Friday, July 9, 2010

California earthquake

Earthquakes in California are common occurrences as the state is located on the San Andreas Fault, which cuts across California and forms the tectonic boundary between the Pacific and the North American Plate. There are many thousands of small earthquakes per year, most of them are so small that they are not felt. California's complex and interesting landscape can be attributed to the network of faulting that runs underneath the state. The earliest reported earthquake in California was felt in 1769 by the Portola expedition about 30 miles southeast of Los Angeles, probably near the San Andreas Fault

California has hundreds of active faults located throughout the state that are capable of producing large earthquakes. The most active fault is the San Jacinto Fault in Southern California, which has produced large events on a regular basis throughout recent history. The Mendocino Triple Junction located offshore of Northern California is also very active, producing several earthquakes above magnitude 7 throughout history. Northern California is also subject to megathrust earthquakes on the Cascadia subduction zone (extending north from Mendocino), such as the 1700 Cascadia earthquake, magnitude of approximately 9. The town of Parkfield in central California is located on a section of the San Andreas Fault that produces an earthquake of about magnitude 6 every 20-30 years on average in 1857, 1881, 1901, 1922, 1934, 1966 and 2004.

The largest recorded earthquake in California was the 1857 Fort Tejon earthquake, with an estimated magnitude of 8.0. This earthquake ruptured the San Andreas Fault from Parkfield to Wrightwood, a distance of 225 miles (350 km). The most destructive earthquake to date was the 7.9 magnitude 1906 San Francisco earthquake, in which over 3000 people perished in the earthquake and the fires that followed. The 1906 quake ruptured the northern segment of the San Andreas Fault for 296 miles (477 km), from San Juan Bautista to near Cape Mendocino in the north.More recently, the 1989 Loma Prieta earthquake, which affected the San Francisco bay area, and the 1994 Northridge earthquake which hit the Greater Los Angeles area, caused widespread damage and deaths in their respective regions.

The Northridge earthquake
The Northridge earthquake occurred on January 17, 1994 at 4:31 AM Pacific Standard Time in Northridge, a neighborhood in the city of Los Angeles, California, lasting for about 45 seconds. This was a holiday Monday - Martin Luther King, Jr. Day. The earthquake had a "strong" moment magnitude of 6.7, but the ground acceleration was one of the highest ever instrumentally recorded in an urban area in North America. Seventy-two deaths were attributed to the earthquake, with over 9,000 injured. In addition, the earthquake caused an estimated $20 billion in damage, making it one of the costliest natural disasters in U.S. history.

(source: wikipedia)

Jul 8th, 2010

Yesterday, the U.S. Geological Survey said that a 5.4-magnitude earthquake jolted Southern California, jangling buildings in downtown Los Angeles, tumbling wine bottles at desert resorts and briefly halting rides at Disneyland. The temblor centered about 60 miles northeast of San Diego, it was first reported by USGS to be at 5.7 magnitudes but the agency later demoted it to 5.4.

The town nearby to the quake was Borrego Springs, situated in San Diego County. No major incidents reported on the neighboring Riverside County and there were no pressing reports of damages or injuries occurred during the quake, although residents across a spacious swath of Southern California were spooked by the force of the magnitude.

According to the U.S. Geological Survey it was about 130 miles east of Los Angeles at 4:53pm or was centered 28 miles south of Palm Springs. There were several succeeding aftershocks have been documented and with the largest measuring magnitude-3.0.


The 5.4-magnitude earthquake rattled buildings in downtown Los Angeles Wednesday, toppled wine bottles at desert resorts and briefly halted rides at Disneyland.

Researchers said it was centered 28 miles (45 kilometers) south of Palm Springs and was related to the powerful Easter Day quake, but was not an aftershock.

California Institute of Technology Seismologist Kate Hutton said the 7.2-magnitude quake in April transferred stress to fault zones farther north, triggering the quake that was felt from San Diego to Los Angeles to Las Vegas on Wednesday afternoon.

World of Color at Disney's California Adventure Park goes dark after earthquake
July 8, 2010

World of Color, the newest attraction at Disney's California Adventure Park, temporarily shut down Wednesday night, only hours after a moderate earthquake struck the region.

Still, Disney officials said it was unclear if the earthquake played a role in the "technical difficulties" that forced the cancellation of the three nightly shows.

World of Color, a water, light and fire show that erupts from the Paradise Bay Lagoon, debuted June 11.

Al Lutz, author of the Disney fan site, said the show was canceled because platforms that raise out of the water were damaged. He said divers and engineers were brought in to assess the damage.

It was unclear Thursday morning if the repairs would be made in time for the show to reopen again Thursday night.

Wednesday's 5.4-magnitude quake struck at 4:53 p.m. about 28 miles south of Palm Springs.

The cancellation of World of Color marks the second time that the show was put on hold.


Related article:

1. List of California Earthquake,

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