QuakeScout
Magnitude3.8

Reviewed by USGSAlaska5y ago

M3.8 earthquake 140 km S of False Pass, Alaska

Wednesday, June 16, 2021, 18:14:11 UTC · 53.590°N, 163.507°W

A magnitude 3.8 earthquake struck 140 km S of False Pass, Alaska on Wednesday, June 16, 2021, 18:14:11 UTC, at a depth of 35.0 km (shallow).

Magnitude
3.8
Minor · mb
Depth
35 km
Shallow
Felt reports
0
Did You Feel It?
Est. shaking
I
Not felt (ShakeMap)
PAGER alert
None
Not issued
Tsunami
No flag
USGS feed

Outlined circle: this earthquakeDashed circle: 50 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

8 tons of TNT

That is about 1/1,992 of the Hiroshima bomb. A magnitude 5.0 releases about 63 times more energy.

Tectonic setting

50 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

35 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 M3.8 on July 6, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M41h6h1d3d7d14d30dMainshock M3.8
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 2.5156 km S of False Pass, Alaska5y ago · 15 km S of this epicenter
  2. 3.8141 km S of False Pass, Alaska5y ago · 8 km W of this epicenter
  3. 2.8145 km S of False Pass, Alaska5y ago · 4 km S of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 448 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 · 46 km E of this epicenter
  2. 7.881 km E of Nikolski, AlaskaJuly 2, 1965 · 283 km W of this epicenter
  3. 7.62020 Sand Point, Alaska EarthquakeOctober 19, 2020 · 277 km NE of this epicenter
  4. 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 282 km NE of this epicenter
  5. 7.190 km SE of King Cove, AlaskaMay 14, 1948 · 189 km NE of this epicenter
  6. 7.139 km S of Akutan, AlaskaMarch 22, 1957 · 151 km W of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 10 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 · 46 km away · intensity VI

    168 deaths$26 million damagetsunami

  2. 1965M6.5

    Aleutian Islands: Fox Islands

    2 Jul 1965 · 276 km away

    Limited damage (under $1M)tsunami

  3. 1788M8.0

    Alaska Peninsula

    6 Aug 1788 · 226 km away

    tsunami

  4. 1902M7.8

    Aleutian Islands: Fox Islands

    1 Jan 1902 · 298 km away

  5. 2020M7.6

    Alaska

    19 Oct 2020 · 277 km away · intensity IX

    tsunami

  6. 1948M7.5

    Alaska Peninsula

    14 May 1948 · 192 km away

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

Nearby trackers

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