M4.2 earthquake 125 km SW of Adak, Alaska

A magnitude 4.2 earthquake struck 125 km SW of Adak, Alaska on Mon, Jan 20, 2020, 12:07 PM HAST (22:07 UTC), 35 km (22 mi) below the surface.

A larger quake followed: M6.2 84 km W 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
4.2	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.058 · 82 stations
4.1	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 70 in the 30 days before it.

The first 60 of at least 201.

From the USGS Earthquake Hazards Program and its partner networks, event us60007bn9 (also filed as ak020xfw3dc). Read Thu, Oct 1, 2026, 4:20 AM UTC.