M3.8 Earthquake 285 km WSW of Adak, Alaska — December 4, 2021
2021-12-04 17:58:16 UTC (2021-12-04) · approx. 5:58 AM UTC+12 local
On December 4, 2021 at 17:58 UTC, a magnitude 3.8 shallow crustal earthquake struck 285 km WSW of Adak, Alaska, at a depth of 28.8 km and coordinates 50.9333°, 179.5440°.
Physical scale: An earthquake of magnitude 3.8 releases seismic energy equivalent to roughly 7.6 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 252 m — a useful intuition for the size of the slip patch on the fault.
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
179.5440°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 3.8 earthquake near Adak, Alaska?
The magnitude 3.8 earthquake that struck 285 km WSW of Adak, Alaska on December 4, 2021 at 17:58 UTC had a depth of 28.8 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 3.8 earthquakes can continue for several days and gradually diminish over time.
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Understanding This Data
Magnitude 3.8 earthquakes are typically only recorded by instruments.
Authoritative source: USGS event page (event ID: us6000g92j). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, December 4, 2021). M3.8 Earthquake 285 km WSW of Adak, Alaska — December 4, 2021. Retrieved February 12, 2022 from https://www.earthquaketracker.org/earthquakes/event/us6000g92j/