M4.8 Earthquake 163 km S of Attu Station, Alaska — May 20, 2023
2023-05-20 19:00:06 UTC (2023-05-20) · approx. 7:00 AM UTC+12 local
On May 20, 2023 at 19:00 UTC, a magnitude 4.8 shallow crustal earthquake struck 163 km S of Attu Station, Alaska, at a depth of 10.0 km and coordinates 51.3954°, 172.8412°. This earthquake was detected by 59 seismic stations with good location accuracy and was assigned a USGS significance rating of 354, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 4.8 releases seismic energy equivalent to roughly 239 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 1.2 km — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in Alaska, a region characterized by Pacific Plate subduction beneath the North American Plate, producing frequent megathrust and crustal earthquakes along the Aleutian arc. The nearest mapped fault system is the Aleutian megathrust. View all earthquakes in Alaska.
Learn more: Magnitude scale · Aftershock sequences
Earthquake Details
172.8412°E
Technical Information
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Common Questions
How strong was the magnitude 4.8 earthquake near Attu Station, Alaska?
The magnitude 4.8 earthquake that struck 163 km S of Attu Station, Alaska on May 20, 2023 at 19:00 UTC had a depth of 10.0 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 51.3954°, 172.8412°, which is 163 km S of Attu Station, Alaska. View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.8 earthquakes can continue for several days and gradually diminish over time.
Has Alaska had earthquakes this big before?
The largest recorded earthquake in Alaska was the M9.2 Great Alaska earthquake of March 27, 1964. Today's magnitude 4.8 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: us6000kdhf). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, May 20, 2023). M4.8 Earthquake 163 km S of Attu Station, Alaska — May 20, 2023. Retrieved July 24, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000kdhf/