M7.0 earthquake 71 km SE of King Cove, Alaska

Thursday, May 30, 1991, 13:17:41 UTC · 54.567°N, 161.606°W

A magnitude 7.0 earthquake struck 71 km SE of King Cove, Alaska on Thursday, May 30, 1991, 13:17:41 UTC, at a depth of 28.4 km (shallow). It is the strongest earthquake within 300 km since an M7.1 on March 22, 1957.

Magnitude: 7.0; Major · mw
Depth: 28 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: —; No ShakeMap
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 200 km aftershock search area

In context

How big was it, and why here?

Energy released

477 kilotons of TNT

That is about 32 times the Hiroshima bomb. It released about 1,000 times the energy of a magnitude 5.0.

Tectonic setting

113 km

from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: shallow

28 km

Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.

Did You Feel It?

Where it was felt

No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.

I felt it — report to USGS ↗

USGS PAGER estimate

Who was exposed to shaking

USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.

After the main event

Aftershocks within 200 km

USGS lists 18 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.6 on May 30, 1991. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 194 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 7 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 168 recorded deaths. The most severe:

1946M8.6
Unimak Island
1 Apr 1946 · 144 km away · intensity VI
168 deaths$26 million damagetsunami
1938M8.2
Alaska
10 Nov 1938 · 230 km away · intensity VI
tsunami
1788M8.0
Alaska Peninsula
6 Aug 1788 · 62 km away
tsunami
1948M7.5
Alaska Peninsula
14 May 1948 · 40 km away
1957M7.5
Aleutian Islands: Fox Islands
22 Mar 1957 · 235 km away · intensity V
1820
East Aleutian Islands
1 Mar 1820 · 196 km away
tsunami

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers