Stanford Geothermal WorkshopFebruary 9-11, 2026

Favorable structural settings (FSS) along Quaternary faults control the location of many higher temperature geothermal systems in the Great Basin region (GBR) of the western USA, which includes most of NV, western UT, southern ID, southeast OR, and eastern CA. They include various fault interaction zones, such as terminations, intersections, step-overs (or relay ramps), and accommodation zones in normal fault systems, as well as pull-aparts and displacement transfer zones in the transtensional western part of the GBR. FSS are commonly critically stressed and characterized by structural complexity, closely-spaced faults, and greater proportions of fault breccia vs. fault gouge, all of which can enhance permeability and thus result in long-term, deeply rooted fluid flow. FSS are critical for vectoring into areas of greater permeability in known geothermal systems and for identifying potential locations of hidden geothermal systems. A major objective of the INGENIOUS project (INnovative Geothermal Exploration through Novel Investigations of Undiscovered Systems) is to generate new geothermal favorability maps for the GBR through compilation and integration of 16 regional geological and geophysical datasets, including FSS. Using available imagery (NAIP, Lidar), geological maps, and geophysical data (mainly gravity), we have identified greater than 1,430 FSS in the GBR. Each FSS was outlined with geologically grounded polygons, which collectively occupy ~7.7% of the study area. Step-overs were the most common accounting for ~40% of FSS followed by fault intersections (26.1%), fault terminations (16.7%), accommodation zones (6.8%), pull-aparts (2.3%), and displacement transfer zones (1.4%). For the 403 known geothermal systems in the GBR, with temperatures ≥37°C, step-overs are again the most common FSS (~27.5%) followed by fault intersections (22.1%), fault terminations (16.6%), accommodation zones (5.7%), displacement transfer zones (3.2%), pull-aparts (2.7%), and major normal faults (2.2%). For 120 systems with documented temperatures ≥120°C, which have been used as training sites for geothermal play fairway analyses, FSS include step-overs (34.2%), fault intersections (26.7%), fault terminations (14.2%), displacement transfer zones (6.7%), accommodation zones (5.8%), pull-aparts (5.0%), and major normal faults (1.7%). The greater than 1,430 FSS, 403 KGS, and 120 training sites in the INGENIOUS study area are all minimums. The number of KGS’s and training sites does not account for an unknown amount of hidden geothermal systems, which probably make up the bulk of geothermal resources in the GBR. Further, the lack of detailed geological (e.g., geological maps) and geophysical (e.g., gravity) datasets greatly limits identification of FSS, especially in the many basins. Notably, many FSS (e.g. fault tips and accommodation zones) are characterized by closely-spaced, relatively minor faults with minimal recent surface ruptures. Further, much of the GBR was inundated by late Pleistocene lakes, and thus faults that have not ruptured in the Holocene are obscured by lake sediments and shoreline features. Detailed gravity surveys are particularly crucial for delineating FSS within and along the margins of basins. Most basins contain multiple FSS, raising the question as to how many independent geothermal systems can such basins host. If such basins contain multiple systems, the geothermal potential of the GBR may be underestimated, especially considering that conductive heat envelopes conducive to EGS development may accompany convective systems. Regional assessments of FSS are therefore imperative for assessing and ultimately unleashing the full geothermal potential of the GBR.

Topic: Geology