Overview
- The swarm began on July 8 at 1:29 a.m. local time with hundreds of small quakes recorded at depths of 2–6 km and a maximum magnitude of 1.7.
- It is the most significant earthquake cluster at Mount Rainier since a 2009 event that produced over 1,000 tremors in three days.
- Scientists at the USGS Cascades Volcano Observatory and the Pacific Northwest Seismic Network attribute the quakes to hydrothermal fluid movements rather than magma intrusion.
- No ground deformation, gas anomalies or surface-felt tremors have been detected and both the Volcano Alert Level and Aviation Color Code remain at green.
- Annual swarms beneath the glacier-covered peak fit within its normal background activity and are monitored in real time by a dense network of seismic, infrasound, GPS and webcam stations.