M2.4 earthquake 14 km NW of Challis, Idaho

A magnitude 2.4 earthquake struck 14 km NW of Challis, Idaho on Tue, Mar 20, 2018, 10:32 AM MDT (16:32 UTC), 5 km (3 mi) below the surface.

A larger quake followed: M2.5 14 km WNW of Clayton, 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
2.4	ML, local (Richter)	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.071 · 26 stations
2.68	ML, local (Richter)	Montana Bureau of Mines and Geology	Final · ±0.12 · 8 stations

2 people reported to the USGS what they felt; the strongest reported shaking was III, weak shaking.

Reviewed by a seismologist.

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

Within 100 km, magnitude 1.5 and up: 28 in the 60 days after this one and 11 in the 30 days before it.

From the USGS Earthquake Hazards Program and its partner networks, event us1000d71r (also filed as mb80286584). Read Sun, Oct 4, 2026, 7:41 AM UTC.