Earthquakes near Port Heiden rattle all weekend

Apr 1, 2016

No damage reported, and no tsunami warnings issued, after series of quakes near Port Heiden over the weekend.

A cluster of earthquakes shook near the Aniakchak Crater over the weekend, beginning with a 6.2 magnitude quake Friday night at 9:50 p.m.
Credit Alaska Earthquake Center

KDLG:  A series of earthquakes that shook residents of Southwest Alaska over the weekend appears to have no connection to eruptions at Mount Pavlof volcano a week prior.

According to the UAF Alaska Earthquake Center, a 6.2 magnitude quake was reported at a depth of 17.9 kilometers, 15 miles NE of Aniakchak at 9:00 p.m. sharp. Just four seconds later, a 6.4 magnitude quake in the same approximate location but at a depth of 93 kilometers was registered. At 10:00 p.m., a 4.6 magnitude quake shook at a shallower depth, followed by a 3.9 quake 20 minutes later.

"We just got one real good jolt at the lake, then felt a tiny one after that," said Don Lind in nearby Chignik Lake. "Everything's fine down here so far. It had a real slow jerk to it."

John Christensen in Port Heiden said he wasn't aware of any damage, speaking shortly after the biggest of the initial quakes. Residents in Kokhanok, Togiak, Dillingham, and Naknek all quickly reported the quake on Facebook.

Are the quakes tied to activity at Mt. Pavlof, which erupted last Sunday? State seismologist Michael West addressed that in an article days ago.

"Many people have asked why there were no earthquakes in the days prior, or for that matter why the maps continue to show no earthquakes at Pavlof even though it is erupting. After all, aren’t precursory earthquakes one of the primary tools we use in forecasting eruptions? Pavlof is the odd, sneaky exception," West wrote. 

"Pavlof is considered an “open system”. Its frequent eruptions and its style of magma are able to sometimes maintain a relatively open conduit system between eruptions. If the conduit doesn’t solidly freeze up after an eruption, then there is no need to clear out a new one. The mechanics of this are somewhat speculative but the data are pretty strong. Pavlof already erupted in late 2014. When it started up again the other day there was little in the way of precursory seismic indicators. It is easy to imagine this system reactivating with very little energy. As one of our staff, Helena B., put it, "Its cork had already popped". Or perhaps its throat was already cleared," West wrote.

West says the 6.2 magnitude quake was larger than most events recorded in the area in recent decades.

"It's been followed now by a very vigorous aftershock sequence. To date there have been at least two dozen magnitude-3 aftershocks or larger," he said. "These are the little earthquakes that happen around the big one. You know, once the earth has shifted, there are a whole lot of areas around it that need to adjust and get used to the earth's new position. And that's what the aftershocks represent."

The quake and its aftershocks were felt as far away as Dillingham, Naknek and Kohkanok. 

The National Tsunami Warning Center said the Friday quakes were not expected to generate any tsunami danger.