Induced seismicity due to EGS stimulation is well known and useful: it can depict
reservoir development in space and time. The event magnitudes rarely exceed M=3.0.
Possible, even larger events due to EGS operation (for heat and/or power production)
cannot be excluded. Experience in high-enthalpy fields show that prolonged fluid
withdrawal or injection can lead to noticeable ground shaking. Examples from The
Geysers/USA, Larderello/Italy, and Berlin/El Salvador will be presented.
For new EGS sites, the monitoring of local seismicity by a suitable seismometer
array, starting well before and stimulation/production activities, is indispensable
to provide reliable base-line information on the pre-EGS situation. Besides,
technical and social issues must be carefully addressed during EGS planning and
There is a great need for specific research on possible seismic events, their causes
and implications due to EGS operation. Substantial work is presently ongoing in the
framework of the IEA Geothermal Implementing Agreement (GIA): Annex I “Environmental
Impacts of Geothermal Energy Development” / Subtask D “Seismic risk from fluid
injection into EGS” is especially devoted to corresponding activities. Some
preliminary results will be outlined. A strong link should be established and
cooperative efforts undertaken between ENGINE and the IEA GIA.