M4.0 Earthquake 102 km SSE of Adak, Alaska — March 20, 2025
2025-03-20 20:27:33 UTC (2025-03-20) · approx. 8:27 AM UTC-12 local
On March 20, 2025 at 20:27 UTC, a magnitude 4.0 shallow crustal earthquake struck 102 km SSE of Adak, Alaska, at a depth of 10.0 km and coordinates 51.0239°, -176.0609°.
Physical scale: An earthquake of magnitude 4.0 releases seismic energy equivalent to roughly 15 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 347 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 5.0 mainshock that occurred 5 days ago 94 km SSE of Adak, Alaska. Since the mainshock, the USGS has recorded 5 aftershocks in this area. Aftershock activity is expected to continue for days to weeks as stresses on surrounding faults redistribute.
Earthquake Details
-176.0609°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.0 earthquake near Adak, Alaska?
The magnitude 4.0 earthquake that struck 102 km SSE of Adak, Alaska on March 20, 2025 at 20:27 UTC had a depth of 10.0 km. For context, this was a light earthquake commonly felt near the epicenter.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.0 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M5.0 one earlier?
No. This magnitude 4.0 earthquake is an aftershock of the larger magnitude 5.0 mainshock that occurred earlier 94 km SSE of Adak, Alaska. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
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Understanding This Data
Magnitude 4.0 earthquakes are often felt but rarely cause damage.
Authoritative source: USGS event page (event ID: us7000pll5). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, March 20, 2025). M4.0 Earthquake 102 km SSE of Adak, Alaska — March 20, 2025. Retrieved May 29, 2025 from https://www.earthquaketracker.org/earthquakes/event/us7000pll5/