QuakeScout
Magnitude2.8

Reviewed by USGSAlaska15y ago

M2.8 earthquake 97 km E of Atka, Alaska

Wednesday, August 17, 2011, 02:11:03 UTC · 52.071°N, 172.796°W

A magnitude 2.8 earthquake struck 97 km E of Atka, Alaska on Wednesday, August 17, 2011, 02:11:03 UTC, at a depth of 67.9 km (shallow).

Magnitude
2.8
Minor · ml
Depth
68 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

239 kg of TNT

That is about 1/63,000 of the Hiroshima bomb. A magnitude 5.0 releases about 1,995 times more energy.

Tectonic setting

113 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

68 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 M4.1 on August 27, 2011. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M41h6h1d3d7d14d30dMainshock M2.8
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 3.477 km ESE of Atka, Alaska15y ago · 37 km SW of this epicenter
  2. 3.4139 km E of Atka, Alaska15y ago · 43 km E of this epicenter
  3. 4.1110 km ESE of Atka, Alaska15y ago · 15 km SE of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 853 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.61957 Atka, Alaska EarthquakeMarch 9, 1957 · 205 km W of this epicenter
  2. 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 149 km SW of this epicenter
  3. 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 245 km SE of this epicenter
  4. 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 268 km W of this epicenter
  5. 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 209 km NE of this epicenter
  6. 7.346 km SSW of Adak, AlaskaJune 10, 1996 · 286 km W of this epicenter
  7. 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 66 km E of this epicenter
  8. 7.175 km S of Adak, AlaskaMarch 14, 1957 · 289 km W of this epicenter

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, which together caused about 2 recorded deaths. The most severe:

  1. 1957M8.6

    Alaska

    9 Mar 1957 · 205 km away

    2 deathsSevere damage ($5–24M)tsunami

  2. 1986M8.0

    Aleutian Islands: Adak

    7 May 1986 · 149 km away · intensity VI

    Moderate damage ($1–5M)tsunami

  3. 1901M7.8

    Aleutian Islands: Fox Islands

    31 Dec 1901 · 140 km away

    Limited damage (under $1M)tsunami

  4. 1907M7.8

    Aleutian Islands

    2 Sep 1907 · 216 km away

  5. 1929M7.8

    Aleutian Islands: Fox Islands

    7 Mar 1929 · 227 km away · intensity V

    tsunami

  6. 1916M7.5

    Aleutian Islands: Fox Islands

    18 Apr 1916 · 233 km away

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

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