Preparing the Pacific Northwest for an Unprecedented Tsunami

EarthzineCoastal Environments 2016, Original, Themed Articles

In preparing the Pacific Northwest for The Really Big One, modelling and drills can be key to understanding a danger the region has yet to fully witness.

The Direction Wave Basin at O.H. Hinsdale Wave Research Laboratory. Image Credit: Oregon State University and National Science Foundation.

The Direction Wave Basin at O.H. Hinsdale Wave Research Laboratory. Image Credit: Oregon State University and National Science Foundation.

The Large Wave Flume resembles a large, concrete canal, a little shorter than a football field. At its deepest, it’s 15 feet, and an orange box sits suspended partially in the water about midway down the flume.

On the surface of the water, an isolated wave hastens toward the box. From an overhead vantage point, it looks like an insignificant blip. Even when the wave breaks, it still remains unassuming—at least at this 1:10 scale.

Here at the O.H. Hinsdale Wave Research Laboratory at Oregon State University in Corvallis, Oregon, the Large Wave Flume can be used to model tsunami waves and storm surges. Lab Director Pedro Lomonaco says the largest wave the flume can generate is comparable to ‰ÛÏa 25-ton truck running into your house at 25 mph.‰Û

Such forces are on par for a predicted Cascadia subduction zone-generated tsunami.

In the Cascadia subduction zone, the Juan de Fuca plate is forced under the North American plate in a process called subduction. This slow-going plate gets stuck, buckling the plate above it. This set-up can lead to sudden slipping of the plate, causing powerful earthquakes. Past earthquakes generated by subduction zones include the 1960 Chilean quake—the largest magnitude quake ever recorded—and the 2004 Indian Ocean quake—one of the deadliest natural disasters in recent history.

A schematic of the Cascadia subduction zone (CSZ), including recorded earthquakes. Image Credit: USGS

A schematic of the Cascadia subduction zone (CSZ), including recorded earthquakes. Image Credit: USGS

This potential high magnitude earthquake has been called many things from, ‰ÛÏFull Rip 9.0‰Û to ‰ÛÏThe Really Big One.‰Û The predicted quake could be enough to disrupt life from British Columbia to Northern California, home to more than 11 million people. Along the coast, however, another danger can follow on the heels of a large quake. As the plates slip, they displace water, creating a large wave called a tsunami. Displaced water can pummel through low-lying areas within 30 minutes of a larger quake.

Earthquakes and tsunamis are unique beasts, for in the absence of frequent, predictable, and easily observable occurrences, modelling becomes key. While some models are computer-based, others, like at the Hinsdale lab, are about as large and physical as one can get. Lomonaco says the physical modelling undertaken at the lab is necessary for the type of threat faced with a tsunami. Much like earthquakes, we don’t know when they will occur or necessarily where, so replicating tsunami-like waves in a controlled research environment is essential.

The orange box in the Large Wave Flume represents a generic building, elevated on stilts above the ground. Readings from sensors on the box communicate the forces and stresses the building experiences under different sizes and types of waves.

Engineering structures to withstand intensive shaking and coastal tsunamis is one of many challenges that researchers face.

Dan Cox, Lomonaco’s colleague at Oregon State, looks at the civil engineering side. Cox’s research involves the Cascadia Lifelines Program, or CLiP, which identifies five major lifelines that a natural disaster could disrupt: transportation, water, power systems, communication, and buildings. Cox focuses on ‰ÛÏthe interdependencies among all these different systems.‰Û

‰ÛÏIf the electricity goes down,‰Û he explains, ‰ÛÏnow I can’t run the pumps for the water or the pumps for the fuel to get the trucks back on the road to fix the electricity so people have water.‰Û

An aerial view of Sendai, Japan after the 2011 quake. Image Credit: U.S. Navy

An aerial view of Sendai, Japan after the 2011 quake. Image Credit: U.S. Navy

Cox pulls up a model on his computer, where little human dots flee Newport Beach State Park for designated evacuation meeting points. The current evacuation route for the park directs people to the park entrance. In a modelled Cascadia tsunami, he shows that by following this route few would make it out of reach of the oncoming water. Half of the human dots in the model go by foot, and some of these walkers make it to the safe meeting point, while others don’t. The other half get into their cars, but gridlock halts all but a few, those left behind remain stuck in their cars as they are inundated by blue. There’s a more efficient path to safety, but the park would need an easement for the route required.

Cox says he’s beginning to understand that ‰ÛÏ(people) need multiple signs to do something.‰Û

‰ÛÏSometimes it’s a natural sign like smoke, or an artificial sign, like the ringing of the fire alarm,‰Û he explains, ‰ÛÏand sometimes it’s the third sign ‰Û_ you see your colleague leaving the building, and you say ‰Û÷Okay, I’m going to go too.’‰Û

A tsunami evacuation route sign in Seaside, Oregon. Image Credit: M.O. Stevens

A tsunami evacuation route sign in Seaside, Oregon. Image Credit: M.O. Stevens

Problems like this require an understanding of the geoscience, infrastructure, and influences on people’s decision-making skills, to name a few.

Understanding the failings in our current systems is half the battle. The other is action.

Over four days this year, multiple private and government agencies in the Pacific Northwest tested themselves with an emergency drill called Cascadia Rising. They aimed to test 14 core capabilities, many overlapping with CLiP’s lifelines. And with good reason: in the Exercise Scenario Document, the design team noted that ‰ÛÏlife-saving and life-sustaining response operations will hinge on the effective coordination and integration of governments at all levels ‰ÛÒ cities, counties, state agencies, federal departments, the military, and tribal nations ‰ÛÒ as well as non-governmental organizations and the private sector.‰Û

Oregon State University also has decided to build a new research center at the existing Hatfield Marine Science Center in Newport, Oregon. The planned location is in the tsunami inundation zone, but the goal is to build a structure that can withstand predicted earthquakes and tsunamis. According to OSU President Edward J. Ray, ‰ÛÏthe building might also serve as a safe destination for others who work at or visit nearby businesses or attractions, but who could not physically reach Safe Haven Hill.‰Û

Although in the United States this threat is unique to one small corner, the area is not the only one facing these dangers. Subduction zones similar to Cascadia exist off the coast of Japan and Chile.

We can learn lessons from these other places. The tsunami generated by 2011 Japan earthquake was vastly underestimated. Even though warning systems were in place, more than 15,000 lives were lost, according to Japan’s National Police Agency.

In addition to needing coordination and planning, our understanding of this threat is often changing. An article published in Marine Geology in August by researchers from Oregon State University, Camosun College in British Columbia, and Instituto Andaluz de Ciencias de la Tierra in Spain indicates that the section of the Cascadia subduction zone off the coast of Oregon ruptures more frequently than previously thought. Through coring sediments, researchers also concluded that rupturing of the entire zone at once is more likely.

In short, larger earthquakes have been and will continue to be more frequent.

The issue still remains that recent human inhabitants haven’t witnessed such a large scale Pacific Northwest event. We won’t know exactly what an earthquake generated tsunami looks like until it happens. In order to prepare, modelling can provide tools to help envision that event and the aftermath.

Cox is hopeful. ‰ÛÏI think what’s interesting about the Cascadia problem is that it’s new,‰Û he says, ‰ÛωÛ_ we’re facing these challenges for the first time in many places, so you could say it’s ripe for saying, ‰Û÷Hey, let’s try to solve this problem.’‰Û

See also:åÊEarthquake Country.

Abby Burlingame is a Pacific Northwest native, who recently graduated from Bryn Mawr College in Philadelphia with an undergraduate degree in geology.