SCEC Award Number 13167 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Geothermal Pumping and Seismicity in the Salton Sea Geothermal Field, CA
Investigator(s)
Name Organization
David Jackson University of California, Los Angeles
Other Participants Weiser, Deborah (UCLA GRAD STUDENT)
SCEC Priorities 2f, 2b SCEC Groups Seismology, EFP, WGCEP
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 California is home to eleven geothermal fields, some near seismically active areas. Induced seismicity has been recognized at The Geysers and Salton Sea Geothermal Fields and has likely occurred at other California fields (e.g. Brodsky and LaJoie, 2013). Our study examines the eleven California geothermal fields that have publicly available monthly injection and extraction totals from DOGGR, the Department of Oil, Gas, and Geothermal Resources. We use seismicity data from the Waveform Relocated Earthquake Catalog for Southern California (Hauksson et al., 2012), and the Double Difference Earthquake Catalog for Northern California (Waldhauser and Schaff, 2008), supplemented with Southern California Seismic Network (SCSN) data from 2011-2013 (Hutton et al., 2010). We examine fluid volume injected, fluid volume produced, their difference (net pumping), and Benioff strain with time. We used Benioff strain, proportional to the square root of seismic moment, to portray both magnitude and number of earthquakes. Many geothermal fields were already seismically active before geothermal pumping began, making it difficult to distinguish induced from natural seismicity. We found examples showing Benioff strain rate increasing when net pumping started or accelerated, decreasing when pumping ceased, increasing when fluid withdrawal accelerated, and changing for no reason clearly associated with pumping. While evidence of triggering by fluid pumping is convincing is some cases, managing earthquake risk must generally involve substantial uncertainty.
Intellectual Merit We found examples showing Benioff strain rate increasing when net pumping started or accelerated, decreasing when pumping ceased, increasing when fluid withdrawal accelerated, and changing for no reason clearly associated with pumping.
Broader Impacts Geothermal energy is an important to California and the US as a source on relatively non-polluting energy, but it also involves earthquake risk. While evidence of triggering by fluid pumping is convincing is some cases, managing earthquake risk must generally involve substantial uncertainty.
Exemplary Figure Figure 1. Fluid injection, fluid production, net pumping, and cumulative Benioff strain for the Geysers Geothermal field.