M3.9 Earthquake 72 km S of Nikolski, Alaska — June 13, 2021
2021-06-13 17:48:13 UTC (2021-06-13) · approx. 6:48 AM UTC-11 local
On June 13, 2021 at 17:48 UTC, a magnitude 3.9 shallow crustal earthquake struck 72 km S of Nikolski, Alaska, at a depth of 37.7 km and coordinates 52.3026°, -168.6623°.
Physical scale: An earthquake of magnitude 3.9 releases seismic energy equivalent to roughly 11 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 296 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 23 days ago 63 km SSW of Nikolski, Alaska. Since the mainshock, the USGS has recorded 23 aftershocks in this area. Aftershock activity is expected to continue for days to weeks as stresses on surrounding faults redistribute.
Earthquake Details
-168.6623°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 3.9 earthquake near Nikolski, Alaska?
The magnitude 3.9 earthquake that struck 72 km S of Nikolski, Alaska on June 13, 2021 at 17:48 UTC had a depth of 37.7 km. For context, this was a minor earthquake typically detected only by instruments.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 3.9 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 3.9 earthquake is an aftershock of the larger magnitude 5.0 mainshock that occurred earlier 63 km SSW of Nikolski, Alaska. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
Actions
Understanding This Data
Magnitude 3.9 earthquakes are typically only recorded by instruments.
Authoritative source: USGS event page (event ID: us7000ecrl). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, June 13, 2021). M3.9 Earthquake 72 km S of Nikolski, Alaska — June 13, 2021. Retrieved August 26, 2021 from https://www.earthquaketracker.org/earthquakes/event/us7000ecrl/