Sep 28, 2004 · The Parkfield Experiment is a comprehensive, long-term earthquake research project on the San Andreas fault. Led by the USGS and the State of California, the experiment's purpose is to better understand the physics of earthquakes - what actually happens on the fault and in the surrounding region before, during and after an earthquake.

The Parkfield section (red) is a transition zone between the creeping and southern locked section. Stippled area marks the surface rupture in the 1857 Fort Tejon earthquake.

These instruments, set 2 to 3 km beneath the Earth's surface, will form a San Andreas Fault Observatory at Depth (SAFOD). This project will directly reveal, for the first time, the physical and chemical processes controlling earthquake generation within a seismically active fault.

The June 8, 1934 Parkfield earthquake poses several curious questions. Why did the timing of the 1934 shock violate the otherwise regular intermittent spacing of 21-22 years?

The USGS has a cluster of instruments at Parkfield to measure changes prior, during and after a moderate sized (M6) earthquake. Parkfield is located on the San Andreas fault and the town is about half way between San Francisco and Los Angeles.

Significant earthquakes have occurred on the Parkfield section of the San Andreas fault at fairly regular intervals - in 1857, 1881, 1901, 1922, 1934 and 1966. The next significant earthquake was anticipated to take place within the time frame 1988 to 1993.

As part of the Parkfield Earthquake Experiment, a large number and variety of seismic instruments have been installed there, some to monitor the seismicity leading up to the next Parkfield earthquake and some to document the strong ground motion from …

The Parkfield section of the San Andreas fault is a relatively simple part of the North American-Pacific plate boundary, with no major active intersecting faults nearby.

Earthquakes on the San Andreas fault at Parkfield are observed to occur as repeat ruptures of discrete patches on the fault surface, on scales from tens of meters to tens of kilometers.

The March 10, 1922 shock is the earliest Parkfield earthquake for which seismograms exist. Surface waves from the 1922 and 1934 shocks recorded on the Bosch-Omori seismographs at Berkeley, California, located 240 kilometers northwest of Parkfield, are very similar.