M4.9 Earthquake 128 km SE of Old Harbor, Alaska — September 1, 2025
2025-09-01 11:45:47 UTC (2025-09-01) · approx. 1:45 AM UTC-10 local
On September 1, 2025 at 11:45 UTC, a magnitude 4.9 shallow crustal earthquake struck 128 km SE of Old Harbor, Alaska, at a depth of 10.5 km and coordinates 56.2886°, -152.0314°.
Physical scale: An earthquake of magnitude 4.9 releases seismic energy equivalent to roughly 338 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 1.4 km — 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
-152.0314°E
Technical Information
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Common Questions
How strong was the magnitude 4.9 earthquake near Old Harbor, Alaska?
The magnitude 4.9 earthquake that struck 128 km SE of Old Harbor, Alaska on September 1, 2025 at 11:45 UTC had a depth of 10.5 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 56.2886°, -152.0314°, which is 128 km SE of Old Harbor, Alaska. View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.9 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 4.9 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: ak025b7py6gc). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, September 1, 2025). M4.9 Earthquake 128 km SE of Old Harbor, Alaska — September 1, 2025. Retrieved November 19, 2025 from https://www.earthquaketracker.org/earthquakes/event/ak025b7py6gc/