M3.3 Earthquake 89 km SE of Ugashik, Alaska — October 9, 2021
2021-10-09 20:23:32 UTC (2021-10-09) · approx. 10:23 AM UTC-10 local
On October 9, 2021 at 20:23 UTC, a magnitude 3.3 shallow crustal earthquake struck 89 km SE of Ugashik, Alaska, at a depth of 11.5 km and coordinates 57.0144°, -156.2295°.
Physical scale: An earthquake of magnitude 3.3 releases seismic energy equivalent to roughly 1.3 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 114 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
-156.2295°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 3.3 earthquake near Ugashik, Alaska?
The magnitude 3.3 earthquake that struck 89 km SE of Ugashik, Alaska on October 9, 2021 at 20:23 UTC had a depth of 11.5 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 3.3 earthquakes can continue for several days and gradually diminish over time.
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Understanding This Data
Magnitude 3.3 earthquakes are typically only recorded by instruments.
Authoritative source: USGS event page (event ID: ak021cyplk61). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, October 9, 2021). M3.3 Earthquake 89 km SE of Ugashik, Alaska — October 9, 2021. Retrieved December 18, 2021 from https://www.earthquaketracker.org/earthquakes/event/ak021cyplk61/