2008 Chino Hills earthquake
Encyclopedia
The 2008 Chino Hills earthquake occurred at 11:42:15 a.m. PDT
(18:42:15 UTC
) on July 29, 2008, in Southern California
. The epicenter
of the magnitude 5.5
earthquake
was in Chino Hills
, approximately 28 miles (45.1 km) east-southeast of downtown Los Angeles
.
Though no lives were lost during the earthquake, it caused considerable damage in numerous structures throughout the area and caused some amusement park
facilities to shut down their rides. The earthquake led to increased discussion regarding the possibility of a stronger earthquake in the future.
and sinistral
strike-slip
displacement. Preliminary reports cited the Whittier fault
as the active cause, but the quake was later determined to have been generated by the "Yorba Linda trend
," as identified by Caltech
seismologist Egill Hauksson. Its epicenter
was within 3 miles (4.8 km) of Chino Hills
and its hypocenter
was approximately 9.1 miles (14.6 km) deep. Initial estimations of the moderate main shock reported it as magnitude 5.8
, but this was later revised to magnitude 5.4 and in later months to a 5.5. The main shock was reportedly felt as far south as San Diego, and Tijuana, Mexico, and as far east as Las Vegas, Nevada
. It was the strongest earthquake to occur in the greater Los Angeles area since the 1994 Northridge earthquake.
As reported by The Orange County Register
, three microquakes, all less than magnitude 3.0, occurred in Anaheim Hills, 7 miles (11.3 km) southwest of Chino Hills, two months before the Chino Hills earthquake. There was an unusually low amount of seismic activity in Southern California in the week prior to the quake. Between July 20 and July 26, 2008, there were no earthquakes in Southern California exceeding magnitude 3.0, thus there was speculation that the wane in seismic activity was a precursor to a possible larger event.
The Chino Hills earthquake caused no deaths or significant damage due to the physical location of its epicenter. Most of the infrastructure in the Chino Hills
area is relatively new and well suited to withstand a large quake. Unlike previous earthquakes in the region—such as the 1994 Northridge earthquake and the 1987 Whittier Narrows earthquake, which caused serious structural damage and fatalities—this quake caused only minor damage. However, the high volume of telephone use following the shock overloaded provider capacity and disrupted service into the afternoon.
Amusement rides at Disneyland, Six Flags Magic Mountain
, Universal Studios Hollywood
and Knott's Berry Farm
were evacuated and temporarily shut down. California State University, Fullerton
suffered some damage in its older, inadequately engineered
buildings. In Orange
, the Chapman University School of Law
was evacuated after a water pipe was ruptured. Pipes on a Macy's department store in Westfield Topanga
ruptured during the tremor flooding the store which closed for a couple of days in order to be repaired. A light fixture damaged by the shock started a small fire in the Westfield MainPlace Mall in Santa Ana
; since the fire was in an empty movie theater, nobody was harmed.
A gap was reported on California State Route 91
near Anaheim Hills, approximately 7 miles (11.3 km) southwest of the epicenter, but the California Department of Transportation
concluded that the gap did not pose a danger. A minor landslide near the freeway caused some traffic congestion, but no injuries or structural damage were reported.
Caltrans replaced an expansion joint
on an Interstate 5 truck overpass at the El Toro Y
Interchange. The roof of Placentia
's public library nearly collapsed; afterwards, the building was closed for repairs.
Electrical outages were reported in Chino
, Chino Hills
, Diamond Bar
and Pomona
. Over 2,000 people lost power after a fire broke out at a La Habra
power station, but electricity was restored that afternoon. Los Angeles International Airport
reported a ground radar system outage along with a broken water heater, causing flooding in the checked luggage preparation area of Terminal 7. Minor injuries from falling ceiling tiles were reported at a medical clinic in Brea
.
s and one presumed foreshock
were reported within two days after the Chino Hills earthquake, 27 of which occurred within an hour after the quake. Four aftershocks of at least 3.0 in magnitude were reported—the first, nine minutes following the initial earthquake, was the largest at magnitude 3.8; and two others, occurring over two hours later, were recorded at magnitude 3.6. Twenty-eight aftershocks of at least 2.0 were reported. One presumed foreshock
, magnitude 1.3, occurred sixteen hours prior to the earthquake in the same location as the main shock.
to a larger earthquake. The Southern California Seismic Network's Aftershock Probability Report, produced minutes after the event, stated that "Most likely, the recent mainshock will be the largest in the sequence. However, there is a small chance, approximately 5–10%, of an earthquake equal to or larger than this mainshock in the next 7 days."
