San Gabriel Fault
Encyclopedia
Los Angeles County, California
Los Angeles County is a county in the U.S. state of California. As of 2010 U.S. Census, the county had a population of 9,818,605, making it the most populous county in the United States. Los Angeles County alone is more populous than 42 individual U.S. states...
, running about 87 miles (140 km) southeastward from the Ridge Basin in the Sierra Pelona
Sierra Pelona Mountains
The Sierra Pelona Mountains , or the Sierra Pelona Ridge, is a mountain range in the Transverse Ranges of Southern California.. They are located within Los Angeles and Kern Counties.-Geography:...
-San Emigdio Mountains
San Emigdio Mountains
The San Emigdio Mountains are a part of the Transverse Ranges in Southern California, extending from Interstate 5 at Lebec and Gorman on the east to Highway 33–166 on the west. They link the Tehachapis and Temblor Range and form the southern wall of the San Joaquin Valley.The range is within Los...
juncture area to the western San Gabriel Mountains
San Gabriel Mountains
The San Gabriel Mountains Range is located in northern Los Angeles County and western San Bernardino County, California, United States. The mountain range lies between the Los Angeles Basin and the Mojave Desert, with Interstate 5 to the west and Interstate 15 to the east...
that forms their southwestern face near Sunland and the northeastern San Fernando Valley
San Fernando Valley
The San Fernando Valley is an urbanized valley located in the Los Angeles metropolitan area of southern California, United States, defined by the dramatic mountains of the Transverse Ranges circling it...
, and then on the south flank to the southeastern part of the San Gabriel range.
Geology
The San Gabriel Fault is a right-lateral strike-slip that was last active 1,000s of years ago — Late Quaternary west of intersection with the Sierra Madre fault, and QuaternaryQuaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
east of that intersection, and Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
only further west between Saugus and Castaic
Castaic, California
Castaic, California, is an unincorporated community and census-designated place in Los Angeles County, California, north of Santa Clarita and a few miles from Six Flags Magic Mountain amusement park. It is approximately 39 miles from the downtown Los Angeles Civic Center. As of the 2010...
-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....
.
The San Gabriel Fault was once part of the San Andreas Fault
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...
, and is believed to be the former path of it. It is also believed that the northwestern end of this fault zone meets the current San Andreas Fault zone beneath the Frazier Mountain Thrust, near the juncture of the San Andreas with the Garlock Fault
Garlock Fault
The Garlock Fault is a left-lateral strike-slip fault running approximately northeast-southwest in the Mojave Desert of southern California. It runs for much of its length along the southern base of the Tehachapi Mountains...
and Big Pine Fault.
Seismic activity
The San Gabriel Fault moves at a rate of between 1 and 5 millimeters a year, with an average slip of around 3 millimeters.See also
- 1971 San Fernando earthquake - adjacent San Fernando fault zone
- Richter scaleRichter magnitude scaleThe expression Richter magnitude scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake....
- SeismologySeismologySeismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...
- Seismic retrofitSeismic retrofitSeismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent experiences with large earthquakes near urban centers,...