Montana earthquakes

M1.9 earthquake 21 km SSW of Mammoth, Wyoming

A magnitude 1.9 earthquake struck 21 km SSW of Mammoth, Wyoming on Fri, Mar 1, 1985, 9:46 PM MST (04:46 UTC), 11 km (7 mi) below the surface.

A larger quake followed: M3.6 23 km SSW of Mammoth, Wyoming. This one was a foreshock.

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Map

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

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The earthquake

Magnitude
1.9 (md), micro
Local time
UTC
1985-03-02 04:46:23 UTC
Depth
11.0 km (6.8 mi), shallow
Epicenter
44.798° N, 110.790° W
Region
Montana
Tsunami flag
No
Status
Reviewed by a seismologist

Did you feel it?

No one has reported feeling this quake to the USGS.

How well it is located

Reviewed by a seismologist.

Location uncertainty
About 0.8 km horizontally, 1.0 km in depth
Depth from
From location
Station coverage gap
112°
Stations used
22

Nearest places

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

Nearby

Within 100 km, magnitude 1.5 and up: 9 in the 60 days after this one and 5 in the 30 days before it.

After

  1. 1.620 km SSW of Mammoth, Wyoming · 15179 days ago · 6 km deep · 1 km away
  2. 1.620 km SSW of Mammoth, Wyoming · 15179 days ago · 5 km deep · 3 km away
  3. 3.623 km SSW of Mammoth, Wyoming · 15176 days ago · 5 km deep · 3 km away
  4. 3.223 km S of Mammoth, Wyoming · 15176 days ago · 5 km deep · 9 km away
  5. 2.319 km SSW of Mammoth, Wyoming · 15171 days ago · 28 km deep · 2 km away
  6. 3.529 km W of Hebgen Lake Estates, Montana · 15161 days ago · 5 km deep · 61 km away
  7. 2.041 km SSE of Mammoth, Wyoming · 15138 days ago · 2 km deep · 32 km away
  8. 1.821 km SSW of Mammoth, Wyoming · 15124 days ago · 12 km deep · 2 km away
  9. 1.9Idaho-Montana border region · 15120 days ago · 12 km deep · 42 km away

Before

  1. 2.420 km SSW of Mammoth, Wyoming · 15179 days ago · 12 km deep · 1 km away
  2. 1.520 km SSW of Mammoth, Wyoming · 15179 days ago · 5 km deep · 1 km away
  3. 2.820 km SSW of Mammoth, Wyoming · 15180 days ago · 12 km deep · 1 km away
  4. 2.520 km SSW of Mammoth, Wyoming · 15180 days ago · 11 km deep · 1 km away
  5. 1.835 km E of West Yellowstone, Montana · 15184 days ago · 3 km deep · 24 km away

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Sources

From the USGS Earthquake Hazards Program and its partner networks, event uu50019690 (also filed as usp0002cbg). Read Tue, Sep 22, 2026, 12:18 PM UTC.