Research at Parkfield

Further south in central California is the small town of Parkfield, California, which lies along the San Andreas Fault. Seismologists discovered that this section of the fault consistently produces magnitude 6.0 earthquakes about every 22 years. Following earthquakes in 1857, 1881, 1901, 1922, 1934, and 1966, scientists predicted an earthquake to hit Parkfield in 1993. This quake eventually struck in 2004 (see Parkfield earthquake). Because of this frequent activity and prediction, Parkfield has become one of the most popular spots in the world to try to capture and record large earthquakes.

In 2004, work began just north of Parkfield on the San Andreas Fault Observatory at Depth (SAFOD). The goal of SAFOD is to drill a hole nearly 3 kilometers into the Earth's crust and into the San Andreas Fault. An array of sensors will be installed to capture and record earthquakes that happen near this area.[2]

[edit] The University of California study on "the next big one"

A study completed by Yuri Fialko[3] has demonstrated that the San Andreas fault has been stressed to a level sufficient for the next "big one," as it is commonly called, that is, an earthquake of magnitude 7.0 or greater. The study also concluded that the risk of a large earthquake may be increasing faster than researchers had previously believed. Fialko also emphasized in his study that, while the San Andreas Fault has experienced massive earthquakes in 1857 at its central section and in 1906 at its northern segment (the great San Francisco earthquake), the southern section of the fault has not seen a similar rupture in at least 300 years.

If such an earthquake were to occur, Fialko's study stated, it would result in substantial damage to Palm Springs and a number of other cities in San Bernardino, Riverside and Imperial counties in California, and Mexicali municipality in Baja California. Such an event would be felt throughout much of Southern California, including densely populated areas of metropolitan Los Angeles, Orange County, San Diego and Tijuana, Baja California.

"The information available suggests that the fault is ready for the next big earthquake but exactly when the triggering will happen and when the earthquake will occur we cannot tell," Fialko said. "It could be tomorrow or it could be 10 years or more from now," he concluded in September of 2005.

[edit] The Cascadia Connection

Recent studies of past earthquake traces on both the northern San Andreas Fault and the southern Cascadia subduction zone indicate a correlation in time which may be evidence that quakes on the Cascadia subduction zone may have triggered most of the major quakes on the northern San Andreas during at least the past 3,000 years or so. The evidence also shows the rupture direction going from north to south in each of these time-correlated events. The 1906 San Francisco Earthquake seems to have been a major exception to this correlation, however, as it was not preceded by a major Cascadia quake, and the rupture moved mostly from south to north. [4]

[edit] Notable earthquakes

The San Andreas Fault has had some notable earthquakes in historic times:

  • 1857 Fort Tejon earthquake — 350 kilometers were ruptured in central and southern California. Though it is known as the Fort Tejon earthquake, the epicenter is thought to have been located far to the north, just south of Parkfield. Only two deaths were reported. The magnitude was about 8.0
  • 1906 San Francisco Earthquake — 430 kilometers were ruptured in Northern California. The epicenter was near San Francisco. About 3000 people died in the earthquake and subsequent fires. This time the magnitude was estimated to be 7.8.
  • 1989 Loma Prieta earthquake — 40 kilometers were ruptured (although the rupture did not reach the surface) near Santa Cruz, California, causing 63 deaths and moderate damage in certain vulnerable locations in the San Francisco Bay Area. Magnitude this time was about 7.1. The earthquake also postponed game 3 of the 1989 World Series at Candlestick Park.
  • 2004 Parkfield earthquake — on 28 September 2004 at quarter past 10 in the morning, a magnitude 6.0 earthquake struck California on the San Andreas Fault. This earthquake was originally expected in 1993 based on the latest earthquake prediction theories of the time. Eleven years passed before this prediction finally came to pass. Despite the extra time between events the magnitude of the earthquake was no larger than originally expected.



Copyright © 2006-17 Claud "Sonny" Rouch, all rights reserved. Website by OACYS Technology. Cover photo by Roberts Engineering.