Hundreds of small earthquakes recorded in Mount Rainier swarm for first time since 2009
PORTLAND, Ore. (KOIN) — Hundreds of small earthquakes have been detected at Mount Rainier in Washington in an earthquake swarm, the largest number seen in more than 15 years, according to geologists.
The U.S. Geological Survey says the Cascades Volcano Observatory and Pacific Northwest Seismic Network at the University of Washington started to detect the earthquakes just before 1:30 a.m. on Tuesday.
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The earthquakes are currently numbering in the “several hundred small events,” with the largest one reaching a 1.7-magnitude and the earthquakes hitting at depths of between 1.2 and 3.7 miles.
“Earthquake swarms are relatively common at Mount Rainier, typically occurring 1–2 times per year but usually with many fewer events than have been detected so far during the current swarm,” officials with USGS said in a post on its USGS Volcanoes Facebook page.
The last time Mount Rainier saw a significant swarm of volcanoes was in 2009, when the mountain saw more than 1,000 earthquakes in a three-day period, with the largest clocking a magnitude of 2.3.
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So what’s the cause of these earthquakes on Mount Rainier?
“Earthquake swarms like this have been attributed to circulation of hydrothermal fluids that are interacting with preexisting faults at shallow levels below the summit of the volcano,” according to USGS.
Mount Rainier’s GPS stations have not recorded any changes in ground deformation, which is a warning sign for potential eruption.
Mount Rainier, which has the tallest Cascade Range peak at 14,409 feet, is listed as an “active, ice-clad stratovolcano,” with strong geologic evidence of an eruption about 1,000 years ago.
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