The December 21, 1917 earthquake

M6.6near Old Harbor, Alaska

A magnitude 6.6 earthquake 9.3 miles deep, 39.8 miles off Kodiak Island Borough. The 145th strongest in Alaska’s record since 1900, and the strongest within 50 miles in the catalogue, which runs from 1900.

The earthquake

Magnitude: 6.6; moment magnitude (mw)
Depth: 9.3 mi; 15.0 km below the surface
Local time: Friday, December 21, 1917; 07:54 AST; 17:54 UTC
Epicentre: 56.45°N, 152.84°W; 39.8 mi from Kodiak Island Borough
In Alaska’s record: 145th; strongest of 124,625 since 1900
Within 50 miles: 1; county; more on this date

USGS ANSS Comprehensive Earthquake Catalog, event iscgem913730 (“88 km SSE of Old Harbor, 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

Kodiak Island BoroughAK · 39.8 mi

Earthquakes around the epicentre

498 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.