SCEC Award Number 17230 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Quantifying Temporal Changes in Seismicity and Seismic Velocities in Salton Sea Geothermal Field by Template Matching Method and Ambient Noise Analysis
Investigator(s)
Name Organization
Zhigang Peng Georgia Institute of Technology
Other Participants Chenyu Li (GT student)
Chenyuan Zhang (GT visitor)
one SCEC SURE intern
SCEC Priorities 1e, 3f, 5e SCEC Groups Seismology, CS, MSW
Report Due Date 03/15/2019 Date Report Submitted 05/03/2019
Project Abstract
 In this project we use waveform-based template matching technique (WMFT) and ambient noise cross-correlation method to systematically analyze the spatial-temporal evolution of seismicity and seismic velocity in the Salton Sea Geothermal Region (SSGF). With the GPU-based WMFT, we detect earthquakes 10 days before/after some regional and teleseismic earthquakes that induced relatively high dynamic stress changes in during 2007-2014, when the Calenergy Borehole Network (EN) data are open to public. Then we search for triggered seismicity in SSGF around the target earthquakes with the statistics β-value. We find possible evidence of triggered seismicity after two regional and teleseismic earthquakes. Using empirical green’s functions (EGFs) obtained from ambient-noise cross-correlations, we find clear co-seismic reduction of seismic velocity following the 2010 M7.2 El Mayor-Cucapah earthquake, and larger co-seismic changes are associated with higher frequencies. In addition, there are clear differences in velocity changes for different station-pairs. By modeling the pore-pressure change and water flow velocity and energy during 2007-2014, we find a negative correlation between co-seismic changes and water flow velocities. We suggest that persistent fluid flow of geothermal production unclogs the fracture network, resulting in a lack of co-seismic velocity changes. This is consistent with the recent observation that remote triggering of microseismicity mostly occurred outside of geothermal regions (Zhang et al., 2017). However, we were unable to observe this pattern in Salton Sea Geothermal Field following the 2010 M7.2 El Mayor-Cucapah earthquake.
Intellectual Merit This project contributes to a better understanding of spatial-temporal evolution of seismicity and seismic velocity in Salton Sea Geothermal Region, and the response it has to human activities and stress changes induced by large regional and teleseismic earthquakes.
Broader Impacts This project supported research of a female graduate student Chenyu Li starting in Fall 2017. It also supported international collaborations with Dr. Chengyuan Zhang from Institute of Rock and Soil Mechanics, Chinese Academy of Sciences (IRSM-CAS).
Exemplary Figure Figure 2. (a) Temporal evolution of seismic velocity change from different frequency bands between sta-tion pairs HAT-ENG from 2008 to 2014. (b) Modelled water flow velocity at SSGF (cm/day) right before the 2010 El Mayor-Cucapah earthquake. (c) Relationship between co-seismic drop of velocity and water flow driven by production/injection activities (from Zhang et al., 2019).