M4.1 Earthquake 221 km SE of Attu Station, Alaska — July 21, 2023
2023-07-21 22:05:51 UTC (2023-07-21) · approx. 10:05 AM UTC+12 local
On July 21, 2023 at 22:05 UTC, a magnitude 4.1 shallow crustal earthquake struck 221 km SE of Attu Station, Alaska, at a depth of 30.0 km and coordinates 51.5405°, 175.6392°.
Physical scale: An earthquake of magnitude 4.1 releases seismic energy equivalent to roughly 21 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 406 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
175.6392°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.1 earthquake near Attu Station, Alaska?
The magnitude 4.1 earthquake that struck 221 km SE of Attu Station, Alaska on July 21, 2023 at 22:05 UTC had a depth of 30.0 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 4.1 earthquakes can continue for several days and gradually diminish over time.
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Understanding This Data
Magnitude 4.1 earthquakes are often felt but rarely cause damage.
Authoritative source: USGS event page (event ID: us7000khi9). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, July 21, 2023). M4.1 Earthquake 221 km SE of Attu Station, Alaska — July 21, 2023. Retrieved September 28, 2023 from https://www.earthquaketracker.org/earthquakes/event/us7000khi9/