Some induced seismicity considerations in geo-energy resource development

It is now well established that past and current geo-energy resource recovery operations associated with geothermal systems, oil and natural gas recovery operations, and long-term underground storage of waste fluids can induce earthquakes, some having magnitudes as great as 5-6. Injection into or removal of fluids from existing faults and highly stressed rocks associated with energy resource recovery and waste fluid disposal can generate the stress changes needed for fault rupture and slip along the fault plane. Important aspects of the present state of knowledge of induced seismicity, including causal mechanisms, characteristics of different energy technologies, hydraulic fracturing and waste disposal injection wells, carbon capture and storage, and assessing and managing the hazards and risks from induced seismicity are summarized in this paper. Induced earthquakes occur at shallower depths than natural tectonic earthquakes, and for a given magnitude event, shaking intensity is more severe in the epicentral region of an induced earthquake but dissipates more rapidly with distance than for a natural earthquake. In general, the greater the imbalance between the extraction and injection volumes at a site, the larger the magnitude of an observed induced earthquake. The likelihood of shaking of a given intensity at a given location can change with time for anthropogenic events in response to variations in source locations and fluid injection and withdrawal rates and volumes. Methods to account for these variations in seismic hazard and risk assessment are under development. (C) 2017 Elsevier Ltd. All rights reserved.