Faults and Gravity Anomalies over the East Mesa Hydrothermal-Geothermal System

Abstract

Detailed interpretations of gravity anomalies over geothermal systems may be extremely useful for mapping the fracture or fault system that control circulation of the thermal waters. This approach seems to be particularly applicable in areas like the Salton Trough where reactions between the thermal waters and the porous sediments produce antigenic hydrothermal minerals in sufficient quantity to cause distinct gravity anomalies at the surface. A 3-D inversion of the residual Bouguer gravity anomaly over the East Mesa geothermal field was made to examine the densified volume of rock. We show that the data no only resolve a north south and an intersecting northwest structure, but that is may be possible to distinguish between the active present day hydrothermal system and an older and cooler part of the system. The densified region is compared spatially to self potential, thermal and seismic results and we find a good concordance between the different geophysical data sets. Our results agree with previous studies that have indicated that the main feeder fault recharging East Mesa reservoir dips steeply to the west.