M4.9 Earthquake 104 km SSE of Sand Point, Alaska — October 20, 2020
2020-10-20 08:18:41 UTC (2020-10-20) · approx. 9:18 PM UTC-11 local
On October 20, 2020 at 08:18 UTC, a magnitude 4.9 shallow crustal earthquake struck 104 km SSE of Sand Point, Alaska, at a depth of 27.8 km and coordinates 54.5020°, -159.7452°.
Physical scale: An earthquake of magnitude 4.9 releases seismic energy equivalent to roughly 338 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 1.4 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
Earthquake Details
-159.7452°E
Technical Information
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Common Questions
How strong was the magnitude 4.9 earthquake near Sand Point, Alaska?
The magnitude 4.9 earthquake that struck 104 km SSE of Sand Point, Alaska on October 20, 2020 at 08:18 UTC had a depth of 27.8 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 54.5020°, -159.7452°, which is 104 km SSE of Sand Point, Alaska. View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.9 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 4.9 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: us6000c9x1). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2020, October 20, 2020). M4.9 Earthquake 104 km SSE of Sand Point, Alaska — October 20, 2020. Retrieved December 29, 2020 from https://www.earthquaketracker.org/earthquakes/event/us6000c9x1/