M4.8 Earthquake 157 km E of McCarthy, Alaska — August 6, 2023
2023-08-06 20:22:04 UTC (2023-08-06) · approx. 11:22 AM UTC-9 local
Felt by 7 people across nearby locations. Maximum shaking intensity MMI 6.1 (very strong).
On August 6, 2023 at 20:22 UTC, a magnitude 4.8 shallow crustal earthquake struck 157 km E of McCarthy, Alaska, at a depth of 3.0 km and coordinates 61.3461°, -139.9737°. The earthquake was reported felt by 7 peopleacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 6.1 (very strong). This earthquake was detected by 148 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 357, 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
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 7 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
-139.9737°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.8 earthquake near McCarthy, Alaska?
The magnitude 4.8 earthquake that struck 157 km E of McCarthy, Alaska on August 6, 2023 at 20:22 UTC had a depth of 3.0 km. It was felt by 7 people with maximum shaking intensity of MMI 6.1 (very strong). For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 61.3461°, -139.9737°, which is 157 km E of McCarthy, 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: us6000kybs). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, August 6, 2023). M4.8 Earthquake 157 km E of McCarthy, Alaska — August 6, 2023. Retrieved October 17, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000kybs/