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Spatial decorrelation of tidal triggering and remote triggering at the Coso geothermal field

Wei Wang, Peter M. Shearer, & Xiaohua Xu

Submitted August 6, 2019, SCEC Contribution #9350, 2019 SCEC Annual Meeting Poster #080

The triggering response of seismic fault systems to short- to mid-term (i.e., seconds to months) stress fluctuations can improve our understanding of earthquake nucleation, rupture failure processes, and local stress states. Geothermal fields are well known to be susceptible to triggering effects, since the injection and extraction activities change the local stress and fluid flow conditions within geothermal areas. Here, we examine two often-studied triggering responses at very different time scales: tidal triggering by Earth tides (day to month) and remote triggering by seismic waves (seconds), within the Coso geothermal field and its vicinity. Considering that the triggered earthquakes are typically small, we take the advantage of the new quake template matching catalog in southern California, which has nearly two times more events in the Coso region and is complete to about magnitude 0.3, to examine the tidal and remote triggering. We observe strong tidal triggering of earthquakes, but no remote triggering, within the Coso geothermal field (CGF), even though the fluctuations of tidal stresses are significantly smaller than those of the passing seismic waves. The preferentially tidal triggered earthquakes occur near the time of the maximum extensional tidal strain. A possible physical mechanism to interpret these two different triggering responses is a fluid unclogging fracture process sensitive to long-period strain/stress changes.

Key Words
Tidal triggering, remote triggering

Wang, W., Shearer, P. M., & Xu, X. (2019, 08). Spatial decorrelation of tidal triggering and remote triggering at the Coso geothermal field. Poster Presentation at 2019 SCEC Annual Meeting.

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