Using Geodesy to Explore Correlations between Crustal Deformation Characteristics and Geothermal Resources

摘要

The Great Basin is characterized by non-magmatic geothermalfields, which we hypothesize are created, sustained, and controlled by active tectonics. We present geodetic velocities from the MAGNET (Mobile Array of GPS for NEvada Transtension) network that we use to infer relationships between the spatial variation in the style of geodetically inferred crustal deformation and the locations of existing geothermal systems. The velocity results from the MAGNET network are consistent and close to expectations based on analysis of prior networks, although MAGNET time-series at present are relatively short (0.8-2.2 yr), and any interpretation should be considered preliminary. We use the new velocities, supplemented with those from the BARGEN and USGS networks, to model the deformation field with two complementary approaches. In the first we determine the strain rate tensor field everywhere in our study area, and in the second we solve for rotations of pre-defined crustal blocks and the slip on the blocks' fault boundaries. We conclude from the preliminary results that there is a positive correlation between existing geothermal systems and areas that are either under transtension or that are in areas of transition between different deformation styles, such as in the Carson Sink area. The only exception to these inferred correlations is the geothermal activity in Dixie Valley. This discrepancy may be attributable to imperfections in the postseismic relaxation model that is used to correct the observed velocities for upper mantle viscoelastic relaxation following large historic earthquakes, which are themselves based on preliminary data. Our results suggest high favorability in some yet unexplored regions such as the Carson City Valley and the northeastern Carson Sink.