Why do the operators of EGS activities want to avoid large Earthquakes?
In addition to the obvious reason of not wanting to create seismic hazards and community annoyances, there is also a very good engineering reason to avoid larger events. It should be pointed out that from an engineering standpoint, when one is trying to perform enhanced geothermal activities there is a target size for the volume of the subsurface permeability enhancement. In general, the geothermal operators do not want to exceed a certain radius of enhancement beyond the injection well (usually a few hundred meters) This is because to extract the maximum heat from a given volume of rock one does not want to have any “fast paths” that would “short circuit” the water, thus not allowing the injected water to heat to the desired temperature. Ideally, one wants a large matrix of many small fractures to give the maximum surface area for heating the injected water. Large long fractures will short circuit the desired paths and possibly make the EGS project les economic. Therefore, EGS operato
