M5.5 Earthquake 260 km W of Adak, Alaska — February 28, 2024
2024-02-28 15:50:21 UTC (2024-02-28) · approx. 3:50 AM UTC+12 local
On February 28, 2024 at 15:50 UTC, a magnitude 5.5 intermediate depth earthquake struck 260 km W of Adak, Alaska, at a depth of 120.0 km and coordinates 52.0016°, 179.5832°. The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. This earthquake was detected by 144 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 465, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 5.5 releases seismic energy equivalent to roughly 3 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 3.8 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
179.5832°E
Technical Information
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Common Questions
How strong was the magnitude 5.5 earthquake near Adak, Alaska?
The magnitude 5.5 earthquake that struck 260 km W of Adak, Alaska on February 28, 2024 at 15:50 UTC had a depth of 120.0 km. For context, this was a moderate earthquake that could be widely felt.
Where did the earthquake occur?
The earthquake epicenter was located at 52.0016°, 179.5832°, which is 260 km W of Adak, Alaska. View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.5 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 5.5 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: us6000mflq). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2024, February 28, 2024). M5.5 Earthquake 260 km W of Adak, Alaska — February 28, 2024. Retrieved February 13, 2026 from https://www.earthquaketracker.org/earthquakes/event/us6000mflq/