The March 28, 1957 earthquake

M6.8near Unalaska, Alaska

A magnitude 6.8 earthquake 15.5 miles deep, 7.9 miles off Aleutians West Census Area. The 91st strongest in Alaska’s record since 1900, and the strongest within 50 miles in the catalogue, which runs from 1900.

The earthquake

Magnitude: 6.8; moment magnitude (mw)
Depth: 15.5 mi; 25.0 km below the surface
Local time: Thursday, March 28, 1957; 19:10 AST; 05:10 UTC on Mar 29, 1957
Epicentre: 53.31°N, 166.95°W; 7.9 mi from Aleutians West Census Area
In Alaska’s record: 91st; strongest of 124,625 since 1900
Within 50 miles: 1; county; more on this date

USGS ANSS Comprehensive Earthquake Catalog, event iscgem886282 (“68 km SSW of Unalaska, 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 · 7.9 mi

Earthquakes around the epicentre

1,476 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

January 12, 1955M6.8
January 12, 1955M6.5
March 14, 1957M6.4
January 12, 1952M6.3
January 8, 1957M6.2
September 4, 1942M6.2
January 20, 1952M6.2
December 9, 1942M6.2
September 8, 1942M6.2
July 24, 1938M6.1

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