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Samsonov, SV, Feng WP, Fialko Y.  2017.  Subsidence at Cerro Prieto Geothermal Field and postseismic slip along the Indiviso fault from 2011 to 2016 RADARSAT-2 DInSAR time series analysis. Geophysical Research Letters. 44:2716-2724.   10.1002/2017gl072690   AbstractWebsite

We present RADARSAT-2 Differential Interferometric Synthetic Aperture Radar (DInSAR) observations of deformation due to fluid extraction at the Cerro Prieto Geothermal Field (CPGF) and afterslip on the 2010 M7.2 El Mayor-Cucapah (EMC) earthquake rupture during 2011-2016. Advanced multidimensional time series analysis reveals subsidence at the CPGF with the maximum rate greater than 100mm/yr accompanied by horizontal motion (radial contraction) at a rate greater than 30mm/yr. During the same time period, more than 30mm of surface creep occurred on the Indiviso fault ruptured by the EMC earthquake. We performed inversions of DInSAR data to estimate the rate of volume changes at depth due to the geothermal production at the CPGF and the distribution of afterslip on the Indiviso fault. The maximum coseismic slip due to the EMC earthquake correlates with the Coulomb stress changes on the Indiviso fault due to fluid extraction at the CPGF. Afterslip occurs on the periphery of maximum coseismic slip areas. Time series analysis indicates that afterslip still occurs 6years after the earthquake.

Gonzalez-Ortega, A, Fialko Y, Sandwell D, Nava-Pichardo FA, Fletcher J, Gonzalez-Garcia J, Lipovsky B, Floyd M, Funning G.  2014.  El Mayor-Cucapah ( M-w 7.2) earthquake: Early near-field postseismic deformation from InSAR and GPS observations. Journal of Geophysical Research-Solid Earth. 119:1482-1497.   10.1002/2013jb010193   AbstractWebsite

El Mayor-Cucapah earthquake occurred on 4 April 2010 in northeastern Baja California just south of the U.S.-Mexico border. The earthquake ruptured several previously mapped faults, as well as some unidentified ones, including the Pescadores, Borrego, Paso Inferior and Paso Superior faults in the Sierra Cucapah, and the Indiviso fault in the Mexicali Valley and Colorado River Delta. We conducted several Global Positioning System (GPS) campaign surveys of preexisting and newly established benchmarks within 30km of the earthquake rupture. Most of the benchmarks were occupied within days after the earthquake, allowing us to capture the very early postseismic transient motions. The GPS data show postseismic displacements in the same direction as the coseismic displacements; time series indicate a gradual decay in postseismic velocities with characteristic time scales of 669days and 203days, assuming exponential and logarithmic decay, respectively. We also analyzed interferometric synthetic aperture radar (InSAR) data from the Envisat and ALOS satellites. The main deformation features seen in the line-of-sight displacement maps indicate subsidence concentrated in the southern and northern parts of the main rupture, in particular at the Indiviso fault, at the Laguna Salada basin, and at the Paso Superior fault. We show that the near-field GPS and InSAR observations over a time period of 5months after the earthquake can be explained by a combination of afterslip, fault zone contraction, and a possible minor contribution of poroelastic rebound. Far-field data require an additional mechanism, most likely viscoelastic relaxation in the ductile substrate.

Fialko, Y, Simons M.  2000.  Deformation and seismicity in the Coso geothermal area, Inyo County, California: Observations and modeling using satellite radar interferometry. Journal of Geophysical Research-Solid Earth. 105:21781-21793.   10.1029/2000jb900169   AbstractWebsite

Interferometric synthetic aperture radar (InSAR) data collected in the Coso geothermal area, eastern California, during 1993-1999 indicate ground subsidence over a similar to 50 km(2) region that approximately coincides with the production area of the Coso geothermal plant. The maximum subsidence rate in the peak of the anomaly is similar to 3.5 cm yr(-1), and the average volumetric rate of subsidence is of the order of 10(6) m(3) yr(-1). The radar interferograms reveal a complex deformation pattern, with at least two irregular subsidence peaks in the northern part of the anomaly and a region of relative uplift on the south. We invert the InSAR displacement data for the positions, geometry, and relative strengths of the deformation sources at depth using a nonlinear least squares minimization algorithm. We use elastic solutions for a prolate uniformly pressurized spheroidal cavity in a semi-infinite body as basis functions for our inversions. Source depths inferred from our simulations range from 1 to 3 km, which corresponds to the production depths of the Coso geothermal plant. Underpressures in the geothermal reservoir inferred from the inversion are of the order of 0.1-1 MPa (except a few abnormally high underpressures that are apparently biased toward the small source dimensions). Analysis of the InSAR data covering consecutive time intervals indicates that the depths and/or horizontal extent of the deformation sources may increase with time. This increase presumably reflects increasing volumes of the subsurface reservoir affected by the geothermal exploitation. We show that clusters of microearthquakes associated with the geothermal power operation may result from perturbations in the pore fluid pressure, as well as normal and shear stresses caused by the deflation of the geothermal reservoir.