M4.5 Earthquake 247 km ESE of Attu Station, Alaska — March 4, 2026
2026-03-04 19:39:50 UTC (2026-03-04) · approx. 7:39 AM UTC+12 local
Aftershock of the M5.8 mainshock.
On March 4, 2026 at 19:39 UTC, a magnitude 4.5 shallow crustal earthquake struck 247 km ESE of Attu Station, Alaska, at a depth of 10.0 km and coordinates 51.9928°, 176.5410°. This earthquake was detected by 97 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.
This earthquake is part of an ongoing aftershock sequence following the magnitude 5.8 mainshock that occurred 7 days ago 235 km ESE of Attu Station, Alaska. Since the mainshock, the USGS has recorded 19 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
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
176.5410°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.5 earthquake near Attu Station, Alaska?
The magnitude 4.5 earthquake that struck 247 km ESE of Attu Station, Alaska on March 4, 2026 at 19:39 UTC had a depth of 10.0 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 51.9928°, 176.5410°, which is 247 km ESE of Attu Station, 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.
Is this the same earthquake as the M5.8 one earlier?
No. This magnitude 4.5 earthquake is an aftershock of the larger magnitude 5.8 mainshock that occurred earlier 235 km ESE of Attu Station, Alaska. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
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.
What should I do after an earthquake?
If you were in the affected area: check yourself and others for injuries, inspect your home for damage, and be prepared for aftershocks. For detailed guidance, see our earthquake safety guide and emergency planning resources.
Authoritative source: USGS event page (event ID: us7000s22b). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2026, March 4, 2026). M4.5 Earthquake 247 km ESE of Attu Station, Alaska — March 4, 2026. Retrieved May 13, 2026 from https://www.earthquaketracker.org/earthquakes/event/us7000s22b/