The Parkfield experiment; capturing what happens in an earthquake

To better understand what happens on and near a fault before, during, and after an earthquake, the U.S. Geological Survey (USGS) and the California Geological Survey began the Parkfield Earthquake Experiment in the 1980's. Researchers from the USGS and collaborating institutions have created a dense network of instruments on the San Andreas Fault at Parkfield, California, where moderate earthquakes have occurred at fairly regular intervals. Data from these instruments are revealing the earthquake process in unprecedented detail and will aid in predicting the time and severity of future shocks. The USGS and the National Science Foundation plan to expand the Parkfield Experiment by drilling a deep borehole and installing instruments at the actual depths where earthquakes initiate, creating a San Andreas Fault Observatory at Depth.