Officials are tracking an earthquake swarm at Mount Rainier but say there is no cause for concern

SEATTLE — Officials are tracking the largest swarm of earthquakes in more than 15 years on Washington's Mount Rainier but say there is no indication that the cluster of quakes is cause for concern.

The U.S. Geological Survey Cascades Volcano Observatory said the swarm began early Tuesday at the 14,410-foot (4,392-meter) volcano near Seattle. The swarm has consisted of hundreds of small earthquakes — the largest of which so far has been a magnitude 2.3 — and has surpassed a 2009 swarm in terms of magnitude, event rate, total events and energy release, the agency said in a statement Thursday.

The cause of the current swarm is consistent with the circulation of fluids along preexisting faults beneath the volcano and considered “background activity” at Mount Rainier, the agency said. The volcano alert level remained at normal, and the earthquakes have been too small to be felt at the surface, the agency said.

Swarms can occur once or twice at year at Mount Rainier, though the number of quakes involved are usually smaller, the volcano observatory said.

Mount Rainier, about 60 miles (97 kilometers) southeast of Seattle, is the most glaciated peak in the Lower 48 states.