M3.8 Earthquake 253 km ESE of Attu Station, Alaska — February 21, 2023
2023-02-21 19:43:06 UTC (2023-02-21) · approx. 7:43 AM UTC+12 local
On February 21, 2023 at 19:43 UTC, a magnitude 3.8 intermediate depth earthquake struck 253 km ESE of Attu Station, Alaska, at a depth of 124.5 km and coordinates 52.2274°, 176.7862°.
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.
This earthquake is part of an ongoing aftershock sequence following the magnitude 5.0 mainshock that occurred 9 days ago 231 km ESE of Attu Station, Alaska. Since the mainshock, the USGS has recorded 42 aftershocks in this area. Aftershock activity is expected to continue for days to weeks as stresses on surrounding faults redistribute.
Earthquake Details
176.7862°E
Technical Information
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Common Questions
How strong was the magnitude 3.8 earthquake near Attu Station, Alaska?
The magnitude 3.8 earthquake that struck 253 km ESE of Attu Station, Alaska on February 21, 2023 at 19:43 UTC had a depth of 124.5 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 3.8 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M5.0 one earlier?
No. This magnitude 3.8 earthquake is an aftershock of the larger magnitude 5.0 mainshock that occurred earlier 231 km ESE of Attu Station, Alaska. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
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Understanding This Data
Magnitude 3.8 earthquakes are typically only recorded by instruments.
Authoritative source: USGS event page (event ID: us7000jgj0). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, February 21, 2023). M3.8 Earthquake 253 km ESE of Attu Station, Alaska — February 21, 2023. Retrieved April 29, 2023 from https://www.earthquaketracker.org/earthquakes/event/us7000jgj0/