M3.6 Earthquake 14 km NW of Glennallen, Alaska — September 14, 2021
2021-09-14 21:51:21 UTC (2021-09-14) · approx. 11:51 AM UTC-10 local
Felt by 16 people across nearby locations.
On September 14, 2021 at 21:51 UTC, a magnitude 3.6 shallow crustal earthquake struck 14 km NW of Glennallen, Alaska, at a depth of 12.0 km and coordinates 62.2137°, -145.7140°. The earthquake was reported felt by 16 peopleacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 3.2 (light).
Physical scale: An earthquake of magnitude 3.6 releases seismic energy equivalent to roughly 3.8 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 184 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
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
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 16 citizen responses to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
Earthquake Details
-145.7140°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 3.6 earthquake near Glennallen, Alaska?
The magnitude 3.6 earthquake that struck 14 km NW of Glennallen, Alaska on September 14, 2021 at 21:51 UTC had a depth of 12.0 km. It was felt by 16 people with maximum shaking intensity of MMI 3.2 (light). For context, this was a minor earthquake typically detected only by instruments.
Where did the earthquake occur?
The earthquake epicenter was located at 62.2137°, -145.7140°, which is 14 km NW of Glennallen, Alaska. View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 3.6 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 3.6 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: ak021btdx9q9). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, September 14, 2021). M3.6 Earthquake 14 km NW of Glennallen, Alaska — September 14, 2021. Retrieved November 23, 2021 from https://www.earthquaketracker.org/earthquakes/event/ak021btdx9q9/