Geologists at the United States Geological Survey
and Uniform California Earthquake Rupture Forecast suggest that an earthquake with a magnitude of 6.7 or larger will almost definitely occur somewhere in the state within the next 30 years. California Governor Arnold Schwarzenegger
said: "This earthquake reminds us to be prepared. [...] We were very fortunate that there were no serious injuries or property damage." Additionally, registration for the Great Southern California ShakeOut, a regional earthquake drill scheduled to occur on Nov. 13, 2008, increased significantly in the aftermath of the earthquake.
Pacific Time Zone
The Pacific Time Zone observes standard time by subtracting eight hours from Coordinated Universal Time . The clock time in this zone is based on the mean solar time of the 120th meridian west of the Greenwich Observatory. During daylight saving time, its time offset is UTC-7.In the United States...
(18:42:15 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
) on July 29, 2008, in Southern California
Southern California
Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...
. 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...
of the magnitude 5.5
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...
earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
was in Chino Hills
Chino Hills, California
Chino Hills is a Los Angeles suburb located in the southwestern corner of San Bernardino County, California, United States. The city borders Los Angeles County on its northwest side, Orange County to its south, and Riverside County to its southeast...
, approximately 28 miles (45.1 km) east-southeast of downtown Los Angeles
Downtown Los Angeles
Downtown Los Angeles is the central business district of Los Angeles, California, United States, located close to the geographic center of the metropolitan area...
.
Though no lives were lost during the earthquake, it caused considerable damage in numerous structures throughout the area and caused some amusement park
Amusement park
thumb|Cinderella Castle in [[Magic Kingdom]], [[Disney World]]Amusement and theme parks are terms for a group of entertainment attractions and rides and other events in a location for the enjoyment of large numbers of people...
facilities to shut down their rides. The earthquake led to increased discussion regarding the possibility of a stronger earthquake in the future.
Tectonics
The Chino Hills earthquake was caused by oblique slip faulting, with components of both thrustThrust 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...
and sinistral
Sinistral
Sinistral and dextral are scientific terms that describe chirality or relative direction in a number of disciplines.The terms are derived from the Latin words for “left” and “right” ....
strike-slip
Strike-slip tectonics
Strike-slip tectonics is concerned with the structures formed by, and the tectonic processes associated with, zones of lateral displacement within the crust or lithosphere.-Deformation styles:-Riedel shear structures:...
displacement. Preliminary reports cited 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:...
as the active cause, but the quake was later determined to have been generated by the "Yorba Linda trend
Yorba Linda Fault
The Yorba Linda Fault or Yorba Linda Trend is a Fault system that extends from North East Yorba Linda, California to the South Eastern portion of Chino Hills, California. The fault was discovered in the late 1990s and is known to have caused the MW5.4 2008 Chino Hills earthquake. The fault is...
," as identified by 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...
seismologist Egill Hauksson. Its 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 within 3 miles (4.8 km) of Chino Hills
Chino Hills, California
Chino Hills is a Los Angeles suburb located in the southwestern corner of San Bernardino County, California, United States. The city borders Los Angeles County on its northwest side, Orange County to its south, and Riverside County to its southeast...
and its hypocenter
Hypocenter
The hypocenter refers to the site of an earthquake or a nuclear explosion...
was approximately 9.1 miles (14.6 km) deep. Initial estimations of the moderate main shock reported it as magnitude 5.8
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...
, but this was later revised to magnitude 5.4 and in later months to a 5.5. The main shock was reportedly felt as far south as San Diego, and Tijuana, Mexico, and as far east as Las Vegas, Nevada
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...
. It was the strongest earthquake to occur in the greater Los Angeles area since the 1994 Northridge earthquake.
As reported by The Orange County Register
The Orange County Register
The Orange County Register is a daily newspaper published in Santa Ana, California. The Register is the flagship publication of Freedom Communications, Inc., which publishes 28 daily newspapers, 23 weekly newspapers, Coast magazine, and several related Internet sites.The Register is notable for its...
