QuakeScout
Magnitude3.7

Reviewed by USGSAlaska2y ago

M3.7 earthquake 155 km S of Unalaska, Alaska

Wednesday, September 18, 2024, 05:42:47 UTC · 52.492°N, 166.201°W

A magnitude 3.7 earthquake struck 155 km S of Unalaska, Alaska on Wednesday, September 18, 2024, 05:42:47 UTC, at a depth of 10.0 km (shallow).

Magnitude
3.7
Minor · mb
Depth
10 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

5 tons of TNT

That is about 1/2,814 of the Hiroshima bomb. A magnitude 5.0 releases about 89 times more energy.

Tectonic setting

7 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 M3.9 on October 15, 2024. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M41h6h1d3d7d14d30dMainshock M3.7
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 3.9141 km ESE of Nikolski, Alaska1y ago · 46 km W of this epicenter
  2. 3.0161 km S of Unalaska, Alaska2y ago · 28 km W of this epicenter
  3. 3.0158 km S of Unalaska, Alaska2y ago · 4 km SE of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 652 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.6The 1946 Unimak Island, Alaska EarthquakeApril 1, 1946 · 251 km NE of this epicenter
  2. 7.881 km E of Nikolski, AlaskaJuly 2, 1965 · 113 km NW of this epicenter
  3. 7.139 km S of Akutan, AlaskaMarch 22, 1957 · 146 km N of this epicenter
  4. 7.135 km SW of Nikolski, AlaskaMarch 11, 1957 · 203 km W of this epicenter
  5. 7.0203 km SSE of Unalaska, AlaskaAugust 22, 1940 · 60 km SE of this epicenter
  6. 6.980 km SW of Nikolski, AlaskaMarch 9, 1957 · 227 km W of this epicenter
  7. 6.977 km SSW of Nikolski, AlaskaJanuary 23, 1935 · 219 km W of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 11 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 168 recorded deaths. The most severe:

  1. 1946M8.6

    Unimak Island

    1 Apr 1946 · 251 km away · intensity VI

    168 deaths$26 million damagetsunami

  2. 1965M6.5

    Aleutian Islands: Fox Islands

    2 Jul 1965 · 109 km away

    Limited damage (under $1M)tsunami

  3. 1902M7.8

    Aleutian Islands: Fox Islands

    1 Jan 1902 · 89 km away

  4. 1907M7.8

    Aleutian Islands

    2 Sep 1907 · 239 km away

  5. 1916M7.5

    Aleutian Islands: Fox Islands

    18 Apr 1916 · 270 km away

  6. 1957M7.5

    Aleutian Islands: Fox Islands

    22 Mar 1957 · 287 km away · intensity V

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

Nearby trackers

Closest city pages