Earthquake swarm: Hundreds recorded Tuesday at WA's Mount Rainier
Hundreds of Earthquakes from Mt. Rainier
The U.S. Geological Survey and the Pacific Northwest Seismic Network said there is no reason for concern based on this earthquake activity.
MOUNT RAINIER, Wash. - Mount Rainier on Tuesday experienced its largest seismic activity since 2009, with a swarm of small earthquakes detected. According to the United States Geological Survey, hundreds of earthquakes were recorded.
What we know:
The tremors began around 1:30 a.m. PST and ranged in magnitude from 0.1 to 1.7. None have been felt at the surface and more are expected throughout the day.
The earthquakes are all at a depth of 1 to 4 miles below the surface within the area of Mount Rainier itself.
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"At present, 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," said Harold Tobin, Director of Pacific Northwest Seismic Network.
Map of small earthquakes recorded on Mount Rainier on July 8, 2025. (Pacific Northwest Seismic Netowrk)
Earthquakes happen nearly every day in Washington, according to the Department of Natural Resources, and Mount Rainier is one of the most seismically active volcanoes in the Washington and Oregon Cascades.
FILE - Mount Rainier viewed from the Longmire Viewpoint on the Wonderland Trail in Mt Rainier National Park on Tuesday, June 28 2022. (Thomas O'Neill/NurPhoto via Getty Images)
The U.S. Geological Survey notes that earthquakes frequently happen on Mount Rainier. The PNSN records 3 to 4 earthquakes within 3 miles of the summit in an average month.
The largest recorded earthquake beneath Mount Rainier was a magnitude 3.9 in 1973. Earthquakes with a magnitude of over 3.0 also occurred in 1976, 1990, 2002 and 2004.
What's an earthquake swarm?
Earthquake swarms, defined as three or more small earthquakes in a single day, are rare but do occur. The most notable swarm happened between Sept. 20-22, 2009, when more than 1,000 earthquakes were detected, of which the PNSN officially located 120 earthquakes.
Tobin said they typically are associated with movement of fluids (most likely, hydrothermal water) interacting with small faults within the volcano.
"We have no reason to suspect magma activity at this time," Tobin said.
USGS and PNSN are continuing to monitor the seismic activity.
The Source: Information in this story came from the Pacific Northwest Seismic Network, the United States Geologic Survey, Washington State Department of Natural Resources and original reporting by FOX 13 Seattle.
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