M4.3 earthquake 162 km SE of Chignik, Alaska

Saturday, December 25, 2021, 10:15:55 UTC · 55.150°N, 156.799°W

A magnitude 4.3 earthquake struck 162 km SE of Chignik, Alaska on Saturday, December 25, 2021, 10:15:55 UTC, at a depth of 2.4 km (shallow).

Magnitude: 4.3; Light · ml
Depth: 2 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: II; Weak (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

43 tons of TNT

That is about 1/354 of the Hiroshima bomb. A magnitude 5.0 releases about 11 times more energy.

Tectonic setting

79 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

2 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 5 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M3.2 on January 5, 2022. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 349 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

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:

1900M8.3
Kodiak Island
9 Oct 1900 · 298 km away · intensity VIII
Limited damage (under $1M)
2020M7.8
Alaska
22 Jul 2020 · 115 km away · intensity VII
Limited damage (under $1M)tsunami
1938M8.2
Alaska
10 Nov 1938 · 106 km away · intensity VI
tsunami
2021M8.2
Alaska Peninsula
29 Jul 2021 · 69 km away · intensity VIII
tsunami
1788M8.0
Alaska Peninsula
6 Aug 1788 · 268 km away
tsunami
1906M7.6
Aleutian Islands
23 Dec 1906 · 261 km away

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

Nearby trackers