THE SERIES of large earthquakes that brought death and destruction to Mexico last month may have triggered a chain reaction of tremors on the global scale.
Geologists are out with a startling warning that Southern California is overdue for a major and possibly catastrophic earthquake. A new study says it's expected to hit along the San Andreas Fault north of Los Angeles. It could have a magnitude of 7.5 or higher.
Mexico was rattled last month when the biggest earthquake in more than a century, measuring 8.1 on the Richer Scale, struck off its southern coast, killing 90.
Then, just over a week later, Mexico City was virtually flattened by a magnitude 7.2 earthquake that reduced entire communities to rubble and killed 300.
In the following days a swarm of tremors greater than magnitude 5.0 continued to blight the nation.
These tremors were thought to be “aftershocks”, when stress is transferred from one fault line to another close by.
Natural disaster specialist Dr Simon Day told Daily Star Online similar aftershocks may have caused the record magnitude 8.1 quake through a process known as “stress triggering”.
He said: “For several months leading to the big 8.1 earthquake, there was a sequence of smaller earthquakes on a zone further south.
“This may have stressed the deep fault zone that produced the 8.1 earthquake.
“That then stressed the fault zone in the part of the slab further north that produced the 7.1 earthquake a week later."
Dr Day, of University College London, said research shows this process could continue in the coming weeks and months, causing small and large earthquakes on neighbouring fault lines.
POWERFUL: A map shows the epicentre of the magnitude 8.1 earthquake in Mexico
EARTHQUAKE FEARS: California is long overdue a major tremor, experts believe
The chain reaction could have global consequences, with many countries in the Pacific Ocean at risk from a large destructive earthquake.
He said: “There is a huge and long-standing argument in seismology, also involving statisticians, about whether the significance of such sequences extend globally producing temporal clusters of earthquakes on a global scale.
“Seismological standard theory says that earthquake occurrence is random.
“But when you get sequences in adjacent fault zones, stress transfer effects are physically plausible especially where continuous plate boundaries of the same type are involved.”
Mexico is situated in a notorious earthquake "danger zone" known as the Ring of Fire, where up to 80% of the world's tremors occur, US Geological Survey said.
David Shelly, research seismologist with the USGS, told Daily Star Online that the Ring of Fire is prone to earthquakes “because much of it follows boundaries between tectonic plates”.
California, which also sits on the Ring of Fire, is on earthquake alert too after experts warned a "big one" tremor is inevitable.
Even SWAT Teams are Helpless Against This...
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.
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.
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A view of the San Andreas fault in the Carrizo Plain. Scientists from California State University Fullerton and the United States Geological Survey found evidence the older quakes have caused the land to fall by three feet
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 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
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.
The official USGS forecast for California earthquakes now predicts a 16 percent chance of an M7.5 quake or larger on this section of the fault within the next 30 years. Shown here is the chance of an earthquake across California over the next 30 years
CALIFORNIA AT RISK OF DEVASTATING MEGAQUAKE
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.
'We are fortunate that seismic activity in California has been relatively low over the past century,' said Tom Jordan, Director of the Southern California Earthquake Center and a co-author of the study.
'But we know that tectonic forces are continually tightening the springs of the San Andreas fault system, making big quakes inevitable.'
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.
PLANS FOR 'THE BIG ONE'
Federal, state and military officials have been working together to draft plans to be followed when the 'Big One' happens.
These contingency plans reflect deep anxiety about the potential gravity of the looming disaster: upward of 14,000 people dead in the worst-case scenarios, 30,000 injured, thousands left homeless and the region's economy setback for years, if not decades.
As a response, what planners envision is a deployment of civilian and military personnel and equipment that would eclipse the response to any natural disaster that has occurred so far in the US.
This haunting photograph shows people walking through rubble in San Francisco on 18 April 1906. Many people are worried that the city and LA, for example, would look like this again due to a massive quake
There would be waves of cargo planes, helicopters and ships, as well as tens of thousands of soldiers, emergency officials, mortuary teams, police officers, firefighters, engineers, medical personnel and other specialists.
'The response will be orders of magnitude larger than Hurricane Katrina or Super Storm Sandy,' said Lt. Col. Clayton Braun of the Washington State Army National Guard.