M7.2 earthquake 207 km WSW of Adak, Alaska

Wednesday, December 19, 2007, 09:30:27 UTC · 51.360°N, 179.509°W

A magnitude 7.2 earthquake struck 207 km WSW of Adak, Alaska on Wednesday, December 19, 2007, 09:30:27 UTC, at a depth of 34.0 km (shallow). USGS received 5 “Did You Feel It?” reports, with a maximum reported intensity of II (weak). It is the strongest earthquake within 300 km since an M7.8 on November 17, 2003.

Magnitude: 7.2; Major · mwc
Depth: 34 km; Shallow
Felt reports: 5; Max intensity II
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

951 kilotons of TNT

That is about 63 times the Hiroshima bomb. It released about 1,995 times the energy of a magnitude 5.0.

Tectonic setting

95 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

34 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
99611<br>0.330	II · Weak	1	2089 km
99567<br>0.330	II · Weak	1	2176 km
99645<br>0.330	II · Weak	1	2254 km
99669<br>0.330	II · Weak	1	2049 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 254 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.3 on December 21, 2007. 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 940 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 12 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 · 270 km away
2 deathsSevere damage ($5–24M)tsunami
1965M8.7
Aleutian Islands: Rat Islands
4 Feb 1965 · 124 km away · intensity VI
Under $1 million damagetsunami
1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 169 km away
1905M7.9
Andreanof Islands
14 Feb 1905 · 97 km away
1996M7.9
Andreanof Islands
10 Jun 1996 · 132 km away · intensity VI
tsunami
2003M7.8
Aleutian Islands: Rat Islands
17 Nov 2003 · 130 km away
tsunami

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

Nearby trackers