Shape and Dimensions of the Cerro Prieto Pull-Apart Basin, Mexicali, Baja California, Mexico, Based on the Regional Seismic Record and Surface Structures

Abstract

The Salton Trough is a wide, actively subsiding basin where a system of an en-echelon dextral transform faults and pull-apart basins is operating. This tectonic province represents the connection between the Gulf of California fault system and the San Andreas transform fault. Within the depression, several sub-basins, such as the Cerro Prieto geothermal field in Mexicali, Baja California, Mexico, represent an incipient spreading center along the southern limits of the Salton Trough. The Cerro Prieto Basin has developed between two major, subparallel, right-stepping active transforms, the Imperial and Cerro Prieto faults. General agreement exists regarding the regional tectonic interpretation of the Cerro Prieto Basin; however, published documentation is lacking regarding its shape and dimensions. In this paper, we address this problem. We have integrated seismic data available for the whole study area and evidence from surface breaks. Our study shows that the most important factor controlling formation of the Cerro Prieto pull-apart basin is the slip on the Cerro Prieto and Imperial faults. This tectonic activity has triggered subsidence in the intervening area, creating several subsurface normal faults, oriented oblique and parallel to the major strands, that control the subsidence. All of this has resulted in the development of a NE-SW trending, immature, pull-apart basin with an areal extent of 183 km2. Thus the Cerro Prieto Basin is an important structure in terms of geology and geothermal resources.