, three microquakes, all less than magnitude 3.0, occurred in Anaheim Hills, 7 miles (11.3 km) southwest of Chino Hills, two months before the Chino Hills earthquake. There was an unusually low amount of seismic activity in Southern California in the week prior to the quake. Between July 20 and July 26, 2008, there were no earthquakes in Southern California exceeding magnitude 3.0, thus there was speculation that the wane in seismic activity was a precursor to a possible larger event.
Impact
Chino Hills, California
Chino Hills is a Los Angeles suburb located in the southwestern corner of San Bernardino County, California, United States. The city borders Los Angeles County on its northwest side, Orange County to its south, and Riverside County to its southeast...
area is relatively new and well suited to withstand a large quake. Unlike previous earthquakes in the region—such as the 1994 Northridge earthquake and the 1987 Whittier Narrows earthquake, which caused serious structural damage and fatalities—this quake caused only minor damage. However, the high volume of telephone use following the shock overloaded provider capacity and disrupted service into the afternoon.
Amusement rides at Disneyland, Six Flags Magic Mountain
Six Flags Magic Mountain
Six Flags Magic Mountain is a theme park located in Valencia, California north of Los Angeles. It opened on Memorial Day weekend on May 30, 1971 as Magic Mountain, by the Newhall Land and Farming Company. In 1979, Six Flags purchased the park and added the name Six Flags to the park's title. In...
, Universal Studios Hollywood
Universal Studios Hollywood
Universal Studios Hollywood is a movie studio and theme park in the unincorporated Universal City community of Los Angeles County, California, United States. It is one of the oldest and most famous Hollywood movie studios still in use...
and Knott's Berry Farm
Knott's Berry Farm
Knott's Berry Farm is a theme park in Buena Park, California, now owned by Cedar Fair Entertainment Company, and a line of jams, jellies, preserves, and other specialty food, now part of The J. M. Smucker Company based in Placentia, California....
were evacuated and temporarily shut down. California State University, Fullerton
California State University, Fullerton
California State University, Fullerton is a public university located in Fullerton, California. It is the largest institution in the CSU System by enrollment, it offers long-distance education and adult-degree programs...
suffered some damage in its older, inadequately engineered
Earthquake engineering
Earthquake engineering is the scientific field concerned with protecting society, the natural and the man-made environment from earthquakes by limiting the seismic risk to socio-economically acceptable levels...
buildings. In Orange
Orange, California
Southern California is well-known for year-round pleasant weather: - On average, the warmest month is August. - The highest recorded temperature was in 1985. - On average, the coolest month is December. - The lowest recorded temperature was in 1950...
, the Chapman University School of Law
Chapman University School of Law
Chapman University School of Law, commonly referred to as Chapman Law or Chapman Law School, is a private, non-profit law school located in Orange, California. The school offers the Juris Doctor degree , combined programs offering a JD/MBA and JD/MFA in Film & Television Producing, and LL.M...
was evacuated after a water pipe was ruptured. Pipes on a Macy's department store in Westfield Topanga
Westfield Topanga
Westfield Topanga, formerly known as the Westfield Shoppingtown Topanga and more commonly known to locals as the Topanga Mall or Topanga Plaza, is a two-story shopping mall consisting of 230 tenants spread across three sections...
ruptured during the tremor flooding the store which closed for a couple of days in order to be repaired. A light fixture damaged by the shock started a small fire in the Westfield MainPlace Mall in Santa Ana
Santa Ana, California
Santa Ana is the county seat and second most populous city in Orange County, California, and with a population of 324,528 at the 2010 census, Santa Ana is the 57th-most populous city in the United States....
; since the fire was in an empty movie theater, nobody was harmed.
A gap was reported on California State Route 91
California State Route 91
State Route 91 is a major east–west freeway located entirely within Southern California and serving several regions of the Greater Los Angeles metropolitan area...
near Anaheim Hills, approximately 7 miles (11.3 km) southwest of the epicenter, but the California Department of Transportation
California Department of Transportation
The California Department of Transportation is a government department in the U.S. state of California. Its mission is to improve mobility across the state. It manages the state highway system and is actively involved with public transportation systems throughout the state...
concluded that the gap did not pose a danger. A minor landslide near the freeway caused some traffic congestion, but no injuries or structural damage were reported.
