Structural Inventory of Great Basin Geothermal Systems and Definition of Favorable Structural Settings

Structural controls of 426 geothermal systems in the Great Basin region including western Nevada, central Nevada, northwestern Nevada, northeastern Nevada, east-central Nevada, eastern California, southern Oregon, and western Utah were analyzed with literature research, air photos, Google Earth imagery, and/or field reviews. Of the systems analyzed, we were able to determine the structural settings of more than 240 sites. The structural catalogue is stored in a master spreadsheet included in this submission. Data components include structural setting, primary fault orientation, presence or absence of Quaternary faulting, reservoir lithology, geothermometry, presence or absence of recent magmatism, and distinguishing blind systems from those that have surface expressions.

Systems were cataloged into the following eight major groups, based on the dominant pattern of faulting:
- Major normal fault segments (i.e., near displacement maxima).
- Fault bends.
- Fault terminations or tips.
- Step-overs or relay ramps in normal faults.
- Fault intersections.
- Accommodation zones (i.e., belts of intermeshing oppositely dipping normal faults),
- Displacement transfer zones whereby strike-slip faults terminate in arrays of normal faults.
- Transtensional pull-aparts.

These settings form a hierarchal pattern with respect to fault complexity.
- Major normal faults and fault bends are the simplest.
- Fault terminations are typically more complex than mid-segments, as faults commonly break up into multiple strands or horsetail near their ends.
- A fault intersection is generally more complex, as it generally contains both multiple fault strands and can include discrete dilational quadrants.
- A step-over consists of two overlapping fault terminations and thus involves additional complexity, especially where the relay ramp is breached by multiple fault splays between the main overlapping faults and thus contains multiple fault intersections.
- Accommodation zones involve further complexity, as they contain multiple fault terminations and fault intersections.