Fort Tejon earthquake
Encyclopedia
The Fort Tejon earthquake occurred at about 8:20 AM (Pacific time) on January 9, 1857. It ruptured the San Andreas Fault
for a length of about 225 miles (350 kilometers), between Parkfield
and Wrightwood
. The average slip along the fault was 4.5 meters (15 feet), and a maximum offset of 9 meters (30 feet) was recorded in the Carrizo Plain
area. The amount of fault slip gives this earthquake a moment magnitude
of 7.9, comparable to that of the 1906 San Francisco earthquake
.
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Based on the (uncertain) distribution of foreshock
s for this earthquake, it is assumed that the beginning of the fault rupture (the epicenter
) was in the area between Parkfield and Cholame
, about 97 kilometres (60.3 mi) northwest. Nevertheless, it is usually called the "Fort Tejon" earthquake because this was the location of the greatest damage, most of the area being unpopulated at the time.
Only two fatalities were recorded as a result of this earthquake. One was a woman who was killed by a collapsing adobe
house at Reed's Ranch (Gorman
), very close to the fault. Most of the buildings at Fort Tejon
were badly damaged and several people were injured. Some buildings in Los Angeles
were cracked but no major damage was reported. In Ventura
the roof of Mission San Buenaventura
fell in and the bell tower was damaged. Ground cracks from liquefaction
of swampy ground were observed in Los Angeles and near Oxnard. The earthquake was felt as far south as the mouth of the Colorado River
, as far north as Marysville
and as far east as Las Vegas
.
San Andreas Fault
The San Andreas Fault is a continental strike-slip fault that runs a length of roughly through California in the United States. The fault's motion is right-lateral strike-slip...
for a length of about 225 miles (350 kilometers), between Parkfield
Parkfield, California
Parkfield is an unincorporated community in Monterey County, California. It is located on Little Cholame Creek east of Bradley, at an elevation of 1529 feet...
and Wrightwood
Wrightwood, California
Wrightwood is a census-designated place in San Bernardino County, California. It sits at an elevation of . The population was 4,525 at the 2010 census.-History:...
. The average slip along the fault was 4.5 meters (15 feet), and a maximum offset of 9 meters (30 feet) was recorded in the Carrizo Plain
Carrizo Plain
The Carrizo Plain is a large enclosed plain, approximately 50 miles long and up to 15 miles across, in southeastern San Luis Obispo County, California, about 100 miles northwest of Los Angeles, California...
area. The amount of fault slip gives this earthquake a moment magnitude
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
of 7.9, comparable to that of the 1906 San Francisco earthquake
1906 San Francisco earthquake
The San Francisco earthquake of 1906 was a major earthquake that struck San Francisco, California, and the coast of Northern California at 5:12 a.m. on Wednesday, April 18, 1906. The most widely accepted estimate for the magnitude of the earthquake is a moment magnitude of 7.9; however, other...
.
Based on the (uncertain) distribution of foreshock
Foreshock
A foreshock is an earthquake that occurs before a larger seismic event and is related to it in both time and space. The designation of an earthquake as foreshock, mainshock or aftershock is only possible after the event....
s for this earthquake, it is assumed that the beginning of the fault rupture (the epicenter
Epicenter
The epicenter or epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates...
) was in the area between Parkfield and Cholame
Cholame, California
Cholame, California is an unincorporated community in San Luis Obispo County, California, USA. It sits within a mile of the San Andreas Rift Zone fault line at an elevation of 1,157 feet above sea level and is located at . Cholame is reached via State Route 41, just southwest of the junction of...
, about 97 kilometres (60.3 mi) northwest. Nevertheless, it is usually called the "Fort Tejon" earthquake because this was the location of the greatest damage, most of the area being unpopulated at the time.
Only two fatalities were recorded as a result of this earthquake. One was a woman who was killed by a collapsing adobe
Adobe
Adobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material , which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings. Adobe structures are extremely durable, and account for...
house at Reed's Ranch (Gorman
Gorman, California
Gorman, California, is an unincorporated community in northwestern Los Angeles County. As of 2005 it had just 15 homes and a few registered voters, but tens of thousands of motorists traveled through it daily on the Interstate 5 freeway....
), very close to the fault. Most of the buildings at Fort Tejon
Fort Tejon
Fort Tejon in California is a former United States Army outpost which was intermittently active from June 24, 1854, until September 11, 1864. It is located in the Grapevine Canyon area of Tejon Pass along Interstate 5, the main route through the mountains separating the Central Valley from Los...
were badly damaged and several people were injured. Some buildings in Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
were cracked but no major damage was reported. In Ventura
Ventura, California
Ventura is the county seat of Ventura County, California, United States, incorporated in 1866. The population was 106,433 at the 2010 census, up from 100,916 at the 2000 census. Ventura is accessible via U.S...
the roof of Mission San Buenaventura
Mission San Buenaventura
Mission San Buenaventura was founded on Easter Sunday, March 31, 1782 in Las Californias, part of the Spanish Viceroyalty of New Spain. Named for a Franciscan theologian, Saint Bonaventure, it was the last of the missions founded by Father Serra...
fell in and the bell tower was damaged. Ground cracks from liquefaction
Soil liquefaction
Soil liquefaction describes a phenomenon whereby a saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid....
of swampy ground were observed in Los Angeles and near Oxnard. The earthquake was felt as far south as the mouth of the Colorado River
Colorado River
The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...
, as far north as Marysville
Marysville, California
Marysville is the county seat of Yuba County, California, United States. The population was 12,072 at the 2010 census, down from 12,268 at the 2000 census. It is included in the Yuba City Metropolitan Statistical Area, often referred to as the Yuba-Sutter Area after the two counties, Yuba and...
and as far east as Las Vegas
Las Vegas, Nevada
Las Vegas is the most populous city in the U.S. state of Nevada and is also the county seat of Clark County, Nevada. Las Vegas is an internationally renowned major resort city for gambling, shopping, and fine dining. The city bills itself as The Entertainment Capital of the World, and is famous...
.