M4.0 earthquake 80 km W of Adak, Alaska

A magnitude 4.0 earthquake struck 80 km W of Adak, Alaska on Thu, Jan 23, 2020, 5:30 PM HAST (03:30 UTC), 10 km (6 mi) below the surface.

A larger quake followed: M5.0 71 km WNW 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
4.0	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.163 · 10 stations
3.3	ML, local (Richter)	Alaska Earthquake Center	Preliminary

No one has reported feeling this quake to the USGS.

Reviewed by a seismologist.

Within 100 km, magnitude 1.5 and up: at least 201 in the 60 days after this one and at least 200 in the 30 days before it.

The first 60 of at least 201.

From the USGS Earthquake Hazards Program and its partner networks, event us60007piz (also filed as ak02013qv61c). Read Thu, Oct 1, 2026, 9:12 AM UTC.