M4.2 Earthquake 3 km WSW of Koshigaya, Japan — June 19, 2023
2023-06-19 23:44:40 UTC (2023-06-19) · approx. 8:44 AM UTC+9 local
On June 19, 2023 at 23:44 UTC, a magnitude 4.2 shallow crustal earthquake struck 3 km WSW of Koshigaya, Japan, at a depth of 62.6 km and coordinates 35.8745°, 139.7498°.
Physical scale: An earthquake of magnitude 4.2 releases seismic energy equivalent to roughly 30 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 476 m — 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 5.8 mainshock that occurred 6 days ago 4 km N of Toride, Japan. Since the mainshock, the USGS has recorded 0 aftershocks in this area. Aftershock activity is expected to continue for days to weeks as stresses on surrounding faults redistribute.
Earthquake Details
139.7498°E
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Common Questions
How strong was the magnitude 4.2 earthquake near Koshigaya, Japan?
The magnitude 4.2 earthquake that struck 3 km WSW of Koshigaya, Japan on June 19, 2023 at 23:44 UTC had a depth of 62.6 km. For context, this was a light earthquake commonly felt near the epicenter.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.2 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M5.8 one earlier?
No. This magnitude 4.2 earthquake is an aftershock of the larger magnitude 5.8 mainshock that occurred earlier 4 km N of Toride, Japan. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
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Understanding This Data
Magnitude 4.2 earthquakes are often felt but rarely cause damage.
Authoritative source: USGS event page (event ID: us6000kngb). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, June 19, 2023). M4.2 Earthquake 3 km WSW of Koshigaya, Japan — June 19, 2023. Retrieved August 26, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000kngb/