M4.5 Earthquake 185 km SW of Nikolski, Alaska — September 13, 2025
2025-09-13 22:29:55 UTC (2025-09-13) · approx. 11:29 AM UTC-11 local
On September 13, 2025 at 22:29 UTC, a magnitude 4.5 shallow crustal earthquake struck 185 km SW of Nikolski, Alaska, at a depth of 18.8 km and coordinates 51.6940°, -170.6741°. This earthquake was detected by 90 seismic stations with good location accuracy and was assigned a USGS significance rating of 312, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 4.5 releases seismic energy equivalent to roughly 85 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 767 m — a useful intuition for the size of the slip patch on the fault.
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
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
-170.6741°E
Technical Information
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Common Questions
How strong was the magnitude 4.5 earthquake near Nikolski, Alaska?
The magnitude 4.5 earthquake that struck 185 km SW of Nikolski, Alaska on September 13, 2025 at 22:29 UTC had a depth of 18.8 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 51.6940°, -170.6741°, which is 185 km SW of Nikolski, Alaska. View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.5 earthquakes can continue for several days and gradually diminish over time.
Has Alaska had earthquakes this big before?
The largest recorded earthquake in Alaska was the M9.2 Great Alaska earthquake of March 27, 1964. Today's magnitude 4.5 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: us7000qw1s). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, September 13, 2025). M4.5 Earthquake 185 km SW of Nikolski, Alaska — September 13, 2025. Retrieved December 3, 2025 from https://www.earthquaketracker.org/earthquakes/event/us7000qw1s/