November 25, 2013 in City

The Rock Doc: Cascadia earthquake could bring severe damage to West Coast

E. Kirsten Peters
 

“It’s 8:16 on a chilly, wet morning. … You’ve just arrived at work and are pouring a cup of coffee when you become aware of a low rumbling noise. Within seconds, the rumbling becomes a roar, the floor beneath you heaves, and the building begins to pitch and shake so violently that you’re thrown to the floor. The roaring is joined by a cacophony of crashing as windows shatter and every unsecured object in the room – from the desk chair to the coffeepot – is sent flying. Shaken loose by the shuddering and jolting of the building, dust and ceiling particles drift down like snow. Then the lights flicker and go out.”

That’s the arresting start of a new report produced by several government agencies that describes what can happen when a magnitude-9.0 earthquake hits what’s called the Cascadia Region. That’s an area that stretches from the coast of Northern California north through western Oregon, Washington and southwestern British Columbia.

The quake will be triggered by movement along the faults between the oceanic tectonic plates and the plate on which North America rides. When the plates move suddenly, absolutely enormous amounts of energy are released, with violent shaking of the ground and tsunamis as the result. The report that describes all this is “Cascadia Subduction Zone Earthquakes: A Magnitude 9.0 Earthquake Scenario.”

Cascadia isn’t the only place in danger of having major earthquakes. Most famously, the San Andreas and associated faults in California are a constant threat to local residents. And the New Madrid fault zone, centered where the states of Missouri, Kentucky and Tennessee come together, is a threat to the lower Midwest. Finally, states as different as South Carolina and Alaska also run the risk of significant earthquakes. In short, the U.S. has a number of regions where enormous amounts of energy can be released over the span of just seconds, with resulting damage to buildings, roads, power lines and pipelines.

The scale used by geologists to measure earthquakes is complex. In California, the Loma Prieta quake of 1989 had a magnitude of 6.9. In 2002 a quake with magnitude 7.9 struck Denali Park, Alaska. The Alaskan quake, measuring a single unit higher on the magnitude scale, released more than 30 times more energy than the Loma Prieta quake.

The most recent mega-quake in Cascadia is estimated to have had a magnitude between 8.7 and 9.2. It occurred on Jan. 26, 1700. We know about it both from physical evidence and from written records of a tsunami that arrived in Japan. The sobering fact is that we could have a similar event again, and at any time.

It behooves those of us who live in earthquake country – whether in the lower Midwest, California or Cascadia – to educate ourselves about risks. Having several days worth of food and water on hand, and a way to cook up some vittles, are simple goals most of us can achieve.

Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard universities. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.


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