M4.2 Earthquake 15 km N of Four Mile Road, Alaska — August 20, 2025
2025-08-20 20:35:27 UTC (2025-08-20) · approx. 10:35 AM UTC-10 local
Felt by 58 people across nearby locations. Maximum shaking intensity MMI 4.0 (moderate).
On August 20, 2025 at 20:35 UTC, a magnitude 4.2 shallow crustal earthquake struck 15 km N of Four Mile Road, Alaska, at a depth of 15.4 km and coordinates 64.7437°, -149.0809°. The earthquake was reported felt by 58 peopleacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 4.0 (moderate).
Physical scale: An earthquake of magnitude 4.2 releases seismic energy equivalent to roughly 30 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 476 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 58 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
-149.0809°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.2 earthquake near Four Mile Road, Alaska?
The magnitude 4.2 earthquake that struck 15 km N of Four Mile Road, Alaska on August 20, 2025 at 20:35 UTC had a depth of 15.4 km. It was felt by 58 people with maximum shaking intensity of MMI 4.0 (moderate). For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 64.7437°, -149.0809°, which is 15 km N of Four Mile Road, Alaska. View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.2 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 4.2 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: ak025ao0swgd). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, August 20, 2025). M4.2 Earthquake 15 km N of Four Mile Road, Alaska — August 20, 2025. Retrieved November 12, 2025 from https://www.earthquaketracker.org/earthquakes/event/ak025ao0swgd/