M4.2 earthquake 238 km WSW of Adak, Alaska

A magnitude 4.2 earthquake struck 238 km WSW of Adak, Alaska on Wed, Jan 22, 2020, 1:09 AM GMT-12 (13:09 UTC), 35 km (22 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 · ±0.092 · 33 stations
4.0	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 199 in the 60 days after this one and 46 in the 30 days before it.

The first 60 of at least 199.

From the USGS Earthquake Hazards Program and its partner networks, event us60007ctp (also filed as ak02010lm7rf). Read Thu, Oct 1, 2026, 8:02 AM UTC.