We conducted a comprehensive analysis of the structural controls of geothermal systems within the Great Basin and adjacent regions. Our main objectives were to: 1) Produce a catalogue of favorable structural environments and models for geothermal systems. 2) Improve site-specific targeting of geothermal resources through detailed studies of representative sites, which included innovative techniques of slip tendency analysis of faults and 3D modeling. 3) Compare and contrast the structural controls and models in different tectonic settings. 4) Synthesize data and develop methodologies for enhancement of exploration strategies for conventional and EGS systems, reduction in the risk of drilling non-productive wells, and selecting the best EGS sites.

Phase I (Year 1) involved a broad inventory of structural settings of geothermal systems in the Great Basin, Walker Lane, and southern Cascades, with the aim of developing conceptual structural models and a structural catalogue of the most favorable structural environments. This overview permitted selection of 5-6 representative sites for more detailed studies in Years 2 and 3. Sites were selected on the basis of quality of exposure, potential for development, availability of subsurface data, and type of system, so that major types of systems can be evaluated and compared. The detailed investigations included geologic mapping, kinematic analysis, stress determinations, gravity surveys, integration of available geophysical data, slip tendency analysis, and for some areas 3D modeling. In Year 3, the detailed studies were completed and data synthesized to a) compare structural controls in various tectonic settings, b) complete the structural catalogue, and c) apply knowledge to exploration strategies and selection of drilling sites.