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2008 Chino Hills earthquake

The earthquake knocked down merchandise inside buildings such as this Yorba Linda grocery store.
San DiegoLos AngelesLas Vegas
UTC time	2008-07-29 18:42:15
ISC event	12951737
USGS-ANSS	ComCat
Local date	July 29, 2008 (2008-07-29)
Local time	11:42:15 a.m. PDT
Magnitude	5.4 Mw
Depth	15.5 km (9.6 mi)
Epicenter	33°57′11″N 117°45′40″W / 33.953°N 117.761°W / 33.953; -117.761
Fault	Yorba Linda Fault
Type	Oblique-slip
Areas affected	Greater Los Angeles Southern California United States
Total damage	Limited
Max. intensity	MMI VI (Strong)
Peak acceleration	0.44 g
Peak velocity	38 cm/s
Aftershocks	~100
Casualties	8 injured

The 2008 Chino Hills earthquake occurred at 11:42:15 am PDT (18:42:15 UTC) on July 29 in Southern California. The epicenter of the magnitude 5.4 earthquake was in Chino Hills, c. 28 miles (45 km) east-southeast of downtown Los Angeles. Movement on an oblique-slip fault resulted in a maximum Mercalli intensity of VI (Strong). Though there were no deaths, eight people were injured, and 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.

Earthquake

The Chino Hills earthquake was caused by oblique-slip faulting, with components of both thrust 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 c. 15.5 kilometers (9.6 mi) deep. Initial estimations of the moderate main shock reported it as magnitude 5.8, but this was later revised to magnitude 5.4. 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 microearthquakes, all less than magnitude 3.0, occurred in Anaheim Hills, 7 miles (11 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 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

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, c. 7 miles (11 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 structural damage was reported. California Department of Transportation 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. The earthquake affected candidates who were in the first day of the three-day California Bar Exam in nearby Ontario and Los Angeles. The State Bar ultimately did not count that portion of the test for or against any attorney candidates.

Aftershocks

Approximately 100 minor aftershocks and one presumed foreshock were reported within two days after the earthquake, 27 of which occurred within an hour after the earthquake. Four aftershocks of at least magnitude 3.0 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.

Response

There was speculation that the Chino Hills earthquake may have been a foreshock 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, c. 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. then-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 November 13, 2008, increased significantly in the aftermath of the earthquake.

See also

• List of earthquakes in 2008
• List of earthquakes in California
• List of earthquakes in the United States

