Seismicity

The phenomenon of seismicity associated with geothermal power production has been known and acknowledged for decades. With the expanded geothermal development beginning in the in the 1970's, there was a measurable increase in the frequency of "microearthquakes", or earthquakes registering under 3.0 on the Richter scale. They are measured and located by sensitive monitoring instruments while the vast majority of the microearthquakes are not detectable by humans. The strongest of the events are felt only by people in the immediate vicinity of the epicenter and normally do not cause damage.

Both geothermal operators and the United States Geological Survey (USGS) operate earthquake monitoring networks (the USGS has not assumed management of the geothermal operator stations due to what it judges to be a low risk posed by microearthquakes). All monitoring data is made available to the public on the Northern California Earthquake Data Center website.

Since there are no mapped faults that have been active in the last 10,000 years within The Geysers, seismologists have stated there is no reason to believe there is the potential for a sizeable seismic event attributable to geothermal operations.

The Geysers, by its very nature, is one of the most dynamic and geologically active areas in the world. It has been this way for centuries and will continue to be with or without geothermal activity.