Hundreds of tiny earthquakes have hit the Mammoth Lakes area in California's Eastern Sierra in recent days, according to the U.S. Geological Survey.
Most of the quakes were less than magnitude 1.0 — and it's likely that none were felt by residents.
There were several dozen quakes in just the last 24 hours, the strongest being 2.3 magnitude. More quakes continued into Sunday.
Earthquake swarms are not uncommon in the region.
Countless small faults crisscross an area known as the Long Valley Caldera, a roughly 20-mile-wide crater-like depression adjacent to Mammoth Mountain that was formed from ash and pumice deposits during a volcanic "super eruption" about 760,000 years ago.
Noted seismologist Lucy Jones tweeted about the quake swarm swarm on Thursday, saying: "Swarms are very common in Mammoth area and don't impact SoCal risk."