M4.1 Earthquake 173 km W of Nikolski, Alaska — September 17, 2026
2026-09-17 14:39:42 UTC (1 day ago) · approx. 3:39 AM UTC-11 local
On September 17, 2026 at 14:39 UTC, a magnitude 4.1 intermediate depth earthquake struck 173 km W of Nikolski, Alaska, at a depth of 97.2 km and coordinates 52.8259°, -171.4285°.
Physical scale: An earthquake of magnitude 4.1 releases seismic energy equivalent to roughly 21 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 406 m — 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 6.5 mainshock that occurred 1 day ago 169 km W of Nikolski, Alaska. Since the mainshock, the USGS has recorded 3 aftershocks in this area. Aftershock activity is expected to continue for weeks to months as stresses on surrounding faults redistribute.
ShakeMap — predicted shaking intensity
Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.
Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS
Earthquake Details
-171.4285°E
Technical Information
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Common Questions
How strong was the magnitude 4.1 earthquake near Nikolski, Alaska?
The magnitude 4.1 earthquake that struck 173 km W of Nikolski, Alaska on September 17, 2026 at 14:39 UTC had a depth of 97.2 km. For context, this was a light earthquake commonly felt near the epicenter.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.1 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M6.5 one earlier?
No. This magnitude 4.1 earthquake is an aftershock of the larger magnitude 6.5 mainshock that occurred earlier 169 km W of Nikolski, Alaska. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
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Understanding This Data
Magnitude 4.1 earthquakes are often felt but rarely cause damage.
Authoritative source: USGS event page (event ID: us7000ti2f). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2026, September 17, 2026). M4.1 Earthquake 173 km W of Nikolski, Alaska — September 17, 2026. Retrieved September 18, 2026 from https://www.earthquaketracker.org/earthquakes/event/us7000ti2f/