M4.3 Earthquake 145 km S of False Pass, Alaska — February 25, 2023
2023-02-25 19:56:37 UTC (2023-02-25) · approx. 8:56 AM UTC-11 local
On February 25, 2023 at 19:56 UTC, a magnitude 4.3 shallow crustal earthquake struck 145 km S of False Pass, Alaska, at a depth of 29.5 km and coordinates 53.5521°, -163.2140°.
Physical scale: An earthquake of magnitude 4.3 releases seismic energy equivalent to roughly 43 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 558 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 16 days ago 143 km S of False Pass, Alaska. Since the mainshock, the USGS has recorded 28 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
-163.2140°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.3 earthquake near False Pass, Alaska?
The magnitude 4.3 earthquake that struck 145 km S of False Pass, Alaska on February 25, 2023 at 19:56 UTC had a depth of 29.5 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 4.3 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 4.3 earthquake is an aftershock of the larger magnitude 5.0 mainshock that occurred earlier 143 km S of False Pass, Alaska. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
Actions
Understanding This Data
Magnitude 4.3 earthquakes are often felt but rarely cause damage.
Authoritative source: USGS event page (event ID: us6000jrmy). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, February 25, 2023). M4.3 Earthquake 145 km S of False Pass, Alaska — February 25, 2023. Retrieved April 29, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000jrmy/