M6.2 Quake Strikes 16 km East of Chiba
Strong Quakes Rattles Large Areas East of Tokyo, Japan
The strong quake, epicentered at 140.39°E, 35.53°N struck at a depth of 28km at 13:37:02 UTC on April 21, GFZ Potsdam reported.
The quake was followed by a number of aftershocks, the largest of which measured 5.6Mw.
FIRE-EARTH forecast: The mean distance of epicenters for significant shocks striking near Boso Triple Junction (Sagami Trough), on the east coast of Honshu, are moving closer to Tokyo area, making Chiba City a highly probable target for a large quake (Magnitude > 8.4Mw).

NGDC/NOAA map of Japan Trench, with the broader location of Boso Triple Junction marked. Map enhanced by FIRE-EARTH.
Earthquake Map

Quake Details
Region: Near East Coast of Honshu, Japan
Magnitude: 6.2Mw
Time: 2011-04-21 13:37:01.9 UTC
Epicenter: 140.39°E, 35.53°N
Depth: 28 km
Source: GFZ Potsdam – Earthquake Bulletin
Japan Meteorological Agency reported the quake as a 6.0Mw, while USGS recorded a 6.1Mw shock. NO tsunami warning/advisory was issued.
Distances [USGS]
- 64 km (39 miles) E of TOKYO, Japan
- 76 km (47 miles) ENE of Yokohama, Honshu, Japan
- 82 km (50 miles) S of Mito, Honshu, Japan
- 115 km (71 miles) SSE of Utsunomiya, Honshu, Japan
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