M4.5 Earthquake 156 km WNW of Attu Station, Alaska — September 29, 2021
2021-09-29 23:29:19 UTC (2021-09-29) · approx. 10:29 AM UTC+11 local
On September 29, 2021 at 23:29 UTC, a magnitude 4.5 shallow crustal earthquake struck 156 km WNW of Attu Station, Alaska, at a depth of 30.3 km and coordinates 53.2868°, 170.9640°.
Physical scale: An earthquake of magnitude 4.5 releases seismic energy equivalent to roughly 85 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 767 m — 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
170.9640°E
Technical Information
Common Questions
How strong was the magnitude 4.5 earthquake near Attu Station, Alaska?
The magnitude 4.5 earthquake that struck 156 km WNW of Attu Station, Alaska on September 29, 2021 at 23:29 UTC had a depth of 30.3 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 53.2868°, 170.9640°, which is 156 km WNW of Attu Station, Alaska. View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.5 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 4.5 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: us6000fqa7). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, September 29, 2021). M4.5 Earthquake 156 km WNW of Attu Station, Alaska — September 29, 2021. Retrieved December 4, 2021 from https://www.earthquaketracker.org/earthquakes/event/us6000fqa7/