'Big One' will come, but when?

In the words of Roseanne Roseannadanna, what's this I hear about an earthquake that's about to hit Southern Oregon? My friends tell me the Mail Tribune had a story recently saying the Big One is coming.

— Not Roseanne Roseannadanna, Medford

Well, Not Roseanne Roseannadanna (nice "Saturday Night Live" reference, by the way), you heard partly right: Officials are predicting a big earthquake will hit Southern Oregon, but they don't know when.

We had a few other comments from people who had fled to their underground bunkers to escape imminent destruction after they read a story titled "Bracing for the Big One" in the Sept. 12 Muddy Tributary. It seems they were put on edge by the lead paragraph, which read:

"State emergency officials will spend next week urging Southern Oregon residents to prepare for a magnitude 9.0 earthquake that could seriously disrupt food, water, transportation and other vital services."

As you can see, there is no date attached to when that 9.0 quake is expected to hit. That apparently led some people to expect the worst, but you can tell your friends that they can come out from under their dining room tables, No Roseanne Roseannadanna.

The truth is, officials don't know when the Big One is going to hit, but they are pretty darn sure it is going to happen at some point. Could be tomorrow, could be 75 years from now, but all signs point to the likelihood it will occur.

That's because the Cascadia Subduction Zone lies off the coast of Oregon. The subduction zone runs from Cape Mendocino, Calif., to British Columbia. It's where the earth's plate underneath the Pacific Ocean pushes under the North America plate. It last gave way on Jan. 26, 1700, generating a magnitude 9 earthquake and a tsunami that washed away houses in Japan.

The geologic record reveals 41 of these huge earthquakes over the past 10,000 years and officials say we're probably due for another one. They just don't know when exactly. (If they did, there would probably be quite the traffic jam as we all headed to Idaho for vacation just before the predicted date.)

The story you referred to provided information about an upcoming talk by Althea Rizzo, Geologic Hazards Program coordinator for the Oregon Office of Emergency Management. She will be in Medford on Friday, Sept. 20, to discuss earthquakes and preparedness. The talk will be from 3 to 5 p.m. in the council chambers in Medford City Hall, 411 W. Eighth St., Medford. She also plans to speak in other Southern Oregon cities.

And you'll be happy to know they recently retrofitted City Hall to make it more earthquake-resistant.

Send questions to "Since You Asked," Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by email to youasked@mailtribune.com. We're sorry, but the volume of questions received prevents us from answering all of them.

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