M5.6 Earthquake 133 km SE of Old Harbor, Alaska — September 1, 2025
2025-09-01 11:02:09 UTC (2025-09-01) · approx. 1:02 AM UTC-10 local
On September 1, 2025 at 11:02 UTC, a magnitude 5.6 shallow crustal earthquake struck 133 km SE of Old Harbor, Alaska, at a depth of 12.0 km and coordinates 56.2482°, -151.9738°. The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. The nearest populated place is Kodiak Station (population 1,301).
Physical scale: An earthquake of magnitude 5.6 releases seismic energy equivalent to roughly 4 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 4.4 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
Nearest Populated Places
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
Population exposure (USGS PAGER)
Estimated population that experienced each level of shaking. Based on the USGS PAGER rapid impact assessment, which combines ShakeMap output with global population grids.
| Shaking intensity (MMI) | Description | Population exposed |
|---|---|---|
| MMI 3 | weak | 12,458 |
Earthquake Details
-151.9738°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 5.6 earthquake near Old Harbor, Alaska?
The magnitude 5.6 earthquake that struck 133 km SE of Old Harbor, Alaska on September 1, 2025 at 11:02 UTC had a depth of 12.0 km. For context, this was a moderate earthquake that could be widely felt.
Where did the earthquake occur?
The earthquake epicenter was located at 56.2482°, -151.9738°, which is 133 km SE of Old Harbor, Alaska. The nearest populated place is Kodiak Station (population 1,301). View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.6 earthquakes can continue for days to weeks 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 5.6 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: ak025b7povrc). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, September 1, 2025). M5.6 Earthquake 133 km SE of Old Harbor, Alaska — September 1, 2025. Retrieved July 20, 2026 from https://www.earthquaketracker.org/earthquakes/event/ak025b7povrc/