M3.3 earthquake 34 km NNE of Spencer, Idaho

A magnitude 3.3 earthquake struck 34 km NNE of Spencer, Idaho on Wed, Oct 2, 1985, 6:15 AM MDT (12:15 UTC), 5 km (3 mi) below the surface.

A larger quake followed: M3.4 2 km ESE of West Yellowstone, 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.

Reviewed by a seismologist.

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

Within 100 km, magnitude 1.5 and up: 149 in the 60 days after this one and 3 in the 30 days before it.

The first 60 of 149.

From the USGS Earthquake Hazards Program and its partner networks, event usp0002kcv. Read Tue, Sep 22, 2026, 10:18 AM UTC.