M4.9 Earthquake 121 km E of Miyako, Japan — January 6, 2021
2021-01-06 19:13:29 UTC (2021-01-06) · approx. 5:13 AM UTC+10 local
Aftershock of the M5.1 mainshock.
On January 6, 2021 at 19:13 UTC, a magnitude 4.9 shallow crustal earthquake struck 121 km E of Miyako, Japan, at a depth of 26.8 km and coordinates 39.8411°, 143.3322°.
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 5.1 mainshock that occurred 2 days ago 108 km ENE of Miyako, Japan. Since the mainshock, the USGS has recorded 1 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
Earthquake Details
143.3322°E
Technical Information
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Common Questions
How strong was the magnitude 4.9 earthquake near Miyako, Japan?
The magnitude 4.9 earthquake that struck 121 km E of Miyako, Japan on January 6, 2021 at 19:13 UTC had a depth of 26.8 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 39.8411°, 143.3322°, which is 121 km E of Miyako, 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 M5.1 one earlier?
No. This magnitude 4.9 earthquake is an aftershock of the larger magnitude 5.1 mainshock that occurred earlier 108 km ENE of Miyako, 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.
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Authoritative source: USGS event page (event ID: us6000d68y). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, January 6, 2021). M4.9 Earthquake 121 km E of Miyako, Japan — January 6, 2021. Retrieved March 13, 2021 from https://www.earthquaketracker.org/earthquakes/event/us6000d68y/