QuakeScout
Magnitude3.1

Reviewed by USGSAlaska15y ago

M3.1 earthquake 139 km WSW of Nikolski, Alaska

Monday, November 21, 2011, 06:58:44 UTC · 52.297°N, 170.623°W

A magnitude 3.1 earthquake struck 139 km WSW of Nikolski, Alaska on Monday, November 21, 2011, 06:58:44 UTC, at a depth of 30.9 km (shallow).

Magnitude
3.1
Minor · ml
Depth
31 km
Shallow
Felt reports
0
Did You Feel It?
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

674 kg of TNT

That is about 1/22,353 of the Hiroshima bomb. A magnitude 5.0 releases about 708 times more energy.

Tectonic setting

100 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: shallow

31 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 M3.7 on December 6, 2011. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M41h6h1d3d7d14d30dMainshock M3.1
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 3.4161 km SW of Nikolski, Alaska14y ago · 23 km SW of this epicenter
  2. 3.7131 km WSW of Nikolski, Alaska15y ago · 8 km NE of this epicenter
  3. 2.9178 km WSW of Nikolski, Alaska15y ago · 40 km SW of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 725 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 298 km W of this epicenter
  2. 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 165 km S of this epicenter
  3. 7.881 km E of Nikolski, AlaskaJuly 2, 1965 · 215 km NE of this epicenter
  4. 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 127 km N of this epicenter
  5. 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 87 km W of this epicenter
  6. 7.158 km WNW of Atka, AlaskaFebruary 28, 1970 · 292 km W of this epicenter
  7. 7.135 km SW of Nikolski, AlaskaMarch 11, 1957 · 106 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. The most severe:

  1. 1986M8.0

    Aleutian Islands: Adak

    7 May 1986 · 298 km away · intensity VI

    Moderate damage ($1–5M)tsunami

  2. 1901M7.8

    Aleutian Islands: Fox Islands

    31 Dec 1901 · 98 km away

    Limited damage (under $1M)tsunami

  3. 1965M6.5

    Aleutian Islands: Fox Islands

    2 Jul 1965 · 223 km away

    Limited damage (under $1M)tsunami

  4. 1917M7.9

    Alaska Peninsula

    31 May 1917 · 294 km away · intensity V

  5. 1902M7.8

    Aleutian Islands: Fox Islands

    1 Jan 1902 · 212 km away

  6. 1907M7.8

    Aleutian Islands

    2 Sep 1907 · 69 km away

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

Nearby trackers

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