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NR 2007-01
January 3, 2007

Contact: Ed Wilson
Don Drysdale
Carrie Reinsimar
(916) 323-1886

150th ANNIVERSARY OF `BIG ONE’
A TIME TO THINK ABOUT BEING PREPARED

SACRAMENTO -- Most people know all about the largest earthquake in California’s recorded history: San Francisco destroyed by the “Big One” and ensuing fire, 3,000 dead, half a billion in damage in 1906 dollars … right?

Perhaps. Some scientists would argue that the “Biggest One” occurred about 50 years earlier, but because it didn’t have nearly the human impact as the San Francisco quake, it has been largely forgotten.

The 150th anniversary of the Great 1857 Fort Tejon earthquake is January 9. Estimated to have been a magnitude 7.9 on the San Andreas Fault, the temblor caused damage from Monterey to San Bernardino County. It was felt as far north as Marysville, as far south as San Diego and as far east as Las Vegas. But because it was centered in a sparsely populated area – the entire population of California was only about 350,000 at the time -- it only directly caused one death; a woman in Gorman was killed when an adobe house collapsed.

Not only is the earthquake often overlooked, but it’s probably misnamed. The epicenter, most scientists agree, was somewhere near the isolated southeast Monterey County community of Parkfield, not at Fort Tejon, which is on “the Grapevine” in Kern County. It is known as the Fort Tejon quake because that was the largest settlement impacted by the shaking. Two buildings were declared unsafe at the fort, which is about 4½ miles from the fault, and three others were damaged extensively.

“Although there were some rudimentary seismic instruments at a few institutions in Europe, there was no accepted universal scale by which to measure how large either the Fort Tejon or 1906 San Francisco earthquakes were, so there’s no definitive answer to the question of which was larger,” said State Geologist Dr. John Parrish, head of the California Geological Survey (CGS).

“While size does matter in an earthquake, location is equally important. A magnitude 6 earthquake directly under a city is a lot more significant than a magnitude 7 -- which releases 32 times as much energy -- in the middle of the sparsely populated desert. We know that the Fort Tejon earthquake was very large because it left a trace at the surface 225 miles long and caused the surface of the earth to

shift along the fault about 30 feet. But because it didn’t impact a major population center, it isn’t nearly as well remembered as the 1906 earthquake.”

However, Parrish noted, the anniversary should serve as a reminder to California residents to be ready for large, damaging earthquakes and other natural disasters. The basics of how to be prepared and what to do if an earthquake occurs can be found on the California Department of Conservation Web site here

“History tells us that at some point in the coming decades there likely will be very large earthquakes along the San Andreas Fault,” Parrish said, adding that the recurrence rate for a Fort Tejon-like earthquake is about 200 years. “We can’t predict earthquakes and we can’t stop them; we can only prepare to survive them. Communities and cultures that recognize the geologic hazards that surround them and learn to prepare survive natural disasters. For an example of those who don’t, visit Pompeii.”

The shaking caused by the Fort Tejon quake reportedly lasted for more than a minute and perhaps as long as two minutes. It temporarily changed the direction of the Kern River’s flow, stranded fish far from the banks of the now-vanished Tulare Lake, and sloshed water out of the Mokelumne and Los Angeles rivers. It caused some artesian wells in the Santa Clara Valley to go dry and formed new springs near Santa Barbara and San Fernando. The ground shaking partially collapsed the church tower at the old Spanish mission in Ventura. There was a report of trees sinking into the ground – possibly due to liquefaction – between Stockton and Sacramento.

A repeat of the Great 1857 Fort Tejon Earthquake today would cause significant loss of life, and damage in the billions of dollars. Wrightwood, Palmdale, Frazier Park, Taft, and other communities that didn’t exist or had tiny populations in 1857 are on or near the trace of the rupture of the Fort Tejon quake. The U. S. Interstate 5 highway -- the main land route between Northern and Southern California -- runs right by the fort, now a state historic park. While Interstate 5 crosses the San Andreas Fault only once, branches of the California Aqueduct System carrying water from Northern to Southern California cross it at several junctures.

“When people think of the `Big One’ in Southern California, this is the earthquake they’re talking about,” said Dr. Michael Reichle, Chief Seismologist for CGS. “The San Andreas Fault trends to the east and north of Los Angeles. While it’s unclear how the shaking would impact the very tall buildings in L.A., the real damage in a repeat of the Fort Tejon earthquake most likely would occur in the Inland Empire. The fault runs right through Palmdale and near San Bernardino, for example.

“In Los Angeles, I’d be more concerned about a significant earthquake on the Newport-Inglewood or Puente Hills faults than on the San Andreas, although a big quake on the San Andreas near the Salton Sea area could channel quite a bit of energy into the L.A. Basin.”

Since the 1933 Long Beach earthquake, the State of California has developed codes and regulations to build safer structures. CGS, part of the California Department of Conservation, is involved in a variety of earthquake safety-related projects. These involve research, mapping and monitoring. CGS employs geologists, seismologists and other Earth scientists, and is one of the oldest geological surveys in the United States.

In addition to mapping and studying earthquakes and other geologic phenomena, the Department of Conservation classifies areas containing mineral deposits; ensures reclamation of land used for mining; regulates oil, gas and geothermal wells; promotes beverage container recycling; and administers agricultural and open-space land conservation programs.


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