M2.1 earthquake 32 km NNW of Challis, Idaho

A magnitude 2.1 earthquake struck 32 km NNW of Challis, Idaho on Sat, Aug 11, 2018, 11:43 PM MDT (05:43 UTC), 5 km (3 mi) below the surface.

A larger quake followed: M2.8 13 km SE of Challis, Idaho. 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
2.1	ML, local (Richter)	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.069 · 28 stations
2.45	ML, local (Richter)	Montana Bureau of Mines and Geology	Final · ±0.205 · 4 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: 27 in the 60 days after this one and 22 in the 30 days before it.

From the USGS Earthquake Hazards Program and its partner networks, event us1000g74p (also filed as mb80305579). Read Mon, Oct 5, 2026, 3:32 AM UTC.