References

1. National Geophysical Data Center / World Data Service (NGDC/WDS) (1972), Significant Earthquake Database (Data Set), National Geophysical Data Center, NOAA, doi:10.7289/V5TD9V7K
2. "M 5.4 – 5 km S of Chino Hills, CA – Impact". United States Geological Survey.
3. ^ "M5.5 – Greater Los Angeles area, California". United States Geological Survey.
4. Robbins, Gary (July 31, 2007). "Little known Yorba Linda fault caused Tuesday's quake". The Orange County Register. Archived from the original on August 28, 2008. Retrieved August 1, 2008.
5. "Magnitude 5.5 – Greater Los Angeles Area, California". United States Geological Survey. July 29, 2008. Archived from the original on November 4, 2009. Retrieved September 1, 2010.
6. "What's Making Judge Judy Quake?". Sky News. July 30, 2008. Archived from the original on December 16, 2008. Retrieved July 30, 2008.
7. ^ Steinhauer, Jennifer (July 29, 2008). "Earthquake Rattles Southern California". The New York Times. Archived from the original on May 12, 2011. Retrieved July 29, 2008.
8. ^ Rubin, Joel; Pierson, David; Landsberg, Mitchell (July 29, 2008). "Minor damage from 5.4 quake shows California has learned its lessons". Los Angeles Times. Archived from the original on July 30, 2008. Retrieved July 29, 2008.
9. Robbins, Gary (May 24, 2008). "Third microquake shakes Anaheim Hills". The Orange County Register. Archived from the original on September 17, 2008. Retrieved July 29, 2008.
10. Robbins, Gary. "Southern California Quake Activity Continues Odd Down Turn". The Orange County Register. Archived from the original on August 28, 2008. Retrieved July 29, 2008.
11. "Strong Earthquake Hits Southern California". CBC News. July 29, 2008. Archived from the original on July 30, 2008. Retrieved July 29, 2008.
12. "Tougher codes kept quake damage down". CNN. July 30, 2008. Archived from the original on August 5, 2008. Retrieved July 30, 2008.
13. Flaccus, Gillian (July 30, 2008). "Strict building codes credited after Calif. quake". Associated Press.
14. Colker, David (July 30, 2008). "Post-quake callers overload phone systems". Los Angeles Times. Archived from the original on August 5, 2008. Retrieved August 2, 2008.
15. ^ "What's closed, delayed after the quake". Los Angeles Times. July 29, 2008. Archived from the original on August 5, 2008. Retrieved July 30, 2008.
16. ^ Irving, Doug (July 29, 2008). "O.C. Quake roundup: Disney rides down, trains disrupted, small landslide reported". The Orange County Register. Archived from the original on July 30, 2008. Retrieved July 29, 2008.
17. Fisher, Marla Jo (July 29, 2008). "College earthquake updates". The Orange County Register. Archived from the original on August 28, 2008. Retrieved August 21, 2008.
18. "5.4 earthquake strikes Los Angeles". Chicago Tribune. July 29, 2008. Archived from the original on August 10, 2008. Retrieved August 15, 2008.
19. "5.4 quake strikes near Los Angeles". United States: ABC News. July 29, 2008. Archived from the original on December 16, 2008. Retrieved July 29, 2008.
20. ^ "Expert: L.A.'s 5.4 quake 'small sample' of one to come". CNN. July 30, 2008. Archived from the original on August 5, 2008. Retrieved August 21, 2008.
21. Irving, Doug (July 29, 2008). "O.C. QUAKE ROUNDUP: Disney rides down, trains disrupted, small landslide reported". The Orange County Register. Archived from the original on July 30, 2008. Retrieved July 29, 2008.
22. "Rattled by Quake During California Bar Exam, Some Test-Takers Cry Foul". chronicle.com. August 8, 2008. Retrieved April 19, 2022.
23. ^ Pierson, David (July 31, 2008). "Will Chino Hills earthquake shake L.A. out of complacency?". Los Angeles Times. Retrieved August 2, 2008. See also: "Southern Californians Urged to Join Largest Earthquake Drill in U.S. History" (Press release). United States Geological Survey. July 30, 2008. Archived from the original on August 5, 2008. Retrieved July 30, 2008.
24. Maugh II, Thomas (July 30, 2008). "Quake originated about eight miles under Chino Hills". Los Angeles Times. Archived from the original on August 5, 2008. Retrieved July 30, 2008.
25. ^ "Earthquake List for Map Centered at 34°N, 118°W". United States Geological Survey. Archived from the original on July 9, 2008. Retrieved July 30, 2008.
26. Whitcomb, Dan (July 30, 2008). "Earthquake jolts lucky Los Angeles". Reuters. Archived from the original on March 6, 2016. Retrieved July 30, 2008. See also: Becerrea, Hector; Pierson, David (July 31, 2008). "Experts see quake as 'teachable moment'". Los Angeles Times. Retrieved August 21, 2008.
27. "Aftershock Probability Report". Southern California Seismic Network. July 29, 2008. Archived from the original on August 4, 2008. Retrieved July 30, 2008.
28. "California Has More Than 99% Chance of a Big Earthquake WIthin 30 Years, Report Shows". ScienceDaily. April 15, 2008. Archived from the original on August 5, 2008. Retrieved July 30, 2008. See also: Field, Edward; Milner, Kevin; 2007 Working Group on California Earthquake Probabilities (2008). "Forecasting California's Earthquakes—What Can We Expect in the Next 30 Years?" (PDF). USGS Fact Sheet 2008-3027. 1.0. United States Geological Survey. Retrieved July 30, 2008.{{cite journal}}: CS1 maint: numeric names: authors list (link)

Further reading

• Kusanovic, Danilo S.; Taborda, Ricardo; Asimaki, Domniki (2023). "Soil–Structure Interaction Effects on a Regional Scale through Ground-Motion Simulations and Reduced Order Models: A Case Study from the 2008 Mw 5.4 Chino Hills Mainshock". Bulletin of the Seismological Society of America. doi:10.1785/0120220241. ISSN 0037-1106.

External links

• Chino Hills earthquake on USGS
• Gliaster, Dan (August 4, 2008). "Apocalypse – but not right now. How California stays cool about the Big One". The Guardian. Retrieved March 24, 2009.

• Earthquakes in California
• Chino Hills (California)
• 2008 earthquakes
• 2008 natural disasters in the United States
• Chino Hills, California
• 2008 in California
• July 2008 events in the United States