M4.0 Earthquake 29 km SSW of Adak, Alaska — December 16, 2021
2021-12-16 19:48:27 UTC (2021-12-16) · approx. 7:48 AM UTC-12 local
On December 16, 2021 at 19:48 UTC, a magnitude 4.0 intermediate depth earthquake struck 29 km SSW of Adak, Alaska, at a depth of 70.5 km and coordinates 51.6330°, -176.8276°.
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.
Earthquake Details
-176.8276°E
Technical Information
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Common Questions
How strong was the magnitude 4.0 earthquake near Adak, Alaska?
The magnitude 4.0 earthquake that struck 29 km SSW of Adak, Alaska on December 16, 2021 at 19:48 UTC had a depth of 70.5 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.
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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: us6000gf3l). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, December 16, 2021). M4.0 Earthquake 29 km SSW of Adak, Alaska — December 16, 2021. Retrieved February 24, 2022 from https://www.earthquaketracker.org/earthquakes/event/us6000gf3l/