Reviewed by USGSAlaska11y ago
M2.9 earthquake 178 km ESE of Atka, Alaska
Saturday, October 31, 2015, 01:16:22 UTC · 51.831°N, 171.674°W
A magnitude 2.9 earthquake struck 178 km ESE of Atka, Alaska on Saturday, October 31, 2015, 01:16:22 UTC, at a depth of 10.0 km (shallow).
- Magnitude
- 2.9
- Minor · ml
- Depth
- 10 km
- Shallow
- Felt reports
- 0
- Max intensity I
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
338 kg of TNT
That is about 1/44,601 of the Hiroshima bomb. A magnitude 5.0 releases about 1,413 times more energy.
Tectonic setting
71 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
10 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 50 km
USGS lists 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M2.9 on November 28, 2015. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 854 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.61957 Atka, Alaska EarthquakeMarch 9, 1957 · 275 km W of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 217 km W of this epicenter
- 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 167 km SE of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 192 km N of this epicenter
- 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 27 km NW of this epicenter
- 7.158 km WNW of Atka, AlaskaFebruary 28, 1970 · 233 km W of this epicenter
- 7.135 km SW of Nikolski, AlaskaMarch 11, 1957 · 194 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 14 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 · 275 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 217 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 62 km away
Limited damage (under $1M)tsunami
- 1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 292 km away
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 157 km away
- 1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 148 km away · intensity V
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.