Anthropogenic Subsidence in the Mexicali Valley, B.C., Mexico, Caused by the Fluid Extraction in the Cerro Prieto Geothermal Field, and the Role of Faults

Abstract

The Cerro Prieto Geothermal Field (CPGF) is located in the Mexicali Valley in the southern part of the Salton Trough at the boundary between the Pacific and North American plates. The Valley is a zone of continuous tectonic deformation, geothermal activity, and seismicity.
Since 1973, fluid extraction at the CPGF has influenced deformation in the area, accelerating the subsidence and producing slip along tectonic faults. Subsidence and fault rupturing are causing damage to infrastructure like roads, railroad tracks, irrigation channels, and agricultural fields.
Detailed field mapping performed since 1989 in the vicinity of the CPGF shows that many subsidence induced fractures, fissures, collapse features, small grabens, and vertical displacements are related to known tectonic faults. The affected area is localized between the Cerro Prieto and Morelia faults to the NW and the Imperial and Saltillo faults to the SE, which limit the Cerro Prieto pull-apart basin (Suarez et al., 2008).
Since 1996, geotechnical instruments have operated in the Valley for the continuous recording of deformation phenomena. To date, the network includes three crackmeters, eight tiltmeters, and seven piezometers installed in the shallow aquifer. All instruments have sampling intervals ranging from 1  20 minutes.
Field and instrumental observations are analyzed in this paper to better understand how deep fluid extraction in the Cerro Prieto Geothermal Field (CPGF) has caused subsidence and produced slip in tectonic faults in the Mexicali Valley (Baja California, Mexico).