M4.1 earthquake 171 km S of Nikolski, Alaska

A magnitude 4.1 earthquake struck 171 km S of Nikolski, Alaska on Thu, Jul 30, 2020, 11:45 PM AKDT (07:45 UTC), 10 km (6 mi) below the surface.

A larger quake followed: M5.5 129 km SSW of Nikolski, 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
4.1	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.099 · 28 stations
3.6	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: 36 in the 60 days after this one and 6 in the 30 days before it.

From the USGS Earthquake Hazards Program and its partner networks, event us6000b7bt (also filed as ak0209sdwoct). Read Sat, Oct 3, 2026, 3:35 PM UTC.