M4.0 earthquake 186 km SSE of Adak, Alaska

A magnitude 4.0 earthquake struck 186 km SSE of Adak, Alaska on Tue, Dec 8, 2020, 7:32 PM HAST (05:32 UTC), 10 km (6 mi) below the surface.

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 · ±0.072 · 52 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: 7 in the 60 days after this one and 4 in the 30 days before it.

From the USGS Earthquake Hazards Program and its partner networks, event us7000cpji (also filed as ak020ft01hej). Read Fri, Oct 2, 2026, 9:33 AM UTC.