M4.5 Earthquake 29 km ESE of Iwaki, Japan — October 20, 2023
2023-10-20 20:55:29 UTC (2023-10-20) · approx. 5:55 AM UTC+9 local
On October 20, 2023 at 20:55 UTC, a magnitude 4.5 shallow crustal earthquake struck 29 km ESE of Iwaki, Japan, at a depth of 36.4 km and coordinates 36.9476°, 141.1834°. This earthquake was detected by 49 seismic stations with good location accuracy and was assigned a USGS significance rating of 312, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 4.5 releases seismic energy equivalent to roughly 85 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 767 m — 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
141.1834°E
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Common Questions
How strong was the magnitude 4.5 earthquake near Iwaki, Japan?
The magnitude 4.5 earthquake that struck 29 km ESE of Iwaki, Japan on October 20, 2023 at 20:55 UTC had a depth of 36.4 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 36.9476°, 141.1834°, which is 29 km ESE of Iwaki, Japan. View all earthquakes in Japan.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.5 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 4.5 event is significantly smaller than that historical record.
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Location
Authoritative source: USGS event page (event ID: us7000l67m). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, October 20, 2023). M4.5 Earthquake 29 km ESE of Iwaki, Japan — October 20, 2023. Retrieved December 26, 2023 from https://www.earthquaketracker.org/earthquakes/event/us7000l67m/