The 11 a.m. quake measured a preliminary magnitude of 6.6 in waters near Torishima Island, at the southern end of the chain, and occurred at a depth of 10 kilometers. The uninhabited island is located about 580 km south of Tokyo.
The Japan Meteorological Agency said a 1-meter tsunami could have been expected to arrive at parts of the chain at around 11:30 a.m.
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