M1.8 earthquake 22 km SSW of Mammoth, Wyoming

A magnitude 1.8 earthquake struck 22 km SSW of Mammoth, Wyoming on Fri, Mar 19, 2021, 9:13 AM MDT (15:13 UTC), 4 km (3 mi) below the surface.

A larger quake followed: M2.5 23 km NE of West Yellowstone, Montana. This one was a foreshock.

Map

Where this earthquake was located, with the others nearby. Select one for its page.

Different scales measure different things and differ by a few tenths. The USGS marks one as preferred, and it is the one this page uses.

Mag.	Scale	Computed by	Notes
1.8	Md, duration	University of Utah Seismograph Stations	Preferred · Final · ±0.243 · 10 stations
1.91	ML, local (Richter)	Montana Bureau of Mines and Geology	Final · ±0.204 · 9 stations

No one has reported feeling this quake to the USGS.

Reviewed by a seismologist.

Distance and direction from each place to the epicenter, with its forecast.

Within 100 km, magnitude 1.5 and up: 20 in the 60 days after this one and 18 in the 30 days before it.

From the USGS Earthquake Hazards Program and its partner networks, event uu60429692 (also filed as mb80492239). Read Sun, Oct 4, 2026, 11:04 PM UTC.