M2.5 earthquake 17 km SSE of Harrison, Montana

A magnitude 2.5 earthquake struck 17 km SSE of Harrison, Montana on Wed, Jul 22, 1987, 2:26 AM MDT (08:26 UTC), 3 km (2 mi) below the surface.

A larger quake followed: M3.1 17 km SSE of Harrison, Montana. This one was a foreshock.

Map

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

No one has reported feeling this quake to the USGS.

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

Within 100 km, magnitude 1.5 and up: 29 in the 60 days after this one and 15 in the 30 days before it.

From the USGS Earthquake Hazards Program and its partner networks, event usp00036v2. Read Tue, Sep 22, 2026, 10:58 AM UTC.