M3.9 Earthquake 48 km ESE of Nikolski, Alaska — October 27, 2021
2021-10-27 22:31:48 UTC (2021-10-27) · approx. 11:31 AM UTC-11 local
On October 27, 2021 at 22:31 UTC, a magnitude 3.9 shallow crustal earthquake struck 48 km ESE of Nikolski, Alaska, at a depth of 41.8 km and coordinates 52.8021°, -168.1854°.
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.
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
-168.1854°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 3.9 earthquake near Nikolski, Alaska?
The magnitude 3.9 earthquake that struck 48 km ESE of Nikolski, Alaska on October 27, 2021 at 22:31 UTC had a depth of 41.8 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 3.9 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: us7000fpal). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, October 27, 2021). M3.9 Earthquake 48 km ESE of Nikolski, Alaska — October 27, 2021. Retrieved January 8, 2022 from https://www.earthquaketracker.org/earthquakes/event/us7000fpal/