M2.7 earthquake 48 km S of False Pass, Alaska

Tuesday, September 12, 2023, 01:47:57 UTC · 54.420°N, 163.295°W

A magnitude 2.7 earthquake struck 48 km S of False Pass, Alaska on Tuesday, September 12, 2023, 01:47:57 UTC, at a depth of 78.8 km (intermediate).

Magnitude: 2.7; Minor · ml
Depth: 79 km; Intermediate
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

169 kg of TNT

That is about 1/88,990 of the Hiroshima bomb. A magnitude 5.0 releases about 2,818 times more energy.

Tectonic setting

129 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: intermediate

79 km

Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.

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 6 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M3.4 on October 10, 2023. 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 419 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 9 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 169 recorded deaths. The most severe:

1946M8.6
Unimak Island
1 Apr 1946 · 108 km away · intensity VI
168 deaths$26 million damagetsunami
2023M7.2
Alaska Peninsula
16 Jul 2023 · 164 km away · intensity VI
1 deathtsunami
1788M8.0
Alaska Peninsula
6 Aug 1788 · 161 km away
tsunami
2020M7.6
Alaska
19 Oct 2020 · 238 km away · intensity IX
tsunami
1948M7.5
Alaska Peninsula
14 May 1948 · 149 km away
1957M7.5
Aleutian Islands: Fox Islands
22 Mar 1957 · 138 km away · intensity V

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

Nearby trackers