M4.9 Earthquake 155 km NNE of Hirara, Japan — December 22, 2025
2025-12-22 12:38:09 UTC (2025-12-22) · approx. 8:38 PM UTC+8 local
Aftershock of the M6.1 mainshock.
On December 22, 2025 at 12:38 UTC, a magnitude 4.9 intermediate depth earthquake struck 155 km NNE of Hirara, Japan, at a depth of 90.0 km and coordinates 26.0146°, 126.0921°. This earthquake was detected by 60 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 369, placing it among routine seismic activity.
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.
This earthquake is part of an ongoing aftershock sequence following the magnitude 6.1 mainshock that occurred 8 days ago 136 km NNE of Hirara, Japan. Since the mainshock, the USGS has recorded 1 aftershocks in this area. Aftershock activity is expected to continue for weeks to months 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
Earthquake Details
126.0921°E
Technical Information
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Common Questions
How strong was the magnitude 4.9 earthquake near Hirara, Japan?
The magnitude 4.9 earthquake that struck 155 km NNE of Hirara, Japan on December 22, 2025 at 12:38 UTC had a depth of 90.0 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 26.0146°, 126.0921°, which is 155 km NNE of Hirara, Japan. View all earthquakes in Japan.
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.
Is this the same earthquake as the M6.1 one earlier?
No. This magnitude 4.9 earthquake is an aftershock of the larger magnitude 6.1 mainshock that occurred earlier 136 km NNE of Hirara, Japan. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
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 4.9 event is significantly smaller than that historical record.
What should I do after an earthquake?
If you were in the affected area: check yourself and others for injuries, inspect your home for damage, and be prepared for aftershocks.
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Location
Authoritative source: USGS event page (event ID: us6000rwh8). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, December 22, 2025). M4.9 Earthquake 155 km NNE of Hirara, Japan — December 22, 2025. Retrieved March 19, 2026 from https://www.earthquaketracker.org/earthquakes/event/us6000rwh8/