Puente Hills Fault
Encyclopedia
The Puente Hills Fault, or the Puente Hills thrust system, is a thrust fault
located across the Los Angeles Basin
, discovered in 1999. It runs about 25 miles from the Puente Hills
region in the southeast to just south of Griffith Park
, Los Angeles
in the northwest. The fault is often referred to as a blind thrust fault due to a lack of superficial ground features normally associated with thrust faults that have recently experienced seismic activity. The fault is distinct in that it runs across the Los Angeles Basin, and is separate from the Whittier Fault
.
, which is a transform fault
. More specifically, geologists have determined that the fault has ruptured at least four times in the past 11,000 years. The magnitudes of such earthquakes are considered to have been 7.0 - 7.5 Mw.
The location of the fault directly below metropolitan Los Angeles
leads it to be of great concern for the public, with various predicted scenarios in the event of an earthquake. If a similar earthquake were to happen today, the projected losses by the USGS say about "250 Billion in property damage" and 3,000-18,000 deaths would happen.
and USGS
.
According to Dr.Hutton from CALTECH
, the chance that the early morning tremor was a foreshock
to a larger quake was initially 5 percent but would rapidly decline to 1 percent after 24 hours.
The quake was slightly unusual because hours later there still had been no aftershock
s.
Thrust fault
A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...
located across the Los Angeles Basin
Los Angeles Basin
The Los Angeles Basin is the coastal sediment-filled plain located between the Peninsular and Transverse ranges in southern California in the United States containing the central part of the city of Los Angeles as well as its southern and southeastern suburbs...
, discovered in 1999. It runs about 25 miles from the Puente Hills
Puente Hills
The Puente Hills is a chain of hills, one of the lower Transverse Ranges, in an unincorporated area in eastern Los Angeles County, California.-Geography:...
region in the southeast to just south of Griffith Park
Griffith Park
Griffith Park is a large municipal park at the eastern end of the Santa Monica Mountains in the Los Feliz neighborhood of Los Angeles, California. The park covers of land, making it one of the largest urban parks in North America...
, Los Angeles
Los Angeles, California
Los Angeles , with a population at the 2010 United States Census of 3,792,621, is the most populous city in California, USA and the second most populous in the United States, after New York City. It has an area of , and is located in Southern California...
in the northwest. The fault is often referred to as a blind thrust fault due to a lack of superficial ground features normally associated with thrust faults that have recently experienced seismic activity. The fault is distinct in that it runs across the Los Angeles Basin, and is separate from the Whittier Fault
Whittier Fault
The Whittier Fault is a geologic fault located in eastern Los Angeles County in Southern California, that is one of the two upper branches of the Elsinore Fault Zone, with the Chino Fault the second.-Geology:...
.
Seismic Risk
The frequency of a major rupture in the Puente Hills Fault is on the order of once per several thousand years. This frequency of occurrence is relatively rare compared to the San Andreas FaultSan 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...
, which is a transform fault
Transform fault
A transform fault or transform boundary, also known as conservative plate boundary since these faults neither create nor destroy lithosphere, is a type of fault whose relative motion is predominantly horizontal in either sinistral or dextral direction. Furthermore, transform faults end abruptly...
. More specifically, geologists have determined that the fault has ruptured at least four times in the past 11,000 years. The magnitudes of such earthquakes are considered to have been 7.0 - 7.5 Mw.
The location of the fault directly below metropolitan 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...
leads it to be of great concern for the public, with various predicted scenarios in the event of an earthquake. If a similar earthquake were to happen today, the projected losses by the USGS say about "250 Billion in property damage" and 3,000-18,000 deaths would happen.
Pico Rivera earthquake
The 4.4 2010 Pico Rivera earthquake, at 4:04 AM on March 16, 2010, may have been caused by movement on this fault according to CALTECHCalifornia Institute of Technology
The California Institute of Technology is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering...
and USGS
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
.
According to Dr.Hutton from CALTECH
California Institute of Technology
The California Institute of Technology is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering...
, the chance that the early morning tremor was a 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....
to a larger quake was initially 5 percent but would rapidly decline to 1 percent after 24 hours.
The quake was slightly unusual because hours later there still had been no aftershock
Aftershock
An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock...
s.