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March 30th, 2011 MARTY SMITH | Dr. Know
 

Dr. Know: Big Quake - Sez Who?

drknowILLUSTRATION: Hawk Krall
     
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A colleague gave me this “WWsomething” rag, and I had the misfortune of opening it to your column. So, there was a big coastal earthquake 300 years ago, huh? How do they know?  Who was in Oregon in roughly 1711 to know there was “a big one”? —Bill T.

Jeez, Mr. Rude—you kiss your mother with that tongue? Lucky for you, the answer to your question involves such a triumph of science that I’ll overlook your desperate need to get laid and answer it.

Geologists believe our friendly neighborhood bringer of apocalypses, the Cascadia subduction zone, has produced seven magnitude-8-plus quakes in the past 3,500 years, with a periodicity ranging from about 210 to 910 years. They can tell this by the geological record, though of course the actual dates are approximate.

However, the particular quake you so brazenly doubt can be dated with a bit more accuracy: It happened on Jan. 26, 1700, at around 9 pm. The date was determined in a landmark 2005 paper, “The Orphan Tsunami of 1700,” by University of Washington paleoseismologist Brian Atwater, et al. 

As a tsunami authority, I imagine Atwater has been, um, deluged with media requests lately, which may be why he didn’t return my emails. (Then again, maybe he just doesn’t like penis pictures—who can say?) Either way, his research shows how a well-documented tsunami in Japan—one whose parent quake was previously unknown—had to have been caused by a Cascadia subduction quake, right here in what would eventually become our back yard. Boom! Science: 1; mean letter writer: 0.

And to those who think I give too much play to the coming quake: Say what you want, but I’m pretty confident that when our Sendai-level event actually happens, everybody will agree it’s worth some ink. Till then, I’m just trying to beat the rush.

 
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