California’s Major Quake and Tsunami Threat: Cascadia Subduction Zone

Computer simulation of a tsunami generated by a large earthquake on the Cascadia subduction zone in 1700, created by Kenji Satake of Japan's National Institute of Advanced Industrial Science and Technology. This view shows the tsunami 10 hours after the earthquake triggered it.

Computer simulation of a tsunami generated by a large earthquake on the Cascadia subduction zone in 1700, created by Kenji Satake of Japan’s National Institute of Advanced Industrial Science and Technology. This view shows the tsunami 10 hours after the earthquake triggered it.

Coastal California towns washed away. Up to 10,000 deaths. $70 billion in damage left behind. And the infamous San Andreas fault didn’t move an inch.

Against traditional thinking, it’s not the San Andreas fault that could do the most damage to California. It’s actually the Cascadia subduction zone. Now, scientists are trying to deliver a serious message to citizens: although the San Andreas fault is capable of producing The Big One, the Cascadia subduction zone, located off the coast of the Pacific Northwest, could produce The Really Big One.

A 7.6-magnitude earthquake in Turkey killed more than 17,000 people in the summer of 1999. (U.S. Navy/Getty Images)

A 7.6-magnitude earthquake in Turkey killed more than 17,000 people in the summer of 1999. (U.S. Navy/Getty Images)

That’s the message the Cascadia Region Earthquake Workgroup has been trying to pass along to states along the West Coast. According to a SeattlePI.com report, the Northwest is due for a massive earthquake.

If the “megathrust” quake happens along the Cascadia subduction zone, Seattle could be destroyed and many areas to the south could be inundated by a large tsunami. Only 22 such earthquakes have occurred in the last 11,000 years, according to Dr. Audrey Dallimore, associate professor at Royal Roads University in British Columbia.

History shows us that the subduction zone, is capable of producing massive earthquakes as high in magnitude as 9.0, according to a Los Angeles Times report. On the evening of Jan. 26, 1700, an earthquake occurred along the subduction zone that was so large, stretches of the Pacific coastline dropped by as much as five feet, allowing a huge tsunami to devastate everything along the shore, scientists found.

The first of two of the top-10 deadliest earthquakes of the last 25 years that occurred in India was a 6.2 temblor that killed 9,748, according to the USGS.

The first of two of the top-10 deadliest earthquakes of the last 25 years that occurred in India was a 6.2 temblor that killed 9,748, according to the USGS.

If an earthquake that powerful were to occur again off the now-populated coast, the results would be catastrophic. A huge tsunami would move away from the subduction zone in all directions, crashing onto the California coast. It would wipe out highways along the shore and, even worse, towns full of people.

Areas are preparing for the possibility of The Big One before it happens. Because residents would have about 15 minutes to get to safety, the L.A. Times reports, evacuating to higher elevations may be the only option. In Grays Harbor County, Wash., they’re beginning to build vertical evacuation centers atop sturdy gymnasiums that will allow teachers and students to quickly evacuate to higher ground in case a massive earthquake pushes a tsunami toward the coast.

This 'ghost forest' near the mouth of the Copalis River, Washington, was killed by saltwater tides after an earthquake in 1700 caused the land to subside.

This ‘ghost forest’ near the mouth of the Copalis River, Washington, was killed by saltwater tides after an earthquake in 1700 caused the land to subside.

Subduction zones are especially prone to large tsunamis because as one plate is pushed beneath another, the plates continue to push and lock against each other until stress builds up so much that they slip, according to the Washington State Department of Ecology. Scientists are worried this is currently happening at the Cascadia subduction zone, and any time energy is built up by shifting plates, a large earthquake could occur.

The California Geological Survey says the Cascadia subduction zone had produced six earthquakes of magnitude 7.0 or greater in the last 100 years – and a 6.8-magnitude tremor occurred Sunday night off the coast of Ferndale, Calif. – but it’s the 9.0 of 314 years ago that has scientists warning California residents to focus their attention on a sea up north.

Crash

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