M4.2 earthquake 250 km WSW of Adak, Alaska

A magnitude 4.2 earthquake struck 250 km WSW of Adak, Alaska on Wed, Jan 22, 2020, 4:35 AM GMT-12 (16:35 UTC), 10 km (6 mi) below the surface.

A larger quake followed: M6.1 240 km WSW 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 · ±0.045 · 138 stations
3.9	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: 189 in the 60 days after this one and 34 in the 30 days before it.

The first 60 of 189.

From the USGS Earthquake Hazards Program and its partner networks, event us60007cxd (also filed as ak02010nk6ts). Read Thu, Oct 1, 2026, 2:33 AM UTC.