M3.9 earthquake 83 km SW of Atka, Alaska

A magnitude 3.9 earthquake struck 83 km SW of Atka, Alaska on Sun, Sep 28, 2025, 4:38 AM HADT (13:38 UTC), 35 km (22 mi) below the surface.

A larger quake followed: M4.9 47 km SE of Adak, Alaska. This one was a foreshock.

Map

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

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
3.9	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.143 · 13 stations
3.6	ML, local (Richter)	Alaska Earthquake Center	Preliminary

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

No one has reported feeling this quake to the USGS.

Reviewed by a seismologist.

Within 100 km, magnitude 1.5 and up: 32 in the 60 days after this one and 27 in the 30 days before it.

From the USGS Earthquake Hazards Program and its partner networks, event us6000rdgj (also filed as ak025cgem1sn). Read Fri, Oct 2, 2026, 4:06 PM UTC.