M5.0 Earthquake 63 km SSW of Nikolski, Alaska — September 3, 2026

On September 3, 2026 at 20:22 UTC, a magnitude 5.0 shallow crustal earthquake struck 63 km SSW of Nikolski, Alaska, at a depth of 33.2 km and coordinates 52.4375°, -169.3032°. This earthquake was detected by 60 seismic stations with good location accuracy and was assigned a USGS significance rating of 385, placing it among routine seismic activity.

Physical scale: An earthquake of magnitude 5.0 releases seismic energy equivalent to roughly 477 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 1.7 km — a useful intuition for the size of the slip patch on the fault.

This earthquake is part of an ongoing aftershock sequence following the magnitude 5.4 mainshock that occurred 11 days ago 105 km SSW of Nikolski, Alaska. Since the mainshock, the USGS has recorded 158 aftershocks in this area. Aftershock activity is expected to continue for days to weeks as stresses on surrounding faults redistribute.

The epicenter is located in Alaska, a region characterized by Pacific Plate subduction beneath the North American Plate, producing frequent megathrust and crustal earthquakes along the Aleutian arc. The nearest mapped fault system is the Aleutian megathrust. View all earthquakes in Alaska.

Learn more: Magnitude scale · Aftershock sequences