M4.7 Earthquake 6 km N of Asahi, Japan — October 28, 2026

On October 28, 2026 at 18:32 UTC, a magnitude 4.7 shallow crustal earthquake struck 6 km N of Asahi, Japan, at a depth of 41.5 km and coordinates 35.7763°, 140.6463°. This earthquake was detected by 129 seismic stations with good location accuracy and was assigned a USGS significance rating of 340, placing it among routine seismic activity.

Physical scale: An earthquake of magnitude 4.7 releases seismic energy equivalent to roughly 169 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 1.1 km — a useful intuition for the size of the slip patch on the fault.

This earthquake is part of an ongoing aftershock sequence following the magnitude 5.5 mainshock that occurred 8 hours ago 5 km ESE of Asahi, Japan. Since the mainshock, the USGS has recorded 3 aftershocks in this area. Aftershock activity is expected to continue for days to weeks as stresses on surrounding faults redistribute.

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