An analysis of earthquakes in the area around the Salton Sea Geothermal Field in southern California conducted by Emily Brodsky, a geophysicist at the University of California, Santa Cruz, has found a strong correlation between seismic activity and operations for production of geothermal power, which involve pumping water into and out of an underground reservoir. The research was published on July 11, 2013, in the journal Science.
The researchers studied earthquake records for the region from 1981 through 2012. They compared earthquake activity with production data for the geothermal power plant, including records of fluid injection and extraction. The researchers developed a statistical method to separate out the aftershocks of earthquakes allowing them to measure the activity of primary earthquakes over time.
Seismic activity was found to track well with the volume of fluid removed and reintroduced into the ground. The power plant is a “flash-steam facility” that pulls hot water out of the ground, flashes it to steam to run turbines, and recaptures as much water as possible for injection back into the ground. Due to evaporative losses, less water is pumped back in than is pulled out, so the net effect is fluid extraction.
While the largest earthquake in the region of the Salton Sea Geothermal Field during the study period was a magnitude 5.1 earthquake the proximity of four geothermal plants to the southern end of the San Andreas Fault could produce a potential for a man made earthquake on a large scale.
This is the first research that definitely proves man made earthquakes have happened.