Earthquakes and groundwater

As part of the U.S Geological Survey prediction experiment at Parkfield along the San Andreas fault in California, a network of water wells is being monitored. this network consists of wells that are situated at seven sites that were drilled by Geological Survey for the express prupose of monitoring water levels. These wells have turned out to be very sensitive volume strain meters. The scientific rationale for the wells as strain meters is explained in some detail below.