M4.0 earthquake 216 km W of Adak, Alaska

A magnitude 4.0 earthquake struck 216 km W of Adak, Alaska on Sat, Dec 28, 2019, 5:31 AM HAST (15:31 UTC), 98 km (61 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
4.0	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.368 · 2 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: at least 199 in the 60 days after this one and 22 in the 30 days before it.

The first 60 of at least 199.

From the USGS Earthquake Hazards Program and its partner networks, event us70006s18 (also filed as ak019gmxnu5k). Read Thu, Oct 1, 2026, 7:04 PM UTC.