California Earthquake Consequences of a Major Earthquake

California Earthquake

Consequences of a Major Earthquake in California

On March 11, 2011 a powerful, magnitude 8.9 earthquake hit northeastern Japan, triggering a tsunami with 10-meter-high waves that reached the U.S. west coast. The earthquake was one of the five most powerful events since modern record keeping began in 1900, triggering tsunami waves of 40.5 meters (133 ft.) on Japan's coast.

One year after the event Japanese authorities reported 15,831 deaths, 6,107 injured, 3,018 missing. In all 129,225 buildings totally collapsed, 254,204 half collapsed and another 691,766 buildings partially collapsed. The earthquake and tsunami resulted in extensive damage to roads and railways; caused many fires and a dam collapse (National Police Agency of Japan, 2012). The tsunami caused a number of nuclear accidents including the ongoing level 7 meltdown at three reactors in the Fukushima Daiichi Nuclear Power Plant complex. Residents within a 20 km (12-mile) radius of the complex were evacuated.

Could a similar event occur in California?

In 2008, a multi-disciplinary collaboration of scientists and engineers released the Uniform California Earthquake Rupture Forecast (UCERF) which predicts a 99.7% likelihood of a 6.7 or larger earthquake in California in the next 30 years (Koprowski, 2010). The chances of such an event are greater in Southern California, 97% than Northern California, 93% (Chang, 2008). Since 1900 there have been 57 earthquakes of magnitude 6.5 or higher in and around California, the last being the April 4, 2010, Baja California earthquake with a magnitude of 7.2. The quake resulted in 4 deaths and 100 injuries and was felt throughout the Western United States and Northwest Mexico. It was the strongest earthquake to hit Southern California since the 1992 Landers earthquake and the 1952 Kern County earthquake. These earthquakes had similar magnitudes, and were also felt across much of western North America.

California is one of the most seismically active regions in the world. The state sits atop the confluence of two of the Earth's major tectonic plates, the Pacific and the North American. Over 300 faults crisscross the state and approximately 10,000 earthquakes occur each year, however most are too small to be felt. Scientists report that of all the faults in the state the southern part of the San Andreas Fault, which runs from Parkfield to the Salton Sea, seems most primed to rupture. There is a 59% chance in the next three decades that a Northridge-size quake (6.7 magnitude in1994)) will occur on the fault, compared to a 21% chance for the northern section (Chang, 2008).

The northern San Andreas produced the 1906 San Francisco earthquake, a recent disaster compared to the southernmost segment, which has been quiet for more than three centuries. Scientists are also concerned about the Hayward and San Jacinto faults, which each have a 31% chance of producing a Northridge-size temblor in the next 30 years. The Hayward fault runs through densely populated cities in the San Francisco Bay Area. The San Jacinto fault bisects the fast-growing city of San Bernardino.

No amount of preparation can fully protect California from the type of damage suffered in Japan. Geologists say a big earthquake in California would probably top out at a magnitude 8 as the state's fault structures are different from Japan's. A quake of the 7.8 magnitude would have about 30 times less power than the one that struck Japan. However, it is predicted 2,000 deaths and $200 billion in damage will result from a 7.8 southern California quake on the San Andreas Fault (Henderson, 2011).