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Anthropogenic Seismicity Rates and Operational Parameters at the Salton Sea Geothermal Field

Emily E. Brodsky, & Lia J. Lajoie

Published August 1, 2013, SCEC Contribution #1939

Geothermal power is generated at several major volcanic fields in California. As efforts to monitor seismicity increase, methods to understand the anthropogenic component need to improve. Ideally, induced earthquake rate should be forecast based on publicly-reported volumes of fluid injection or other operational parameters. At the flash facilities in the Salton Sea Geothermal Field, the total volume of fluid extracted or injected tracks the long-term evolution of seismicity. However, for recent years net fluid volume (extracted-injected) is better correlated with seismicity. After correcting for the variable aftershock rate using an Epidemic-Type Aftershock Sequence model (ETAS), we fit the background earthquake rate with a linear combination of injection and net production rate that allows us to track the secular evolution of the field. The number of earthquakes per fluid volume injected decreases gradually over time. In the Salton Sea Geothermal Field, the new analysis of induced seismicity provides a template for future evaluation of hazard directly based on measureable, controllable operational quantities. The interactions of these anthropogenic events with the larger-scale tectonic and volcanic systems remains to be investigated.

Brodsky, E. E., & Lajoie, L. J. (2013). Anthropogenic Seismicity Rates and Operational Parameters at the Salton Sea Geothermal Field. Science, 341(6145), 543-546. doi: 10.1126/science.1239213.

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Earthquake Forecasting and Predictability