New research from Oregon State University takes steps toward understanding how tsunamis destabilize soil, which is key to building and retrofitting infrastructure that can withstand a disaster.

“Traditionally, in the past, the structural engineers have only thought about what happens at the soil level and above, and the soil engineers have thought about what happens at the surface and below,” said Ben Mason, an associate professor at Oregon State’s College of Engineering.

Seaside bridges

Several bridges in Seaside have been determined to be insufficient in an earthquake or tsunami.

The project combines what scientists know about how the soil will affect the structure, and how the structure will affect the soil. The findings could help communities on the North Coast prepare for a Cascadia Subduction Zone earthquake and tsunami.

“Ultimately you have to understand the marriage between the two during both the earthquake and the tsunami to be able to develop reasonable designs,” Mason said. “It’s a symphony — it really is.”

The research was conducted in collaboration with the University of California, Davis and published in July.

Up until now, scientists have been speculating about how water pressure changes the soil, but now they have experimental data they can use to improve their computer models and run simulations to see how infrastructure in different coastal towns will be affected based on their soil density and existing structures.

Building sustainable infrastructure depends on the soil of a given location. How engineers build a bridge should depend on the soil, and how soil moves depends on how engineers build the bridge, Mason said.

“The perfect example of that is the 1986 Mexico City earthquake,” Mason said. “The city is built on an ancient lake bed and there’s buildings that got absolutely demolished there due to a relatively modest earthquake.

“And then if you go just barely up the mountain to where it’s rock, none of the buildings saw any damage. So, the soil is extremely important to how the bridges and buildings and infrastructure is going to fare during an earthquake and a tsunami.”

Mason plans to continue having conversations with local governments on the North Coast to help educate people on what they should expect to see happen in a large earthquake and tsunami.

“In terms of actual communities and engineers or city managers, they’re largely going to be concerned with just evacuation procedures during the hazard to try to get their population to higher ground or to safety and then setting up emergency shelters and relief after the event,” he said.

The Oregon Department of Transportation is going to be responsible for moving the needle on retrofitting critical bridges, as it is very costly, he said. And since it is difficult for coastal towns to obtain enough funding to improve infrastructure, they need to prioritize their strategies.

“When you start talking about a hazard that might only occur, let’s just call it every 500 years, it’s very hard to convince governments to spend money to invest in resources and especially retrofit bridges or infrastructure,” Mason said.

“The No. 1 thing I’m always a proponent of is, which I think is a lot cheaper and a lot more effective, is educating the population and the government officials about what we expect to happen during the next natural disaster and what are some more cost-effective strategies for keeping the population safe.”

As local governments develop emergency preparedness plans and scientists continue to improve research methods, Mason said everyone can do a better job of communicating.

“Sometimes when the scientists come and talk to government officials, they don’t really know how to interact with people very well and they can come across as like the annoying computer guy who knows more than you and can’t really talk without using jargon,” Mason said.

“A lot of times, that’s not even ill-intentioned, it’s just that we’re not taught the skills of how to do that. And I think perhaps because of that maybe there’s a boundary between scientists and city managers ... and maybe that brings some reluctance to reach out and talk to the scientists. It’s a vicious cycle, really.”

Nicole Bales is a reporter for The Astorian, covering police, courts and county government. Contact her at 971-704-1724 or nbales@dailyastorian.com.

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