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Earthquakes

OREGON AT RISK
Earthquakes and other natural hazards


A downloadable PDF version (1.4 MB) of this article from
the Winter, 2001 issue of Cascadia is available; click here.

Oregon at risk
by Lou Clark, Earth Science Information Officer

WHAT CAN YOU DO TO PREPARE IN YOUR COMMUNITY?
Imagine this:
You’re on vacation on the Oregon coast the last week of a sunny August. Without warning, the ground starts to shake, bringing you to your knees. For more than three minutes the earth is moving so violently, you can’t stand up. Bookshelves fall, dishes crash to the floor, windows shatter; the sound is deafening.

Suddenly, it’s over. After gathering your family together, you remember seeing the tsunami evacuation signs on Hwy. 101. You go to your car, but realize driving is not an option, because the road has buckled, and water is pouring onto the road from a broken water-main pipe. Picking up your toddler, you hurry your family up the evacuation route, until you’re at about 100 feet in elevation above the beach. A few minutes later, as you start to relax, you see a 30 foot wall of water cover the beach below, tossing cars, trees and even part of the motel like kindling. You realize all your beach stuff is gone and you wonder about your home, family and friends back in the Willamette Valley.

What you will not know for a while is this was a Cascadia subduction zone earthquake, and the devastation runs from Vancouver, British Columbia to Eureka, California. It could be days before relief arrives, and months before all services are restored.

This map shows only the known faults in Oregon. Faults that have moved most recently are shown in red.
Although this story may read like pulp fiction, scientists agree that a similar occurrence can happen at any time. Scientists also know the last Cascadia earthquake like the one just described was probably a magnitude 9 on January 26, 1700 and that these types of earthquakes have occurred many times in the Pacific Northwest in the last few thousand years.

Whatever size of earthquake your community can reasonably expect, the same preparation steps can be taken to prevent damage and protect lives.

Most earthquakes in Oregon are small in size, but many can produce significant damage at a local level. It’s not just people in western Oregon who are at risk: the last earthquake-related deaths were in Klamath Falls, and there have been several swarms of small earthquakes in eastern Oregon in the last few years.

Is your community prepared? A large earthquake will inevitably produce damage, but your preparations can keep it from being a catastrophe. A 1988 magnitude 6.8 earthquake in Armenia caused 25,000 deaths, but the 1989 magnitude 7.1 Loma Prieta quake that struck the San Francisco Bay area caused only 62 deaths. Whatever size of earthquake your community can reasonably expect, the same preparation steps can be taken.



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