M4.9 earthquake 71 km SSW of Adak, Alaska

A magnitude 4.9 earthquake struck 71 km SSW of Adak, Alaska on Mon, Oct 20, 2025, 9:45 AM HADT (18:45 UTC), 37 km (23 mi) below the surface.

A larger quake followed: M5.5 67 km SSW 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
4.9	Mwr, regional moment	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.098 · 10 stations
4.8	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.

2 people reported to the USGS what they felt; the strongest reported shaking was III, weak shaking.

How the rock slipped, from the moment tensor, and the USGS estimate of landslides and liquefaction.

Reviewed by a seismologist.

Within 100 km, magnitude 1.9 and up: 104 in the 60 days after this one and 11 in the 30 days before it.

The first 60 of 104.

From the USGS Earthquake Hazards Program and its partner networks, event us6000ric9 (also filed as ak025dgvg6v5). Read Fri, Oct 2, 2026, 9:53 AM UTC.