The November 23, 1947 earthquake
M6.1near Big Sky, Montana
A magnitude 6.1 earthquake 9.3 miles deep, centred in Madison County. The 5th strongest in Montana’s record since 1900, and the strongest within 50 miles in the catalogue, which runs from 1900.
The earthquake
- Magnitude
- 6.1
- moment magnitude (mw)
- Depth
- 9.3 mi
- 15.0 km below the surface
- Local time
- Sunday, November 23, 1947
- 02:46 MST; 09:46 UTC
- In Montana’s record
- 5th
- strongest of 1,459 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event iscgem898156 (“30 km SSW of Big Sky, Montana”). The USGS event page carries the ShakeMap, felt reports and the official summary.
Counties and cities within 50 miles
Distance from the epicentre to each county boundary (zero when inside) and to each city centre.
Counties
- Madison CountyMT · inside
- Beaverhead CountyMT · 21.4 mi
- Fremont CountyID · 21.8 mi
- Gallatin CountyMT · 22.2 mi
- Park CountyWY · 24.7 mi
- Park CountyMT · 25.1 mi
- Clark CountyID · 34.4 mi
- Teton CountyWY · 36.0 mi
Earthquakes around the epicentre
401 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.
No earlier earthquake of magnitude 5 or more within 50 miles in the catalogue since 1900.
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.