Hundreds of earthquakes detected at Washington’s Mt. Rainier

A swarm of hundreds of small earthquakes has been detected rumbling deep below Mt. Rainier in Washington State early Tuesday morning, though geologists stress there is no cause for concern.

The quakes began just before 1:30 a.m. and have been occurring at a rate of several times per minute, said officials with the US Geological Survey at the Cascade Volcano Observatory.

All the quakes have been occurring between 1.2 and 3.7 miles beneath the summit, and have been small in magnitude.

The largest quake measured so far is 1.7, and none have been felt at the surface.

According to the USGS, quake swarms occur a couple of times a year, on average, under the state’s tallest volcano, though this one is a bit unusual in terms of the number of quakes.

“Currently, there is no indication that the level of earthquake activity is cause for concern, and the alert level and color code for Mount Rainier remain at (Green/Normal),” the USGS wrote in a Tuesday morning press release.  “Instruments do not show any detectable ground deformation at the volcano, and no anomalous signals have been seen on the infrasound monitoring stations.”

Past swarms have been attributed to the circulation of floods interacting with preexisting faults, the USGS said.

Mt. Rainier will experience about nine quakes in a typical month.

The last big quake swarm was in 2009 and measured over 1,000 quakes over three days, peaking at magnitude 2.3.Mt. Rainier is the closest volcano to the Puget Sound metro area, nestled about 45 miles southeast of Tacoma and 60 miles southeast of Seattle.

Geological records last indicate Rainier erupted about 1,000 years ago.