The Shakin’est Place in Oregon

From the Spring 2007 Oregon Paleo Planet,

Think about earthquakes in Oregon, and the Willamette Valley, or maybe the coast come to mind as most under threat.
But so far, in 2007, north central Oregon’s Maupin Seismic Zone, just over the hill has been by far the most shakin’ place
in the state.

As if to ring in the New Year, on New Years Eve, a magnitude 3.1 quake shook the ground about 10 miles northwest of
Shaniko. Since then, two or three quakes each week have rattled the earth around Johnson Ridge, Deep Creek, and Cottonwood
Creek, all eight to 12 miles NW of Shaniko, and a bit north of Bakeoven Grade.


The shaking has been mild—that’s the typical pattern for the Maupin Seismic zone so far. These quakes are shallow, geologically
8 to 12 miles deep. But in 1976, a 4.8 magnitude temblor shook the ground along this zone. This quake was felt
over an area of more than 30,000 square miles. Foreshocks preceeded it for about 10 days, according to OSU geophysicist
Richard Couch. This is an area to be wary of.

Exactly what drives the Maupin quakes is still a mystery. Measurements of the 1976 quake indicated that motion was compressional,
along a deep thrust fault. However, there is no known expression of this deep fault in local surface geology.

We DO know that these quakes are caused by compression from south to north as plate tectonics shoves the Cascades
and Coast range north into Washington’s underbelly. Like it or not, plate tectonics is trying hard to transport us all to Seattle.

Let’s hope that it remains a smooth ride.

In case you missed it there was another 1.4 in the Maupin area today.

Maupin Earthquake Mover Mike

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