M3.8 earthquake 92 km ESE of Adak, Alaska

A magnitude 3.8 earthquake struck 92 km ESE of Adak, Alaska on Thu, Sep 20, 2018, 5:06 AM HADT (14:06 UTC), 34 km (21 mi) below the surface.

A larger quake followed: M4.6 93 km S of Atka, 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
3.8	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.111 · 21 stations
3.4	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: 109 in the 60 days after this one and 93 in the 30 days before it.

The first 60 of 109.

From the USGS Earthquake Hazards Program and its partner networks, event us1000h3ag (also filed as ak018c36pqrx). Read Sat, Oct 3, 2026, 6:47 AM UTC.