M4.2 Earthquake in the Unimak Island region, Alaska — August 12, 2023
2023-08-12 18:49:46 UTC (2023-08-12) · approx. 7:49 AM UTC-11 local
On August 12, 2023 at 18:49 UTC, a magnitude 4.2 shallow crustal earthquake struck in the Unimak Island region, Alaska, at a depth of 20.7 km and coordinates 53.3922°, -163.7453°.
Physical scale: An earthquake of magnitude 4.2 releases seismic energy equivalent to roughly 30 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 476 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
-163.7453°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.2 earthquake in the Unimak Island region, Alaska?
The magnitude 4.2 earthquake that struck in the Unimak Island region, Alaska on August 12, 2023 at 18:49 UTC had a depth of 20.7 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 4.2 earthquakes can continue for several days and gradually diminish over time.
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Understanding This Data
Magnitude 4.2 earthquakes are often felt but rarely cause damage.
Authoritative source: USGS event page (event ID: us6000kzlb). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, August 12, 2023). M4.2 Earthquake in the Unimak Island region, Alaska — August 12, 2023. Retrieved October 17, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000kzlb/