Understanding Fault Characteristics and Sediment Depth for Geothermal Exploration using 3D Gravity Inversion in Walker Valley, Nevada

Abstract

The Southern Walker Lake Basin, situated in the Walker Lake structural domain, consists of primarily E-W directed extension along N-NNW striking normal faults. Water well drilling on the eastern slopes of the Wassuk Range, west of the city of Hawthorne, Nevada showed elevated temperatures. Two recent drill holes reaching downhole depths of more than 4000 ft give some insight to the geologic picture, but more information would complete the understanding of the geothermal reservoir. Dense gravity coverage of the area, coupled with geologic mapping, enabled us to infer a right step in the range front normal fault in the same area where the drill data encountered high-temperature fluid. The right step in the normal fault system could open fractures in the rock, allowing for hot, upwelling fluids to migrate to the near surface. Many active geothermal systems appear in similar geologic and geographic settings in on-going exploration efforts. We have applied techniques developed by the mineral industry to understand basement depth and fault structure in the Southern Walker Lake Basin. We construct 2D density sections in the basin from gravity data to model fault structure and alluvium thickness, and combined these sections to produce a 3D surface of the basement structure. The 3D model of the bedrock surface agrees well with the geologic model, and shows steeply dipping faulting on the west side of the valley.