Targeting of potential geothermal resources in the Great Basin from regional to basin-scale relationships between geodetic strain and geological structures

We apply a new method to target potential geothermal resources on the regional scale in the Great Basin by seeking relationships between geologic structures and GPS-geodetic observations of regional tectonic strain. First, we establish a theoretical basis for understanding how the rate of fracture opening can be related to the directional trend of faults within the regional-scale strain field. Second, we develop a strain-structure methodology that uses a digitized database of Quaternary fault strikes and velocities of GPS stations. Results of our strain-structure analysis on the regional scale show a spatial relationship between known geothermal activity and (1) change in the direction of fault orientations, (2) change in the direction of extensional strain, and (3) the magnitude of extensional strain, especially fault-normal extension associated with shear strain. In contrast, the dilitation component of strain is not a significant indicator of geothermal activity in the Great Basin. Using the observed relationships between strain and structure, the NE-SW trending Humboldt structural zone (HSZ) in north-eastern Nevada is clearly identifiable as a regional geothermal target. Based on our detection of an anomalous high in fault-normal extensional strain, we identify Buffalo Valley toward the NE extent of the HSZ as a potential geothermal target to be further explored using GPS. We therefore recommend investigating Buffalo Valley with fine spatial resolution (∼10 km rather than the current ∼100 km) using a dense GPS network to assess its geothermal potential, by comparison of strain-structure relationships with current power-producing areas within the HSZ.