Why Washington is particularly vulnerable to earthquakes and tsunamis


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A catastrophic earthquake and tsunami are inevitable for the Pacific Northwest coast, scientists say. Planning for this involves imagining a catastrophe unlike anything seen in today’s United States.

“Thirty or 40 years ago, we didn’t even know that big earthquakes were possible in the Pacific Northwest,” he said. Diego Melgar, seismologist at the University of Oregon.

Scientists now know that the 700-mile fault called the Cascadia subduction zone, 100 miles off the coast of Northern California and extending north to Vancouver Island, could trigger an earthquake of magnitude 9.0 followed by a tsunami, which is exactly what happened in Japan in 2011.

New in-depth images of the fault were recently reported in “Scientific Progress”. Scientists say this confirmed that the subduction zone is broken into 3 to 5 segments, each with its own geology. When the segment of the fault off the coast of Washington ruptures, it risks triggering a devastating earthquake.

Nobody is ready for this.

According to Corina Allen, nothing built before 2005 was designed to withstand the long, powerful Cascadia earthquake.the chief risk geologist at Washington Geological Survey. And tsunami building codes didn’t come into effect until 2016.

“We have bridges, buildings, hospitals, schools, all this infrastructure that is located in places where a tsunami could occur,” Allen said. Will these facilities be able to survive the earthquake and tsunami that would follow? “The answer is no.”

“What keeps me up at night is that I know we are not taking the necessary steps, as quickly as we should, to protect our people,” he said. Yumei Wang, senior infrastructure and risk advisor at Portland State University.

Brick and masonry buildings are most vulnerable to earthquakes. And Wang says wood-frame buildings are particularly vulnerable to tsunami forces. “You can just imagine water invading a typical house,” she adds.

Geological records from the region indicate that, on average, these megaquakes and tsunamis occur every 500 years. There’s no way to predict when this will happen next, but it’s expected to happen again within the next 200 years – or less.

It will be a long process and will cost billions of dollars to modernize existing communities, Allen said. Melgar thinks the effort is worth it. “My children might not see dividends, my grandchildren might not see dividends. “We play a very long game if we do it well.

For those who live and vacation along the Pacific Northwest coast, surviving a tsunami that occurs 15 to 30 minutes after an earthquake depends on how quickly they can reach higher ground. But there may be no safe place to go.

“In Washington, most people who live in the tsunami flood zone don’t have high ground nearby,” Allen said.

In this case, vertical evacuation structures built in the tsunami zone are vital. These structures helped save thousands of lives during the 2011 tsunami in Japan.

People evacuate to the roof of an elementary school after a tsunami warning was announced March 13, 2011 in Higashimatsushima, Miyagi, Japan.

Only three have been built in the Pacific Northwest with four more planned. But Allen estimates that 50 would be needed in Washington alone. Each of the three existing structures could accommodate 400 to 1,000 people, reach up to 76 feet in height and vary in cost. The most expensive, at $62 million, is the Oregon Marine Science Center, Wang said.

The Gladys Valley Marine Science Center at Oregon State University in Newport, Oregon, is designed to survive a magnitude 9.0+ earthquake and resulting tsunami.

“The foundations are deeper than the building is tall, like an iceberg. And the structure itself looks a bit like a car bumper, so large, very heavy debris can hit it.

“We know enough about building codes. We know enough about early warning. We know enough about tsunami evacuation zones that it’s not that bad,” says Melgar.

What’s less clear is whether people are willing to invest billions of dollars to prepare for something that may not happen for 200 years. “It’s an expensive problem to solve,” Allen says. “Maybe we have more time and are able to put the systems in place we need to survive this event.”

The problem is that no one knows how much time is left.

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