Alaska earthquakes

M4.0 earthquake Alaska Peninsula

A magnitude 4.0 earthquake struck in the Alaska Peninsula on Tue, Aug 15, 2023, 10:09 AM AKDT (18:09 UTC), 35 km (22 mi) below the surface.

A larger quake followed: M5.4 47 km S of Sand Point, Alaska. This one was a foreshock.

Sand Point forecast More in Alaska

Map

Where this earthquake was located, with the others nearby. Select one for its page.

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The earthquake

Magnitude: 4.0 (mb, body-wave), light
Magnitude from: USGS National Earthquake Information Center
Local time: Tue, Aug 15, 2023, 10:09 AM AKDT
UTC: 2023-08-15 18:09:36 UTC
Depth: 35.0 km (21.7 mi), shallow
Epicenter: 54.778° N, 161.210° W
Region: Alaska
Felt reports: 1
Strongest shaking: I, not felt shaking
Tsunami flag: No
Status: Reviewed by a seismologist

Magnitude estimates

Different scales measure different things and differ by a few tenths. The USGS marks one as preferred, and it is the one this page uses.

Mag.	Scale	Computed by	Notes
4.0	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.184 · 9 stations
3.6	ML, local (Richter)	Alaska Earthquake Center	Preliminary

Shaking

The USGS ShakeMap: shaking estimated from seismic stations and the quake’s size, on the Modified Mercalli intensity scale.

Strongest estimated: I, not felt shaking
Peak ground acceleration: 0.0% of gravity
Peak ground velocity: -4.1 cm/s
Map: Automatic

USGS ShakeMap: estimated shaking intensity around the epicenter — Estimated shaking intensity. Map: USGS ShakeMap.

Did you feel it?

1 person reported to the USGS what they felt; the strongest reported shaking was III, weak shaking.

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 2.5 km horizontally, 2.0 km in depth
Magnitude uncertainty: ±0.18
Depth from: Operator assigned
Station coverage gap: 196°, poorly surrounded by stations
Stations used: 82

Nearest places

Distance and direction from each place to the epicenter, with its forecast.

Sand Point, AlaskaPopulation 1,064. Forecast77 kmSW

Nearby

Within 100 km, magnitude 1.5 and up: at least 199 in the 60 days after this one and at least 200 in the 30 days before it.

After

The first 60 of at least 199.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us7000knip (also filed as ak023afprl1f, ak023afprl5r). Read Mon, Oct 5, 2026, 6:59 AM UTC.