M3.9 Earthquake 149 km S of False Pass, Alaska — April 22, 2021
2021-04-22 23:25:05 UTC (2021-04-22) · approx. 12:25 PM UTC-11 local
On April 22, 2021 at 23:25 UTC, a magnitude 3.9 shallow crustal earthquake struck 149 km S of False Pass, Alaska, at a depth of 18.0 km and coordinates 53.5102°, -163.4178°.
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.
Earthquake Details
-163.4178°E
Technical Information
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Common Questions
How strong was the magnitude 3.9 earthquake near False Pass, Alaska?
The magnitude 3.9 earthquake that struck 149 km S of False Pass, Alaska on April 22, 2021 at 23:25 UTC had a depth of 18.0 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.
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Understanding This Data
Magnitude 3.9 earthquakes are typically only recorded by instruments.
Authoritative source: USGS event page (event ID: us6000e3t8). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, April 22, 2021). M3.9 Earthquake 149 km S of False Pass, Alaska — April 22, 2021. Retrieved July 3, 2021 from https://www.earthquaketracker.org/earthquakes/event/us6000e3t8/