M4.0 Earthquake near Rat Islands, Aleutian Islands, Alaska — October 21, 2021
2021-10-21 18:01:20 UTC (2021-10-21) · approx. 6:01 AM UTC+12 local
On October 21, 2021 at 18:01 UTC, a magnitude 4.0 intermediate depth earthquake struck near Rat Islands, Aleutian Islands, Alaska, at a depth of 97.1 km and coordinates 51.8097°, 178.4293°.
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
178.4293°E
Technical Information
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Common Questions
How strong was the magnitude 4.0 earthquake near Rat Islands, Aleutian Islands, Alaska?
The magnitude 4.0 earthquake that struck near Rat Islands, Aleutian Islands, Alaska on October 21, 2021 at 18:01 UTC had a depth of 97.1 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: us7000fp8e). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, October 21, 2021). M4.0 Earthquake near Rat Islands, Aleutian Islands, Alaska — October 21, 2021. Retrieved December 25, 2021 from https://www.earthquaketracker.org/earthquakes/event/us7000fp8e/