QuakeScout
Magnitude3.5

Reviewed by USGSAlaska4y ago

M3.5 earthquake 129 km SE of Chignik, Alaska

Wednesday, February 23, 2022, 15:50:02 UTC · 55.420°N, 157.050°W

A magnitude 3.5 earthquake struck 129 km SE of Chignik, Alaska on Wednesday, February 23, 2022, 15:50:02 UTC, at a depth of 45.0 km (shallow).

Magnitude
3.5
Minor · ml
Depth
45 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

3 tons of TNT

That is about 1/5,615 of the Hiroshima bomb. A magnitude 5.0 releases about 178 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

45 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 M2.9 on March 15, 2022. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M31h6h1d3d7d14d30dMainshock M3.5
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 2.9117 km SE of Perryville, Alaska4y ago · 50 km SW of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 358 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.21938 Semidi Islands, Alaska EarthquakeNovember 10, 1938 · 77 km W of this epicenter
  2. 8.22021 Chignik, Alaska EarthquakeJuly 29, 2021 · 53 km W of this epicenter
  3. 7.82020 Perryville, Alaska EarthquakeJuly 22, 2020 · 105 km W of this epicenter
  4. 7.62020 Sand Point, Alaska EarthquakeOctober 19, 2020 · 188 km SW of this epicenter
  5. 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 186 km W of this epicenter
  6. 7.190 km SE of King Cove, AlaskaMay 14, 1948 · 278 km W of this epicenter
  7. 7.14 km ENE of Karluk, AlaskaNovember 7, 1912 · 291 km NE of this epicenter
  8. 7.0113 km ESE of Chignik, AlaskaMay 4, 1923 · 50 km N of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 12 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

  1. 1900M8.3

    Kodiak Island

    9 Oct 1900 · 288 km away · intensity VIII

    Limited damage (under $1M)

  2. 2020M7.8

    Alaska

    22 Jul 2020 · 105 km away · intensity VII

    Limited damage (under $1M)tsunami

  3. 1938M8.2

    Alaska

    10 Nov 1938 · 84 km away · intensity VI

    tsunami

  4. 2021M8.2

    Alaska Peninsula

    29 Jul 2021 · 51 km away · intensity VIII

    tsunami

  5. 1788M8.0

    Alaska Peninsula

    6 Aug 1788 · 255 km away

    tsunami

  6. 1906M7.6

    Aleutian Islands

    23 Dec 1906 · 252 km away

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

Nearby trackers

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