Swarm of small quakes occuring at Alaska volcano

Posted: Tuesday, April 06, 2010

ANCHORAGE - A swarm of small earthquakes began Monday at a volcano near Anchorage in what scientists said was a warning that Mount Redoubt could be waking from its slumber.

The Associated Press File
The Associated Press File

"It is reminding us that it is an active volcano," said Rick Wessels, a geophysicist with the U.S. Geological Survey in Anchorage.

The swarm of small quakes started early in the day near the summit of Mount Redoubt, about 100 miles southwest of Anchorage, with a regular pattern often seen when magma is moving inside a volcano, Wessels said.

Researchers plan to fly through the steam plume of the volcano later this week and take measurements of three chemical compounds linked to volcanic activity - sulfur dioxide, carbon dioxide and hydrogen sulfide.

Scientists do not know if the earthquakes will lead to the volcano again becoming explosive, but they said that was a heightened possibility.

Last year, the volcano rumbled and grumbled for months before exploding on Jan. 26, at times producing huge ash plumes and sending mud flows down its flanks. It finally quieted in late September, but there was a similar episode of increased seismic activity in December.

Then came Monday.

"We were going along quietly and all of a sudden, boom, we started getting these small earthquakes," said Steve McNutt, a University of Alaska Fairbanks research professor.

Mount Redoubt is monitored by seven seismometers.

Last year, Mount Redoubt awoke after a magnitude-5.7 earthquake at the mouth of Cook Inlet.

The volcano followed that period of unrest with 19 significant eruptions over several weeks in March and April in which it sent ash plumes as high as 65,000 feet and cloaked parts of south-central Alaska in up to a half-inch of ash.

Residents donned face masks and covered their cars and trucks to keep the ash off the finish and out of the engines.

Mount Redoubt also erupted in 1989 and 1990.

Wessels said the current earthquakes were not connected to Sunday's magnitude-7.2 quake in Mexico just south of the U.S. border.

"We wouldn't expect there to be any connection given the distances," he said.

Alaska is the most seismically active state in the country. In 1964, it experienced a magnitude-9.2 earthquake near Anchorage, the strongest earthquake ever recorded in North America.



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