QuakeScout
Magnitude2.7

Reviewed by USGSAlaska22y ago

M2.7 earthquake 52 km S of Atka, Alaska

Sunday, September 19, 2004, 21:31:52 UTC · 51.724°N, 174.209°W

A magnitude 2.7 earthquake struck 52 km S of Atka, Alaska on Sunday, September 19, 2004, 21:31:52 UTC, at a depth of 20.0 km (shallow).

Magnitude
2.7
Minor · ml
Depth
20 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

169 kg of TNT

That is about 1/88,990 of the Hiroshima bomb. A magnitude 5.0 releases about 2,818 times more energy.

Tectonic setting

91 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

20 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 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M3.2 on September 28, 2004. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M31h6h1d3d7d14d30dMainshock M2.7
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 3.246 km S of Atka, Alaska22y ago · 9 km NE of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 803 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 · 101 km W of this epicenter
  2. 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 45 km SW of this epicenter
  3. 7.977 km WSW of Adak, AlaskaJune 10, 1996 · 237 km W of this epicenter
  4. 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 172 km W of this epicenter
  5. 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 246 km W of this epicenter
  6. 7.346 km SSW of Adak, AlaskaJune 10, 1996 · 184 km W of this epicenter
  7. 7.175 km S of Adak, AlaskaMarch 14, 1957 · 184 km W of this epicenter
  8. 7.160 km SW of Adak, AlaskaMarch 12, 1957 · 211 km W of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 8 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 · 101 km away

    2 deathsSevere damage ($5–24M)tsunami

  2. 1986M8.0

    Aleutian Islands: Adak

    7 May 1986 · 45 km away · intensity VI

    Moderate damage ($1–5M)tsunami

  3. 1901M7.8

    Aleutian Islands: Fox Islands

    31 Dec 1901 · 222 km away

    Limited damage (under $1M)tsunami

  4. 1996M7.9

    Andreanof Islands

    10 Jun 1996 · 237 km away · intensity VI

    tsunami

  5. 1996M7.3

    Andreanof Islands

    10 Jun 1996 · 184 km away

    tsunami

  6. 1971M7.1

    Andreanof Islands

    2 May 1971 · 210 km away · intensity VI

    tsunami

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

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