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Abstract

Induced seismicity is currently one of the main geomechanical and environmental challenges faced by the underground industry. Current efforts focus mainly on seismic monitoring and risk assessments while progress on unraveling the mechanisms that drive induced seismicity have been addressed to a lesser extent. Here we explore stability conditions for unstable slip, and potential dynamic weakening mechanisms to explain earthquake faulting in a case of injection-induced seismicity. Injection of natural gas into the Castor Underground Gas Storage, offshore Spain, which generated a ~2 bar pressure increase, induced a seismic swarm that culminated in a series of Mw~4 earthquakes, two weeks after shut in. We focus our attention on frictional weakening and on the dynamic weakening effect of shear heating-induced thermal pressurization to explain Mw >3 earthquake faulting during the Castor sequence. These new mechanisms that we explore may help improve our understanding of cases of injection-induced seismicity, in regions of low natural seismicity, where the external forcing, or amplitude of the stress perturbation is relatively small.

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/content/papers/10.3997/2214-4609.201701675
2017-06-12
2024-03-29
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http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609.201701675
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