| Date/Time: | January 9, 1857 about 8:20am PST |
|---|---|
| Magnitude: | Mw 7.9* |
| Location/Depth: | 35.72N 120.32W |
| Descriptive location: | 45 miles NE of San Luis Obispo |
| Faulting type: | right-lateral strike-slip |
| Faults involved: | San Andreas Fault |
| Length of surface rupture: | about 225 miles (360 km) |
| Maximum surface offset: | about 30 ft (9 meters) |
*Kerry Sieh
This earthquake occurred on the San Andreas fault, which ruptured from near Parkfield (in the Cholame Valley) almost to Wrightwood (a distance of about 300 kilometers); horizontal displacement of as much as 9 meters was observed on the Carrizo Plain. It caused one fatality. A comparison of this shock to the San Francisco earthquake, which occurred on the San Andreas fault on April 18, 1906, shows that the fault break in 1906 was longer but that the maximum and average displacements in 1857 were larger.
Property loss was heavy at Fort Tejon, an Army post about 7 kilometers from the San Andreas fault. Two buildings were declared unsafe, three others were damaged extensively but were habitable, and still others sustained moderate damage. About 20 kilometers west of Fort Tejon, trees were uprooted, and buildings were destroyed between Fort Tejon and Elizabeth Lake. One person was killed in the collapse of an adobe house at Gorman. Strong shaking lasted from 1 to 3 minutes.
Instances of seiching, fissuring, sandblows andå hydrologic changes were reported from Sacramento to the Colorado River delta. Ground fissures were observed in the beds of the Los Angeles, Santa Ana, and Santa Clara Rivers and at Santa Barbara. Sandblows occurred at Santa Barbara and in the flood plain of the Santa Clara River. One report describes sunken trees, possibly associated with liquefaction, in the area between Stockton and Sacramento.
Changes in the flow of streams or springs were observed in the areas of San Diego, Santa Barbara, Isabella, and at the south end of San Joaquin Valley. The waters of the Kern, Lake, Los Angeles, and Mokulumme Rivers overflowed their banks. Changes in the flow of water in wells were reported from the Santa Clara Valley in northern California.
Felt from Marysville south to San Diego and east to Las Vegas, Nevada. Several slight to moderate foreshocks preceded the main shock by 1 to 9 hours. Many aftershocks occurred, and two (January 9 and 16) were large enough to have been widely felt.
Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.
Isoseismal Map
Isoseismals are based on intensity estimates from data.
For More Information:
- The Great 1857 "Fort Tejon" Earthquake: Shake, Rattle, and Roll! (Fort Tejon State Historic Park monthly newsletter)
- Eyewitness Accounts (California Geology)
References
- Agnew, D. and Sieh, K., 1978, A documentary study of the felt effects of the great California earthquake of 1857: Seismol. Soc. America Bull. 68, pp. 1717-1729.
- Sieh, K., 1978, Central California foreshocks of the great 1857 earthquake: Seismol. Soc. America Bull. 68, pp. 1731-1749.
- Sieh, K., 1978, Slip along the San Andreas Fault associated with the great 1857 earthquake: Seismol. Soc. America Bull. 68, pp. 1421-1428.
- Meisling, K.E. and Sieh, K., 1980, Disturbance of trees by the 1857 Fort Tejon earthquake, California: J. Geophys. Res. 85, pp. 3225-3238.
- Grant, L., and K. Sieh, 1993, Stratigraphic evidence for 7 meters of dextral slip on the San Andreas fault during the great 1857 earthquake in the Carrizo Plain: Seismol. Soc. America Bull. 83, 619-635.
| Date/Time: | January 9, 1857 about 8:20am PST |
|---|---|
| Magnitude: | Mw 7.9* |
| Location/Depth: | 35.72N 120.32W |
| Descriptive location: | 45 miles NE of San Luis Obispo |
| Faulting type: | right-lateral strike-slip |
| Faults involved: | San Andreas Fault |
| Length of surface rupture: | about 225 miles (360 km) |
| Maximum surface offset: | about 30 ft (9 meters) |
*Kerry Sieh
This earthquake occurred on the San Andreas fault, which ruptured from near Parkfield (in the Cholame Valley) almost to Wrightwood (a distance of about 300 kilometers); horizontal displacement of as much as 9 meters was observed on the Carrizo Plain. It caused one fatality. A comparison of this shock to the San Francisco earthquake, which occurred on the San Andreas fault on April 18, 1906, shows that the fault break in 1906 was longer but that the maximum and average displacements in 1857 were larger.
Property loss was heavy at Fort Tejon, an Army post about 7 kilometers from the San Andreas fault. Two buildings were declared unsafe, three others were damaged extensively but were habitable, and still others sustained moderate damage. About 20 kilometers west of Fort Tejon, trees were uprooted, and buildings were destroyed between Fort Tejon and Elizabeth Lake. One person was killed in the collapse of an adobe house at Gorman. Strong shaking lasted from 1 to 3 minutes.
Instances of seiching, fissuring, sandblows andå hydrologic changes were reported from Sacramento to the Colorado River delta. Ground fissures were observed in the beds of the Los Angeles, Santa Ana, and Santa Clara Rivers and at Santa Barbara. Sandblows occurred at Santa Barbara and in the flood plain of the Santa Clara River. One report describes sunken trees, possibly associated with liquefaction, in the area between Stockton and Sacramento.
Changes in the flow of streams or springs were observed in the areas of San Diego, Santa Barbara, Isabella, and at the south end of San Joaquin Valley. The waters of the Kern, Lake, Los Angeles, and Mokulumme Rivers overflowed their banks. Changes in the flow of water in wells were reported from the Santa Clara Valley in northern California.
Felt from Marysville south to San Diego and east to Las Vegas, Nevada. Several slight to moderate foreshocks preceded the main shock by 1 to 9 hours. Many aftershocks occurred, and two (January 9 and 16) were large enough to have been widely felt.
Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.
Isoseismal Map
Isoseismals are based on intensity estimates from data.
For More Information:
- The Great 1857 "Fort Tejon" Earthquake: Shake, Rattle, and Roll! (Fort Tejon State Historic Park monthly newsletter)
- Eyewitness Accounts (California Geology)
References
- Agnew, D. and Sieh, K., 1978, A documentary study of the felt effects of the great California earthquake of 1857: Seismol. Soc. America Bull. 68, pp. 1717-1729.
- Sieh, K., 1978, Central California foreshocks of the great 1857 earthquake: Seismol. Soc. America Bull. 68, pp. 1731-1749.
- Sieh, K., 1978, Slip along the San Andreas Fault associated with the great 1857 earthquake: Seismol. Soc. America Bull. 68, pp. 1421-1428.
- Meisling, K.E. and Sieh, K., 1980, Disturbance of trees by the 1857 Fort Tejon earthquake, California: J. Geophys. Res. 85, pp. 3225-3238.
- Grant, L., and K. Sieh, 1993, Stratigraphic evidence for 7 meters of dextral slip on the San Andreas fault during the great 1857 earthquake in the Carrizo Plain: Seismol. Soc. America Bull. 83, 619-635.