Induced Seismicity
Some induced seismicity is inevitable and expected in EGS, which involves pumping fluids at pressure to enhance or create permeability through the use of hydro-shearing techniques. In contrast to induction of tensile failure, the purpose of hydraulic fracturing used in the oil and gas industries, EGS seeks to induce relatively small shear failure of the rock's existing joint set to create an optimum reservoir for the transfer of heat from the rock to the water in order to produce steam. Seismicity events at the Geysers geothermal field in California have been strongly correlated with injection data.
The case of induced seismicity in Basel merits special mention; it led the city (which is a partner) to suspend the project and conduct a seismic hazard evaluation, which resulted in the cancellation of the project in December 2009.
Risks associated with "hydrofracturing induced seismicity are low compared to that of natural earthquakes, and can be reduced by careful management and monitoring" and "should not be regarded as an impediment to further development of the Hot Rock geothermal energy resource".
Read more about this topic: Enhanced Geothermal System
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