M7.9 earthquake in Rat Islands, Aleutian Islands, Alaska

Monday, June 23, 2014, 20:53:09 UTC · 51.849°N, 178.735°E

A magnitude 7.9 earthquake struck in Rat Islands, Aleutian Islands, Alaska on Monday, June 23, 2014, 20:53:09 UTC, at a depth of 109.0 km (intermediate). USGS received 5 “Did You Feel It?” reports, with a maximum reported intensity of VI (strong). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M7.9 on June 10, 1996.

Tsunami flagUSGS sets this flag for large events in oceanic regions so tsunami warning centers review them. It does not by itself mean a tsunami occurred. Check tsunami.gov and local authorities for official messages.

Magnitude: 7.9; Major · mww
Depth: 109 km; Intermediate
Felt reports: 5; Max intensity VI
Est. shaking: VIII; Severe (ShakeMap)
PAGER alert: Green; Impact estimate
Tsunami: Flag; Check tsunami.gov

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

In context

How big was it, and why here?

Energy released

11 megatons of TNT

That is about 709 times the Hiroshima bomb. It released about 22,387 times the energy of a magnitude 5.0.

Tectonic setting

137 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: intermediate

109 km

Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.

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
99546<br>0.330	VI · Strong	1	332 km
99517<br>0.330	II · Weak	1	2193 km
99664<br>0.330	II · Weak	1	2217 km
99750<br>0.330	II · Weak	1	2037 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 populated area was estimated to feel noticeable shaking.

After the main event

Aftershocks within 200 km

USGS lists 594 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.3 on June 24, 2014. 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 894 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. The most severe:

1965M8.7
Aleutian Islands: Rat Islands
4 Feb 1965 · 66 km away · intensity VI
Under $1 million damagetsunami
1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 38 km away
1905M7.9
Andreanof Islands
14 Feb 1905 · 226 km away
1996M7.9
Andreanof Islands
10 Jun 1996 · 252 km away · intensity VI
tsunami
2014M7.9
Aleutian Islands
23 Jun 2014 · 0 km away · intensity VI
tsunami
1909M7.8
Aleutian Islands
10 Apr 1909 · 257 km away

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

Nearby trackers