M3.9 Earthquake 232 km ESE of Attu Station, Alaska — April 29, 2026
2026-04-29 23:20:49 UTC (2026-04-29) · approx. 11:20 AM UTC+12 local
On April 29, 2026 at 23:20 UTC, a magnitude 3.9 shallow crustal earthquake struck 232 km ESE of Attu Station, Alaska, at a depth of 23.0 km and coordinates 52.1777°, 176.4369°.
Physical scale: An earthquake of magnitude 3.9 releases seismic energy equivalent to roughly 11 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 296 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 6 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.
Earthquake Details
176.4369°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 3.9 earthquake near Attu Station, Alaska?
The magnitude 3.9 earthquake that struck 232 km ESE of Attu Station, Alaska on April 29, 2026 at 23:20 UTC had a depth of 23.0 km. For context, this was a minor earthquake typically detected only by instruments.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 3.9 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 3.9 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.
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.
Actions
Understanding This Data
Magnitude 3.9 earthquakes are typically only recorded by instruments.
Authoritative source: USGS event page (event ID: us6000svz2). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2026, April 29, 2026). M3.9 Earthquake 232 km ESE of Attu Station, Alaska — April 29, 2026. Retrieved May 12, 2026 from https://www.earthquaketracker.org/earthquakes/event/us6000svz2/