Nearly 20 small earthquakes were detected at Mount Rainier on Wednesday, geologists said.
The swarm of earthquakes began about 3:13 p.m., lasting until around 8 p.m.
The quakes reached a maximum magnitude of 2.5, and at depths between 0 to 1 kilometer (0.6 miles) below sea level, according to the Pacific Northwest Seismic Network.
According to scientists, there were no reports that the quakes were felt at the surface.
“Earthquakes are part of the background activity at Mount Rainier, and swarms of this number of earthquakes typically occur once or twice a year,” the USGS said.
The last time there was a notable swarm of quakes was Sep. 20-22, 2009. There were 1,000 earthquakes detected, scientists said.
“While the seismicity represents a temporary uptick in activity, Mount Rainier remains at normal, background levels of activity.”
According to Michigan Tech, earthquakes that are a magnitude 2.5 or less usually are not felt. Those between 2.5 and 5.4 often are felt, but only cause minor damage.