Parkfield earthquake

Geologists who hoped to study what happens before a quake, and in particular any signs that might enable them to predict future earthquakes, installed an elaborate array of seismometers, creepmeters, strainmeters, and other instruments in and around Parkfield starting in 1985.

Scientists with the USGS and UC Berkeley had predicted, with a 90 to 95% confidence level, that an earthquake would strike the Parkfield area between 1985 and 1993.

In June 2004, the USGS in partnership with the National Science Foundation began drilling a deep hole to house instruments to monitor the fault at depth.

Past earthquakes have also occurred to the east of Parkfield at about the same distance from the San Andreas fault near Coalinga and Avenal.

In December 2004, seismologists at the University of California, Berkeley announced the discovery of subtle tremors near Cholame, a hamlet near the San Andreas fault directly south of Coalinga.

Activity snapshot 35 hours after Sept 28, 2004 large earthquake.
Predicting the 2004 event for 1993
Aftershocks (October 11, 2004) note Paso Robles sympathetic events. ( Cholame is located near the southernmost yellow square on the eastern side of the San Andreas fault extending south-southeast from Parkfield)