetic Aperture Radar (InSAR) studies in the Mexican subduction zone are providing additional observations of slow slip phenomena in the Guerrero Gap, which hosted one of the largest SSEs (Mw 7.5) observed to date. Nonetheless, it still remains unclear how SSEs change the stress field in the Guerrero region and what would be the potential implications for future large earthquakes and seismic hazard in Mexico City. This proposal aims to integrate ALOS-2 InSAR time-series analysis and observations from the newly developed continuous GPS/Met network in Mexico (TLALOC Net) to estimate the spatial extent and magnitude of surface deformation, as a baseline reference frame for SSEs and earthquakes on the Mexican subduction zone.
Tectonic setting of the subduction zone in southern Mexico. Sense of relative motion between Cocos and North American Plates is represented with red outline arrows. Blue starts indicate the historic seismicity, Mw>7.0 since 1911. Red circles denotes permanent GPS stations (TLALOCNet). Green rectangles indicate the coverage of the ALOS-2 radar images.