Ground Deformation at the Los Humeros Geothermal Field (Mexico) Inferred by InSAR
Eszter BÉKÉSI, Peter A. FOKKER, Jon LIMBERGER, Damien BONTÉ, Joana ESTEVES MARTINS, Jan-Diederik VAN WEES
[Utrecht University, Netherlands]
Surface deformation can be detected with satellite-based geodetic sensors, providing important insights on subsurface geomechanical properties. In this study, we use Interferometric Synthetic Aperture Radar (InSAR) observations to measure ground deformation due to fluid extraction and due to an induced seismic event at the Los Humeros Geothermal Field (Puebla, Mexico). The result of the PS-InSAR (Persistent Scatterer by Synthetic Aperture Radar Interferometry) analysis shows that the subsidence at the LHGF was up to 8 mm/year between April 2003 - March 2007, which is small relative to the produced volume of 5x106 m3/year. The subsidence pattern indicates that the geothermal field is controlled by sealing faults separating the reservoir into several blocks. Our models imply small volume changes in the reservoir and the different nuclei of strain solutions differ only slightly. These findings suggest that the pressure within the reservoir is well supported and that reservoir recharge is taking place. The occurrence of induced seismicity is independent evidence for the development of effective stresses. The inversion of the coseismic deformation due to the 8 February 2016, Mw 4.2 earthquake showed activation of a shallow normal fault in a reverse manner. Even with the limited compaction observed from the subsidence, the stress development was enough to induce seismicity. Pore pressure contrasts over a fault will increase the stress development. However, the fault structure will be more complex than assumed in the present study, because an acceptable joint match of ascending and descending surface movement data was not possible. An integrated study into the complex reservoir behavior and the associated stress development over complex faults is therefore warranted.
|        Topic: Geophysics||Paper Number: 13201|