The March 27, 1940 earthquake

M6.6near Adak, Alaska

A magnitude 6.6 earthquake 31.1 miles deep, 2.4 miles off Aleutians West Census Area. The 173rd strongest in Alaska’s record since 1900, and the strongest within 50 miles since a magnitude 6.7 on April 26, 1930.

The earthquake

Magnitude: 6.6; moment magnitude (mw)
Depth: 31.1 mi; 50.0 km below the surface
Local time: Wednesday, March 27, 1940; 01:31 NST; 12:31 UTC
Epicentre: 51.43°N, 179.43°E; 2.4 mi from Aleutians West Census Area
In Alaska’s record: 173rd; strongest of 124,625 since 1900
Within 50 miles: 1; county; more on this date

USGS ANSS Comprehensive Earthquake Catalog, event iscgem901254 (“276 km WSW of Adak, Alaska”). 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

Aleutians West Census AreaAK · 2.4 mi

Earthquakes around the epicentre

2,894 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

March 21, 1905M7.2
February 6, 1916M7.0
March 30, 1913M6.9
October 12, 1926M6.7
April 26, 1930M6.7
October 13, 1926M6.7
May 20, 1930M6.5
February 2, 1930M6.5
August 15, 1915M6.4
July 14, 1919M6.2

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