Targeting of Potential Geothermal Resources in the Great Basin from Regional Relationships between Geodetic Strain and Geological Structures

We report on an initial assessment of a new method to target potential geothermal resources on the regional scale. The method is based on seeking relationships between geologic structures and geodetic observations of regional tectonic strain. The working hypothesis is that geothermal plumbing systems might in some regions be controlled by fault planes acting as conduits that are continuously being stressed apart by tectonic activity. Specifically, this type of model would predict that geothermal activity would be spatially correlated with areas of high inter-seismic strain accumulation, especially when faults are favorably oriented with respect to the strain-rate tensor field. We tested these predictions in the Great Basin using tectonic velocity gradients derived from a network of Global Positioning System (GPS) sites, producing a regional strain-rate map with precision approaching a few parts per billion per year in some regions. Our initial conclusions are that regions of high interseismic strain accumulation correlate significantly with high geothermal well temperatures and the locations of geothermal power-producing sites. The next step is to test the prediction that fault orientation is also important, and that this information can be used to enhance the predictive capability of regional geodetic strain to target potential geothermal resources.