M3.9 Earthquake 18 km E of Ōarai, Japan — September 18, 2026
2026-09-18 21:15:13 UTC (2026-09-18) · approx. 6:15 AM UTC+9 local
On September 18, 2026 at 21:15 UTC, a magnitude 3.9 shallow crustal earthquake struck 18 km E of Ōarai, Japan, at a depth of 43.4 km and coordinates 36.3199°, 140.7901°.
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
140.7901°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 3.9 earthquake near Ōarai, Japan?
The magnitude 3.9 earthquake that struck 18 km E of Ōarai, Japan on September 18, 2026 at 21:15 UTC had a depth of 43.4 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.
Actions
Location
Understanding This Data
Magnitude 3.9 earthquakes are typically only recorded by instruments.
Authoritative source: USGS event page (event ID: us7000tifm). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2026, September 18, 2026). M3.9 Earthquake 18 km E of Ōarai, Japan — September 18, 2026. Retrieved October 23, 2026 from https://www.earthquaketracker.org/earthquakes/event/us7000tifm/