Saturday, November 20, 2010

California Earthquake History & Supplies

California Earthquake History

The first strong earthquake listed in earthquake annals for California occurred in the Los Angeles region in 1769, probably near the San Andreas Fault. Four violent shocks were recorded by the Gaspar de Portola Expedition, in camp about 30 miles southeast of Los Angeles center. Most authorities speculate, even though the record is very incomplete, that this was a major earthquake.
Forty persons attending church at San Juan Capistrano on December 8, 1812, were killed by a strong earthquake that destroyed the church. Many mission buildings were severely damaged there and at San Gabriel. The shock probably centered on a submarine fault offshore.
A violent shock near Fort Tejon in January 1857 threw down buildings and large trees at the Fort. It was also severe in Los Angeles, San Francisco, and Sacramento. This earthquake has been compared to that of April 1906; both caused extensive displacement along the San Andreas Fault. One source notes, "The magnitude of the two events cannot have differed greatly."
A strong earthquake occurred on the Hayward Fault, the principal active branch of the San Andreas in central California, in October 1868. Some 30 persons were killed in the region. Damage was severe at San Francisco; many buildings were wrecked at Hayward and San Leandro. Until 1906, this shock was often referred to as "the great earthquake."
An earthquake in the Sierra - Nevada Fault system in March 1872, killed 27 people at Lone Pine and destroyed 52 of 59 adobe houses. Near Owens Lake, numerous depressions formed between cracks in the earth. One area 200 to 300 feet wide sank 20 to 30 feet; several long, narrow ponds formed. Thousands of aftershocks, some severe, appear to have occurred.
Nearly all brick structures were wrecked, and many frame buildings were damaged in Vacaville by an earthquake on April 19, 1892. Damage was similar at Winters and Dixon, two small towns nearby. Ground fissures were noted in the area. The shock centered north of Santa Rosa, in the Healdsburg Fault area.
On Christmas Day of 1899, six persons died and several were injured at Saboba, near San Jacinto, by a strong shock. At nearby Hemet, nearly all brick buildings were severely damaged, with only two chimneys remaining upright. This shock occurred on the San Jacinto Fault, and has been compared to the April 1918 (magnitude 6.8) shock in the same region.
Seven hundred persons died on April 18, 1906, in one of the greatest earthquakes ever to hit California. Damage was extensive in San Francisco, and was increased perhaps tenfold by raging fires. Total damage was estimated at over $500 million.
Two destructive shocks nearly one hour apart caused about $1 million property damage in southern Imperial Valley on June 22, 1915. Six persons were killed and several injured by the second quake at Mexicali, located just inside the Mexican border. Unstable banks of the New and Alamo Rivers caved in many places. Magnitude 6 1/4, both shocks.
A shock on the San Jacinto Fault in April 1918 caused heavy damage at San Jacinto and Hemet. Only one new concrete and one frame building remained standing in the business section of San Jacinto; property loss was about $200,000. The dry earth surface was broken up, as though by a harrow, in the San Jacinto Fault area southeast of Hemet. One auto was carried off the road by a slide; many area roads were blocked. Magnitude 6.8.
Santa Barbara sustained $8 million damage and 13 fatalities from an offshore shock in June 1925. The shock occurred in the Santa Barbara Channel, on an extension of the Mesa Fault or the Santa Ynez system. On State Street, the principal business thoroughfare, few buildings escaped damage; several collapsed. One on marshy ground withstood the shaking well, but its foundation sank 19 feet. The shock occurred at 6:42 a.m., before many people had reported for work and when streets were uncrowded, reducing death and injury. Magnitude 6.3.
The shock of November 1927 wrecked chimneys at Lompoc, shifted a house on its foundation, and caused heavy earth and rockslides on steep slopes. Water spurted from the ground in places; sand craters formed.
The Long Beach earthquake of March 1933 eliminated all doubts regarding the need for earthquake resistant design for structures in California. Forty million dollars property damage resulted; 115 lives were lost. The major damage occurred in the thickly settled district from Long Beach to the industrial section south of Los Angeles, where unfavorable geological conditions (made land, water-soaked alluvium) combined with much poor structural work to increase the damage. At Long Beach, buildings collapsed, tanks fell through roofs, and houses displaced on foundations. School buildings were among those structures most generally and severely damaged. The epicenter was offshore, southeast of Long Beach, on the Newport - Inglewood Fault. Magnitude 6.3.
Nine people were killed by the May 1940 Imperial Valley earthquake. At Imperial, 80 percent of the buildings were damaged to some degree. In the business district of Brawley, all structures were damaged, and about 50 percent had to be condemned. The shock caused 40 miles of surface faulting on the Imperial Fault, part of the San Andreas system in southern California. It was the first strong test of public schools designed to be earthquake-resistive after the 1933 Long Beach quake. Fifteen such public schools in the area had no apparent damage. Total damage has been estimated at about $6 million. Magnitude 7.1.
The towns of Tehachapi and Arvin were hit severely by the July 1952 Kern County earthquake. Twelve persons died, many were injured, and $60 million property damage was sustained. Damage to well designed structures was slight, but old and poorly built buildings were cracked, and many collapsed. Reinforced tunnels with walls 18 inches thick near Bealville were cracked, twisted, and caved in; rails were shifted and bent info S-shaped curves. Near Caliente, reinforced concrete railroad tunnels were demolished. Many aftershocks occurred, three over 6 on the Richter scale. One aftershock on August 22 (magnitude 5.8) centered near Bakersfield. It took two lives and caused extensive damage to many already weakened buildings. The Kern County earthquake, the largest with an epicenter in California since 1906, originated on the White Wolf Fault.
Abridged from Earthquake Information Bulletin, Volume 3, Number 2, March - April 1971, by Carl A. von Hake. 

Most Historic California Earthquake

Fort Tejon, California
1857 01 09 16:24 UTC
Magnitude 7.9

Largest Earthquake in California

Fort Tejon, Califronia

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 and 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.

ALL of California's Historic Earthquakes

This Web site contains eyewitness accounts and historical photographs from notable damaging earthquakes that have occurred in or near Santa Barbara County, California. It also contains a catalog of all earthquakes that have been felt in the greater Santa Barbara region between 1800 and 1960.

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