QuakeScout
Magnitude2.8

Reviewed by USGSAlaska5y ago

M2.8 earthquake 148 km SSE of Chignik, Alaska

Wednesday, September 15, 2021, 01:09:52 UTC · 55.174°N, 157.124°W

A magnitude 2.8 earthquake struck 148 km SSE of Chignik, Alaska on Wednesday, September 15, 2021, 01:09:52 UTC, at a depth of 26.3 km (shallow).

Magnitude
2.8
Minor · ml
Depth
26 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

89 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

26 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 4 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.6 on September 16, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M4M51h6h1d3d7d14d30dMainshock M2.8
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 2.8152 km SE of Chignik, Alaska5y ago · 26 km NE of this epicenter
  2. 2.7144 km SE of Perryville, Alaska5y ago · 33 km SW of this epicenter
  3. 2.9144 km SE of Chignik, Alaska5y ago · 11 km NE of this epicenter
  4. 5.6181 km SE of Chignik, Alaska5y ago · 41 km E of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 342 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 · 67 km W of this epicenter
  2. 8.22021 Chignik, Alaska EarthquakeJuly 29, 2021 · 53 km NW of this epicenter
  3. 7.82020 Perryville, Alaska EarthquakeJuly 22, 2020 · 94 km W of this epicenter
  4. 7.62020 Sand Point, Alaska EarthquakeOctober 19, 2020 · 172 km W of this epicenter
  5. 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 177 km W of this epicenter
  6. 7.190 km SE of King Cove, AlaskaMay 14, 1948 · 266 km W of this epicenter
  7. 7.0113 km ESE of Chignik, AlaskaMay 4, 1923 · 77 km N of this epicenter
  8. 7.071 km SE of King Cove, AlaskaMay 30, 1991 · 295 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. The most severe:

  1. 2020M7.8

    Alaska

    22 Jul 2020 · 94 km away · intensity VII

    Limited damage (under $1M)tsunami

  2. 1938M8.2

    Alaska

    10 Nov 1938 · 86 km away · intensity VI

    tsunami

  3. 2021M8.2

    Alaska Peninsula

    29 Jul 2021 · 48 km away · intensity VIII

    tsunami

  4. 1788M8.0

    Alaska Peninsula

    6 Aug 1788 · 247 km away

    tsunami

  5. 1906M7.6

    Aleutian Islands

    23 Dec 1906 · 274 km away

  6. 2020M7.6

    Alaska

    19 Oct 2020 · 172 km away · intensity IX

    tsunami

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

Nearby trackers

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