M4.9 Earthquake 20 km W of Hiroo, Japan — August 18, 2023
2023-08-18 18:33:04 UTC (2023-08-18) · approx. 4:33 AM UTC+10 local
On August 18, 2023 at 18:33 UTC, a magnitude 4.9 shallow crustal earthquake struck 20 km W of Hiroo, Japan, at a depth of 61.2 km and coordinates 42.3156°, 143.0491°. This earthquake was detected by 257 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.
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
143.0491°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.9 earthquake near Hiroo, Japan?
The magnitude 4.9 earthquake that struck 20 km W of Hiroo, Japan on August 18, 2023 at 18:33 UTC had a depth of 61.2 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 42.3156°, 143.0491°, which is 20 km W of Hiroo, 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.
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.
Actions
Location
Authoritative source: USGS event page (event ID: us7000kpb9). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, August 18, 2023). M4.9 Earthquake 20 km W of Hiroo, Japan — August 18, 2023. Retrieved October 27, 2023 from https://www.earthquaketracker.org/earthquakes/event/us7000kpb9/