Geothermal production and reduced seismicity: Correlation and proposed mechanism

• DOI: 10.1016/j.epsl.2017.11.037
• Publication Date: 2017-11-27T19:46:26Z
• Authors: Michael Cardiff; David D. Lim; Jeremy R. Patterson; John Akerley; Paul Spielman; Janice Lopeman; Patrick Walsh; Ankit Singh; William Foxall; Herbert F. Wang; Neal E. Lord; Clifford H. Thurber; Dante Fratta; Robert J. Mellors; Nicholas C. Davatzes; Kurt L. Feigl
• Keywords: Geochemistry & Geophysics; 550; effective stress; 500; Geology; 01 natural sciences; Physical sciences; Earth sciences; Geophysics; geothermal field; 13. Climate action; correlation; Physical Sciences; Earth Sciences; microseismicity; 0105 earth and related environmental sciences

Abstract At Brady Hot Springs, a geothermal field in Nevada, heated fluids have been extracted, cooled, and re-injected to produce electrical power since 1992. Analysis of daily pumping records and catalogs of microseismicity between 2010 and 2015 indicates a statistically significant correlation between days when the daily volume of production was at or above its long-term average rate and days when no seismic event was detected. Conversely, shutdowns in pumping for plant maintenance correlate with increased microseismicity. We hypothesize that the effective stress in the subsurface has adapted to the long-term normal operations (deep extraction) at the site. Under this hypothesis, extraction of fluids inhibits fault slip by increasing the effective stress on faults; in contrast, brief pumping cessations represent times when effective stress is decreased below its long-term average, increasing the likelihood of microseismicity.