The Big One may be overdue to hit California, but scientists near LA have found a new risk for the area during a major earthquake, Joinfo.com reports with reference to Mail Online.
They claim that if a major tremor hits the area, it could plunge large parts of California into the sea almost instantly.
The discovery was made after studying the Newport-Inglewood fault, which has long been believed to be one of Southern California’s danger zones.
The fault runs under densely populated areas, from the Westside of Los Angeles to the Orange County coast.
Major earthquakes on the fault centuries ago caused a parts of Seal Beach near the Orange County coast to sink 3ft in just seconds.
In total three quakes over the last 2,000 years on nearby faults made ground just outside Los Angeles city limits sink as much as 3ft.
Today that could result in the area ending up at or below sea level, said Cal State Fullerton professor Matt Kirby, who worked with the paper´s lead author, graduate student Robert Leeper.
The study showed that land within major Californian seismic faults could sink by 1.5 and three feet instantly.
The last known major quake occurred on the San Andreas fault in 1857.
Seismologists estimate the 800 mile-long San Andreas, which runs most of the length of the state, should see a large quake roughly every 150 years.
‘It´s something that would happen relatively instantaneously,’ Kirby said.
‘Probably today if it happened, you would see seawater rushing in.’
The study was limited to a roughly two-square-mile area inside the Seal Beach National Wildlife Refuge, near the Newport-Inglewood and Rose Canyon faults.
Kirby acknowledged that the exact frequency of events on the faults is unclear, as is the risk that another quake will occur in the near future.
The smallest of the historic earthquakes was likely more intense than the strongest on record in the area, the magnitude 6.3 Long Beach earthquake of 1933, which killed 120 people and caused the inflation-adjusted equivalent of nearly a billion dollars in damage.
Today, the survey site is sandwiched by the cities of Huntington Beach and Long Beach, home to over 600,000 people.
Nearby Los Angeles County has a population of 10 million.
Seismologist John Vidale, head of the University of Washington-based Pacific Northwest Seismic Network, said after reviewing the study he was skeptical such powerful quakes could occur very frequently in the area.
Kirby noted that the team could only collect soil core samples within the relatively undisturbed refuge.
He said that taking deeper samples would shed light on the seismic record even further back, potentially giving scientists more examples of similar quakes to work from.
A report from the U.S. Geological Survey has warned the risk of ‘the big one’ hitting California has increased dramatically.
Researchers analysed the latest data from the state’s complex system of active geological faults, as well as new methods for translating these data into earthquake likelihoods.
The estimate for the likelihood that California will experience a magnitude 8 or larger earthquake in the next 30 years has increased from about 4.7% to about 7.0%, they say.