Arrow-right Camera
The Spokesman-Review Newspaper

The Spokesman-Review Newspaper The Spokesman-Review

Spokane, Washington  Est. May 19, 1883
Cloudy 59° Cloudy
News >  Pacific NW

Scientists say recent quake swarm at Mount Rainier is not unusual

UPDATED: Wed., Sept. 20, 2017

A hiker walks the trails near Sunrise in Mount Rainier National Park. (John  Nelson / The Spokesman-Review)
A hiker walks the trails near Sunrise in Mount Rainier National Park. (John Nelson / The Spokesman-Review)
By Sandi Doughton Seattle Times

SEATTLE – Nearly two dozen small earthquakes have rattled Mount Rainier over the past week, but seismologists say there’s no cause for worry.

“In the past, these swarms last a couple of days to a week or so and then die out,” said Paul Bodin, of the Pacific Northwest Seismic Network at the University of Washington.

The first of the 23 quakes struck on Sept. 11 near the volcano’s summit. The largest of the quakes registered magnitude 1.6.

Earthquake swarms are common at volcanoes, and usually don’t signify any threat of eruption, Bodin said in an email. “So I’m treating this as a single eyebrow raised halfway,” he wrote. “Yeah, I see you and will be watching, but I don’t think you’re going to attack.”

Most volcanic quake swarms originate in the hydrothermal plumbing system, related to slight changes in temperature or groundwater pressure that cause cracking of the rocks, Bodin explained. The recent quakes are shallow, which also suggests they are not connected to the deep movement of magma.

Rainier experienced similar upticks in the past two years, and a more sustained episode of seismicity in 2009.

The Spokesman-Review Newspaper

Local journalism is essential.

Give directly to The Spokesman-Review's Northwest Passages community forums series -- which helps to offset the costs of several reporter and editor positions at the newspaper -- by using the easy options below. Gifts processed in this system are not tax deductible, but are predominately used to help meet the local financial requirements needed to receive national matching-grant funds.

Active Person

Subscribe to the Coronavirus newsletter

Get the day’s latest Coronavirus news delivered to your inbox by subscribing to our newsletter.