Mount Rainier's quake swarm breaks seismic records

By the numbers: As of Friday, researchers had analyzed 780 of about 1,200 tremors recorded at the 20 seismic stations on or near the volcano since July 8, according to the Pacific Northwest Seismic Network (PNSN).

• Quake activity was ongoing Monday morning, with seven recorded by 8am.
• The largest among them was a magnitude 2.2 earthquake 1 mile underground.

What they're saying: This is the "most energetic swarm" ever recorded at Mount Rainier, PNSN director Harold Tobin tells Axios, but right now there's no sign of unusual magma activity.

What's happening: Although analysts haven't reviewed every event, all of the larger ones have been checked, says Tobin, and so far, everything about this swarm is consistent with typical hydrothermal activity — hot water and heat circulating through the volcano's plumbing and triggering small fault slips.

What we're watching: Scientists are on the lookout for a number of signs that could show developing unrest, says Tobin, including stronger earthquakes, bulging ground and plumes of steam and gas.