M7.3 earthquake in Fox Islands, Aleutian Islands, Alaska

Friday, June 24, 2011, 03:09:39 UTC · 52.050°N, 171.836°W

A magnitude 7.3 earthquake struck in Fox Islands, Aleutian Islands, Alaska on Friday, June 24, 2011, 03:09:39 UTC, at a depth of 52.0 km (shallow). USGS received 29 “Did You Feel It?” reports, with a maximum reported intensity of VI (strong). It is the strongest earthquake within 300 km since an M8.0 on May 7, 1986.

Magnitude: 7.3; Major · mww
Depth: 52 km; Shallow
Felt reports: 29; Max intensity VI
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

1.3 megatons of TNT

That is about 89 times the Hiroshima bomb. It released about 2,818 times the energy of a magnitude 5.0.

Tectonic setting

97 km

from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: shallow

52 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

Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.

Place	Intensity	Reports	Distance
99692<br>0.302	III · Weak	4	363 km
99638<br>0.311	VI · Strong	3	250 km
99685<br>0.320	IV · Light	2	401 km
99503<br>0.330	V · Moderate	1	1689 km
99546<br>0.330	IV · Light	1	339 km
99603<br>0.330	III · Weak	1	1540 km
99501<br>0.330	II · Weak	1	1691 km
99515<br>0.330	II · Weak	1	1685 km
99506<br>0.330	II · Weak	1	1697 km
99571<br>0.330	II · Weak	1	816 km

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 266 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.8 on June 28, 2011. 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 775 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 13 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 2 recorded deaths. The most severe:

1957M8.6
Alaska
9 Mar 1957 · 268 km away
2 deathsSevere damage ($5–24M)tsunami
1986M8.0
Aleutian Islands: Adak
7 May 1986 · 211 km away · intensity VI
Moderate damage ($1–5M)tsunami
1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 87 km away
Limited damage (under $1M)tsunami
1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 298 km away
1907M7.8
Aleutian Islands
2 Sep 1907 · 155 km away
1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 173 km away · intensity V
tsunami

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

Nearby trackers