M5.1 Earthquake 86 km S of Koshima, Japan — October 17, 2021
2021-10-17 02:32:07 UTC (2021-10-17) · approx. 11:32 AM UTC+9 local
On October 17, 2021 at 02:32 UTC, a magnitude 5.1 shallow crustal earthquake struck 86 km S of Koshima, Japan, at a depth of 24.6 km and coordinates 29.4559°, 130.6225°.
Physical scale: An earthquake of magnitude 5.1 releases seismic energy equivalent to roughly 674 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 2.0 km — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in Japan, a region characterized by the intersection of four tectonic plates — Pacific, Philippine Sea, Eurasian, and North American — creating multiple subduction zones. The nearest mapped fault system is the Japan Trench. View all earthquakes in Japan.
Learn more: Magnitude scale · Aftershock sequences
Earthquake Details
130.6225°E
Technical Information
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Common Questions
How strong was the magnitude 5.1 earthquake near Koshima, Japan?
The magnitude 5.1 earthquake that struck 86 km S of Koshima, Japan on October 17, 2021 at 02:32 UTC had a depth of 24.6 km. For context, this was a moderate earthquake that could be widely felt.
Where did the earthquake occur?
The earthquake epicenter was located at 29.4559°, 130.6225°, which is 86 km S of Koshima, Japan. View all earthquakes in Japan.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.1 earthquakes can continue for days to weeks and gradually diminish over time.
Has Japan had earthquakes this big before?
The largest recorded earthquake in Japan was the M9.1 Tohoku earthquake of March 11, 2011. Today's magnitude 5.1 event is significantly smaller than that historical record.
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Location
Authoritative source: USGS event page (event ID: us6000fvc3). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, October 17, 2021). M5.1 Earthquake 86 km S of Koshima, Japan — October 17, 2021. Retrieved December 22, 2025 from https://www.earthquaketracker.org/earthquakes/event/us6000fvc3/