M5.9 Earthquake 87 km SSE of Adak, Alaska — March 21, 2025
2025-03-21 14:58:28 UTC (2025-03-21) · approx. 2:58 AM UTC-12 local
On March 21, 2025 at 14:58 UTC, a magnitude 5.9 shallow crustal earthquake struck 87 km SSE of Adak, Alaska, at a depth of 26.7 km and coordinates 51.1563°, -176.1097°. The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. This earthquake was detected by 222 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 536, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 5.9 releases seismic energy equivalent to roughly 11 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 7.1 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
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 | 3 |
| MMI 4 | light | 451 |
Earthquake Details
-176.1097°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 5.9 earthquake near Adak, Alaska?
The magnitude 5.9 earthquake that struck 87 km SSE of Adak, Alaska on March 21, 2025 at 14:58 UTC had a depth of 26.7 km. For context, this was a moderate earthquake that could be widely felt.
Where did the earthquake occur?
The earthquake epicenter was located at 51.1563°, -176.1097°, which is 87 km SSE of Adak, Alaska. View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.9 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 5.9 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: us7000pllx). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, March 21, 2025). M5.9 Earthquake 87 km SSE of Adak, Alaska — March 21, 2025. Retrieved May 29, 2025 from https://www.earthquaketracker.org/earthquakes/event/us7000pllx/