M3.9 Earthquake 10 km S of Tomakomai, Japan — August 31, 2021
2021-08-31 20:21:10 UTC (2021-08-31) · approx. 5:21 AM UTC+9 local
On August 31, 2021 at 20:21 UTC, a magnitude 3.9 intermediate depth earthquake struck 10 km S of Tomakomai, Japan, at a depth of 106.8 km and coordinates 42.5469°, 141.6087°.
Physical scale: An earthquake of magnitude 3.9 releases seismic energy equivalent to roughly 11 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 296 m — a useful intuition for the size of the slip patch on the fault.
Earthquake Details
141.6087°E
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Common Questions
How strong was the magnitude 3.9 earthquake near Tomakomai, Japan?
The magnitude 3.9 earthquake that struck 10 km S of Tomakomai, Japan on August 31, 2021 at 20:21 UTC had a depth of 106.8 km. For context, this was a minor earthquake typically detected only by instruments.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 3.9 earthquakes can continue for several days and gradually diminish over time.
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Understanding This Data
Magnitude 3.9 earthquakes are typically only recorded by instruments.
Authoritative source: USGS event page (event ID: us7000f9dw). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, August 31, 2021). M3.9 Earthquake 10 km S of Tomakomai, Japan — August 31, 2021. Retrieved November 6, 2021 from https://www.earthquaketracker.org/earthquakes/event/us7000f9dw/