Los Angeleans were given an unexpected alarm call from Mother Nature on Monday morning as an earthquake shook the city at around 6.25am.

The earthquake was initially graded at 4.7 on the Richter scale, but this reading was reduced to 4.4 a short time later.The areas bearing the brunt of the shaking were Santa Monica, Beverly Hills, Pacific Palisades, and West Los Angeles.This is the largest quake to hit Southern California this year, though the north of the state was rocked by an earthquake last week.

On 9th March, a 6.9-magnitude earthquake occurred at a depth of four miles off the coast of Northern California, 50 miles west of Eureka. Though the quake was the largest the area had experienced since a 7.2 shaker in 2010, fortunately no significant damage or injuries were sustained by locals in the area. The recent quakes have prompted officials to question the potential risk of larger earthquakes in California, and the latest predictions are not good.

Researchers now suggest that the fault line responsible for the Eureka earthquake, the Cascadia fault, poses far more of a threat than previously thought. This fault system is normally overshadowed by its larger and more infamous sibling, the 800 mile long San Andreas fault, but now experts believe that the risk from the 700 mile Cascadia subduction zone could be even more dangerous and should not be underestimated.

The fault runs offshore in the Pacific Ocean, from Northern California to Vancouver Island, and scientists are concerned that if it triggered a large quake in the region of 9.0 magnitude, then it has the potential to cause a monumental disaster. Its coastal location could generate a massive tsunami that could obliterate coastal towns and cities and devastate roads, bridges and power lines.

It is forecast that the giant wave could result in the deaths of up to 10,000 people, and the cost of disaster relief and repairs could top $70 billion.

"Katrina was a worst case scenario for hurricanes in the gulf. And a Cascadia would be the worst case scenario for tsunamis on the West Coast," said Paul Whitmore, director of the National Tsunami Warning Center in Alaska.

The fault is known to have caused very large earthquakes in the past: on Jan. 26, 1700, the subduction zone generated an earthquake that was so large, stretches of the Pacific coastline sank by five feet, paving the way for a colossal tsunami which annihilated everything in its path.

Los Angeleans have been preparing for "The Big One" for years with shining the spotlight on the San Andreas fault; now, however, it is believed that the northern Cascadia fault could produce a disaster to eclipse all other scenarios. A SeattlePI.com report revealed that the Northwest is due for a massive earthquake, and experts in Washington issued a gentle reminder in January that it was the 314th anniversary of the last megathrust quake in the Cascadia Subduction Zone.

Dr. Audrey Dallimore, Associate Professor at Royal Roads University and author of a recent study examining the risk from Pacific earthquakes, stated: "We have identified 22 earthquake shaking events over the last 11,000 years, giving an estimate of a recurrence interval for large and megathrust earthquakes of about 500 years. However, it appears that the time between major shaking events can stretch up to about a 1,000 years.

"The last megathrust earthquake originating from the Cascadia subduction zone occurred in 1700 AD. Therefore, we are now in the risk zone of another earthquake. Even though it could be tomorrow or perhaps even centuries before it occurs, paleoseismic studies such as this one can help us understand the nature and frequency of rupture along the Cascadia Subduction Zone, and help Canadian coastal communities to improve their hazard assessments and emergency preparedness plans."

An earthquake generated from the Cascadia fault could affect a wide area to the north and south including some major cities such as Seattle, Washington; Vancouver and Victoria, British Columbia;Portand, Oregon; and Sacramento, California.

So, what can those in high-risk areas do in the event of such a catastrophe?

Natural disasters such as the 2011 Japan tsunami and Hurricane Katrina have inspired authorities to begin preparing for a major quake on the Cascadia fault, and the recent quakes in California should serve to give officials in high risk areas another nudge to take the risk very seriously.

It is thought that residents would have approximately fifteen minutes to get to the safety of higher ground, and in areas without any natural elevation such as Grays Harbor County, Washington, vertical evacuation centers are being built in one school on top of a gymnasium, so that that teachers and students can quickly evacuate to higher ground in the event of a tsunami. The construction of another 50 "tsunami safe havens," such as artificial hills that could hold as many as 800 people, is being discussed by officials in Washington.

National Oceanic and Atmospheric Administration tsunami researchers are also testing new tsunami detectors off the Oregon coast, in the hope that these will provide earlier warnings about the size of incoming waves. The new sensors located deep on the ocean floor should provide information on a tsunami’s size in as little as five minutes, a process that currently takes about half an hour.

The disaster cannot be avoided, and all we can do is to make advance preparations to minimise damage and loss of life. Could the authorities be doing more and, if so, what?

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