The July 10, 1925 earthquake

M5.5Clarkston Valley, Montana (Aftershock)

A magnitude 5.5 earthquake, centred in Broadwater County. The 12th strongest in Montana’s record since 1900, and the strongest within 50 miles since a magnitude 5.5 on June 27, 1925.

The earthquake

Magnitude: 5.5; as reported (mfa)
Depth: —; Not recorded
Local time: Friday, July 10, 1925; 07:42 MST; 14:42 UTC
Epicentre: 46.08°N, 111.51°W; In Broadwater County
In Montana’s record: 12th; strongest of 1,459 since 1900
Within 50 miles: 9; counties; more on this date

USGS ANSS Comprehensive Earthquake Catalog, event mb19250710144200000 (“Clarkston Valley, Montana (Aftershock)”). 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

Broadwater CountyMT · inside
Gallatin CountyMT · 4.3 mi
Jefferson CountyMT · 7.5 mi
Meagher CountyMT · 22.7 mi
Madison CountyMT · 23.4 mi
Lewis and Clark CountyMT · 34.3 mi
Park CountyMT · 35.6 mi
Silver Bow CountyMT · 39.9 mi
Powell CountyMT · 44.9 mi

Cities, largest first

BozemanMT · 35.1 mi
HelenaMT · 43.1 mi
BelgradeMT · 26.0 mi

Earthquakes around the epicentre

151 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.

Earlier earthquakes of magnitude 5 or more within 50 miles, strongest first

USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.