Caltrans replaced an expansion joint
Expansion joint
An expansion joint or movement joint is an assembly designed to safely absorb the heat-induced expansion and contraction of various construction materials, to absorb vibration, to hold certain parts together, or to allow movement due to ground settlement or earthquakes...
on an Interstate 5 truck overpass at the El Toro Y
El Toro Y
The El Toro "Y" is a freeway interchange in southern Orange County, California where the Santa Ana Freeway, Interstate 5, and the San Diego Freeway, Interstate 405 merge...
Interchange. The roof of Placentia
Placentia, California
-Local: Placentia is a Charter city with an elected city council and professional city manager. Placentia City Council*Mayor- Scott W. Nelson*Mayor Pro Tem- Jeremy Yamaguchi*Council Member- Joe Aquirre*Council Member- Constance Underhill...
's public library nearly collapsed; afterwards, the building was closed for repairs.
Chino, California
Chino is a city in San Bernardino County, California, United States. It is located in the western end of the Riverside-San Bernardino Area and it is easily accessible via the Chino Valley and Pomona freeways....
, Chino Hills
Chino Hills, California
Chino Hills is a Los Angeles suburb located in the southwestern corner of San Bernardino County, California, United States. The city borders Los Angeles County on its northwest side, Orange County to its south, and Riverside County to its southeast...
, Diamond Bar
Diamond Bar, California
Diamond Bar is a city in eastern Los Angeles County, California, United States. The population was 55,544 at the 2010 census, down from 56,287 at the 2000 census. It is named after the "diamond over a bar" branding iron registered in 1918 by ranch owner Frederick E...
and Pomona
Pomona, California
-2010:The 2010 United States Census reported that Pomona had a population of 149,058, a slight decline from the 2000 census population. The population density was 6,491.2 people per square mile...
. Over 2,000 people lost power after a fire broke out at a La Habra
La Habra, California
La Habra is a city in the northwestern corner of Orange County, California. In the 2010 census, the city had a population of 60,239. Its related city, La Habra Heights is located to the north of La Habra, and is in Los Angeles County.-Origin of name:...
power station, but electricity was restored that afternoon. Los Angeles International Airport
Los Angeles International Airport
Los Angeles International Airport is the primary airport serving the Greater Los Angeles Area, the second-most populated metropolitan area in the United States. It is most often referred to by its IATA airport code LAX, with the letters pronounced individually...
reported a ground radar system outage along with a broken water heater, causing flooding in the checked luggage preparation area of Terminal 7. Minor injuries from falling ceiling tiles were reported at a medical clinic in Brea
Brea, California
Brea is a city in Orange County, California. The population, as of the 2010 Census was 39,282.The city began as a center of crude oil production, was later propelled by citrus production, and is now an important retail center because of the large Brea Mall and the recently redeveloped Brea Downtown...
.
Aftershocks
Approximately 100 minor aftershockAftershock
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 and one presumed 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....
were reported within two days after the Chino Hills earthquake, 27 of which occurred within an hour after the quake. Four aftershocks of at least 3.0 in magnitude were reported—the first, nine minutes following the initial earthquake, was the largest at magnitude 3.8; and two others, occurring over two hours later, were recorded at magnitude 3.6. Twenty-eight aftershocks of at least 2.0 were reported. One presumed 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....
, magnitude 1.3, occurred sixteen hours prior to the earthquake in the same location as the main shock.
Response
There was speculation that the Chino Hills earthquake may have been a foreshockForeshock
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 earthquake. The Southern California Seismic Network's Aftershock Probability Report, produced minutes after the event, stated that "Most likely, the recent mainshock will be the largest in the sequence. However, there is a small chance, approximately 5–10%, of an earthquake equal to or larger than this mainshock in the next 7 days."
Geologists at the United States Geological Survey
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,...
and Uniform California Earthquake Rupture Forecast suggest that an earthquake with a magnitude of 6.7 or larger will almost definitely occur somewhere in the state within the next 30 years. California Governor Arnold Schwarzenegger
Arnold Schwarzenegger
Arnold Alois Schwarzenegger is an Austrian-American former professional bodybuilder, actor, businessman, investor, and politician. Schwarzenegger served as the 38th Governor of California from 2003 until 2011....
said: "This earthquake reminds us to be prepared. [...] We were very fortunate that there were no serious injuries or property damage." Additionally, registration for the Great Southern California ShakeOut, a regional earthquake drill scheduled to occur on Nov. 13, 2008, increased significantly in the aftermath of the earthquake.