Maupin Keeps on Shaking With Micro-Quakes

Five more “micro-earthquakes” have been recorded in the past two weeks near the small north-central Oregon town of Maupin, continuing a more than 4-year mysterious “swarm” of deep, relatively small quakes.

The largest occurred around 2:06 p.m. Tuesday, measuring 2.6 magnitude and centered eight miles east-southeast of Maupin, at a depth of about 14 1/2 miles below the surface.

Another of similar strength, 2.5, was recorded on March 27, after one of 1.6 on March 23 and others of 1.5 and 1.0 on March 30, all in the sames spot.

Wasco County sheriff’s deputies said Tuesday they didn’t know another of the tiny shakes had occurred.

Back in late December, a 3.6-magnitude quake was recorded, at a depth of just over 10 miles, according to the Pacific Northwest Seismograph Network, based at the University of Washington.

Very few people in the relatively unpopulated area have felt any but the largest of these quakes, which began shaking the area back in November of 2006. Another 3.6-magnitude quake shook the area back in early January of 2010.

The swam that hit a peak of 200 quakes in 2007 had slowed to 150 the following year and just 20 to this point in 2010, so word of another decent-sized shaker was a bit of a surprise to Jochen Braunmiller, an Oregon State University research assistant who has studied the Maupin quake swarm.

“It has been slowing down quite a bit, so quite frankly, I was surprised by another magnitude 3.6,” Braunmiller told KTVZ.COM last December. “Last January, I thought that maybe it was the last big one. At some point, I was sure it was stopping, but now we see, not this year — maybe next year.”

Coincidentally, the last quake of similar size was on Jan. 2 of last year, so this unexplained quake swarm seemed to be marking the new year yet again.

The biggest of the swarm, in July 2008, was a 4.2-magnitude temblor, the biggest quake in the region in 32 years.

Seismologists monitoring the shaking still have more theories than definitive answers as to why the area has been hit by so many small quakes, since there are no volcanoes or known major faults in the area.

Some researchers have theorized that liquids 10 miles below the surface are the culprit. The depth of the quakes also is unusual, pointing to possibly some material like carbon dioxide or a salty brine are caught in a pocket deep below the surface, Wes Thalen, seismologist with the Pacific NW Seismograph Network, told The Bulletin in late January.

Braunmiller had a different suggestion, saying the water could be acting as a lubricant, making it easier for rocks under stress to snap and cause the little quakes.

The current swarm near Maupin slowed after the initial year, when more than 150 small quakes were recorded, seven above magnitude 3. But clearly, it’s not over yet.

Several such swarms have been detected in the state over the years, but researchers often don?t have the budget to study them, according to Ian Madin, chief scientist for the Oregon Department of Geology and Mineral Industries. Others have included swarms around Bend, South Sister, Prineville and Lakeview that usually arise, then end.

But the one near Maupin just keeps on rockin? into another year.