M4.0 earthquake 132 km SE of Perryville, Alaska

A magnitude 4.0 earthquake struck 132 km SE of Perryville, Alaska on Fri, Jul 30, 2021, 1:58 AM AKDT (09:58 UTC), 47 km (29 mi) below the surface.

A larger quake followed: M6.9 125 km SE of Perryville, 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	ML, local (Richter)	Alaska Earthquake Center	Preferred · Preliminary
4.4	mb, body-wave	USGS National Earthquake Information Center	Reviewed · ±0.093 · 35 stations

The USGS ShakeMap: shaking estimated from seismic stations and the quake’s size, on the Modified Mercalli intensity scale.

1 person reported to the USGS what they felt; the strongest reported shaking was II, weak shaking.

The USGS PAGER system estimates deaths and economic losses from the shaking and the population and buildings exposed to it.

Reviewed by a seismologist.

Distance and direction from each place to the epicenter, with its forecast.

Within 100 km, magnitude 1.5 and up: at least 202 in the 60 days after this one and at least 200 in the 30 days before it.

The first 60 of at least 202.

From the USGS Earthquake Hazards Program and its partner networks, event ak0219p43m23 (also filed as us6000f0kf). Read Fri, Oct 2, 2026, 7:53 AM UTC.