M4.0 Earthquake 78 km SW of Nikolski, Alaska — January 29, 2023
2023-01-29 22:36:39 UTC (2023-01-29) · approx. 11:36 AM UTC-11 local
On January 29, 2023 at 22:36 UTC, a magnitude 4.0 shallow crustal earthquake struck 78 km SW of Nikolski, Alaska, at a depth of 57.1 km and coordinates 52.4676°, -169.7176°.
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.
This earthquake is part of an ongoing aftershock sequence following the magnitude 5.2 mainshock that occurred 3 hours ago 97 km SSW of Nikolski, Alaska. Since the mainshock, the USGS has recorded 59 aftershocks in this area. Aftershock activity is expected to continue for days to weeks as stresses on surrounding faults redistribute.
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
-169.7176°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.0 earthquake near Nikolski, Alaska?
The magnitude 4.0 earthquake that struck 78 km SW of Nikolski, Alaska on January 29, 2023 at 22:36 UTC had a depth of 57.1 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.
Is this the same earthquake as the M5.2 one earlier?
No. This magnitude 4.0 earthquake is an aftershock of the larger magnitude 5.2 mainshock that occurred earlier 97 km SSW of Nikolski, Alaska. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
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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: us6000jk84). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, January 29, 2023). M4.0 Earthquake 78 km SW of Nikolski, Alaska — January 29, 2023. Retrieved April 13, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000jk84/