Regional Patterns of Geothermal Activity in the Great Basin Region, Western USA: Correlation with Strain Rates

Abstract

The regional patterns of geothermal activity in the western USA correlate directly with strain rates derived from GPS geodetic data. In the Great Basin region, geothermal fields are concentrated in discrete belts along the eastern margin of the Basin and Range (Wasatch Front) in western Utah and southeastern Idaho and in western to north-central Nevada within and directly northeast of the Walker Lane, which is a system of right-lateral faults accommodating ~20% of relative motion between the Pacific and North American plates. These two regions have higher current strain rates than other parts of the Basin and Range province. Enhanced extension in western to north-central Nevada probably results from the northwestward termination of the Walker Lane and the concomitant transfer of dextral shear into west-northwest directed extension, thus producing a broad transtensional region. High-temperature systems cluster within the zones of highest strain rate directly northeast of the Walker Lane, in areas of recent magmatism, or in particularly high-strain transtensional pull-apart basins along the Walker Lane or San Andreas fault system. The capacity of geothermal power plants also correlates with strain rates, with the largest (hundreds of megawatts) along the Walker Lane or San Andreas fault system, where strain rates range from 10-100 nanostrain/yr to 1,000 nanostrain/yr, respectively. Lesser systems (tens of megawatts) reside in the Basin and Range (outside the Walker Lane), where local strain rates are typically < 10 nanostrain/yr. These results may have implications for assessing and quantifying geothermal potential in other tectonically active regions.