The U.S. is conducting collaborative research under the EGS Collab project supported by the U.S. Department of Energy’s Geothermal Technologies Office to understand the fracture creation and imaging during fracturing in enhanced geothermal systems. Real-time, automatic microearthquake detection and location provides useful information on fracture growth during stimulation. We study the capability of our newly developed multiscale event scanning method for real-time microearthquake monitoring using microearthquake data acquired during the EGS Collab Experiment I. We compute correlation coefficients between STA/LTA (short-time average/long-time average) of recorded seismograms and those of pre-calculated microearthquake waveforms in a database using a moving time window, and search for the grid points with the highest correlation coefficients to detect and locate microearthquake events simultaneously. Our multiscale event scanning method requires much less computation cost than that of the global search for all grid points and every scanning time step, making real-time microearthquake detection and location feasible. We apply our method to microearthquake data acquired during the EGS Collab Experiment I. Compared to LBNL’s high-precision location results for 676 events, our method detects approximately 90% of those events with correlation coefficients greater than 0.6 and a standard deviation difference smaller than 2 m. We detect 827 MEQs and 6286 MEQs with correlation coefficients greater than 0.7 and 0.6, respectively. Our real-time MEQ detection and location results reveal the stimulation-created and possible pre-existing fractures. The average computational cost for detecting and locating one event is approximately one second. Our results demonstrate that our newly developed multiscale scanning method is capable of reliably detecting and locating MEQs in nearly real time during EGS stimulations.

Press the Back button in your browser, or search again.

Copyright 2019, Stanford Geothermal Program: Readers who download papers from this site should honor the copyright of the original authors and may not copy or distribute the work further without the permission of the original publisher.