Sooner or later southern California will get hit by a massive damaging earthquake. It will not only kill people in the initial event but also so damage infrastructure that electric power, natural gas, water, and other basic utilities will be knocked out for extended lengths of time. Water will be disrupted for weeks to months in some areas with other utility disruptions as well. The vast majority of SoCal residents will survive the big one. But then migrations will occur away from places that lose the ability to support high density populations. With all this in mind new research shows that a section of the San Andreas fault in San Luis Obispo County goes off at about 137 year intervals and it is overdue for another big one.
The Carrizo Plain section of the San Andreas has not seen a massive quake since the much-researched Fort Tejon temblor of 1857, which at an estimated magnitude of 7.9 is considered the most powerful earthquake to hit Southern California in modern times.
But the new research by UC Irvine scientists, to be published next week, found that major quakes occurred there roughly every 137 years over the last 700 years. Until now, scientists believed big quakes occurred along the fault roughly every 200 years.
We were due for another quake in that area starting around 1994. This discovery is made possible by advances in dating methods.
They went back to her archive, and the redating effort, led by scholar Sinan Akciz, found that the four big earthquakes before the 1857 temblor probably occurred around 1310, 1393, 1585 and 1640.
The Carrizo Plain is near the southern end of the San Joaquin valley about 100 miles from Los Angeles. As you can see from this map the towns of California Valley, Simmler, McKittrick, Taft, Maricopa, and New Cuyama will be especially hard hit next time this fault rips.
On January 9, 1857 at 8:20 am, an earthquake with a estimated magnitude of 8.0 occurred just north of Carrizo Plain. This quake caused nearly 30 feet (9 m) of lateral offset within Carrizo Plain, and ruptured the surface along the trace of the fault for about 220 miles (350 km). It was one of the greatest earthquakes ever recorded in the United States. Buildings in Los Angeles were severely shaken, and the quake was felt from felt from Marysville south to San Diego and east to Las Vegas, Nevada. The current of the Kern River was turned upstream, and water ran four feet deep over its banks. The waters of Tulare Lake were thrown upon its shores, stranding fish miles from the original lake bed. The waters of the Mokelumne River were thrown upon its banks, reportedly leaving the bed dry in places. The Los Angeles River was reportedly flung out of its bed, too.
I live even closer to this fault (maybe 70 miles) than the people of LA do. Bakersfield is even closer at about only 40 miles away. People in SoCal ought to read a good earthquake preparedness guide such as this preparedness guide by the LA Fire Department. Note that they say "Water is the most important item to store". Got 5 gallons stored per person in your residence? If not, you have a problem come the Big One.
Some of you out in the middle of the United States might be thinking "Oh, those crazy Californians, the dangers they choose to live with". Think again. The border of Arkansas, Missouri, Illinois, Kentucky, and Tennessee is one of the highest earthquake hazard risk zones. A repeat of the three magnitude 8 (yes, 3 of them!) 1811 and 1812 New Madrid earthquakes would devastate much of the surrounding region and cause damage in very distant places. The 1811 New Madrid quake rang church bells in Boston.
Earthquakes in the central or eastern United States affect much larger areas than earthquakes of similar magnitude in the western United States. For example, the San Francisco, California, earthquake of 1906 (magnitude 7.8) was felt 350 miles away in the middle of Nevada, whereas the New Madrid earthquake of December 1811 (magnitude 8.0) rang church bells in Boston, Massachusetts, 1,000 miles away. Differences in geology east and west of the Rocky Mountains cause this strong contrast.
|Share |||Randall Parker, 2009 January 25 10:25 AM Dangers Natural Geological|