M6.9 earthquake in Fox Islands, Aleutian Islands, Alaska

Monday, July 27, 2015, 04:49:46 UTC · 52.376°N, 169.446°W

A magnitude 6.9 earthquake struck in Fox Islands, Aleutian Islands, Alaska on Monday, July 27, 2015, 04:49:46 UTC, at a depth of 29.0 km (shallow). USGS received 3 “Did You Feel It?” reports, with a maximum reported intensity of IV (light). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M6.9 on September 2, 2011.

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: 6.9; Strong · mww
Depth: 29 km; Shallow
Felt reports: 3; Max intensity IV
Est. shaking: VII; Very strong (ShakeMap)
PAGER alert: Green; Impact estimate
Tsunami: Flag; Check tsunami.gov

Outlined circle: this earthquakeDashed circle: 100 km aftershock search area

In context

How big was it, and why here?

Energy released

338 kilotons of TNT

That is about 22 times the Hiroshima bomb. It released about 708 times the energy of a magnitude 5.0.

Tectonic setting

77 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

29 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
99685<br>0.320	IV · Light	2	247 km
99669<br>0.330	II · Weak	1	1448 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 100 km

USGS lists 393 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M5.9 on July 27, 2015. 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 634 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. The most severe:

1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 149 km away
Limited damage (under $1M)tsunami
1965M6.5
Aleutian Islands: Fox Islands
2 Jul 1965 · 147 km away
Limited damage (under $1M)tsunami
1917M7.9
Alaska Peninsula
31 May 1917 · 269 km away · intensity V
1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 132 km away
1907M7.8
Aleutian Islands
2 Sep 1907 · 31 km away
1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 158 km away · intensity V
tsunami

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

Nearby trackers