A Magnitude 6.9 Earthquake at a depth of 400 km occurred in the Izu Islands, roughly 600 km to the south of Honshu, slightly before 9.20 am Japan Standard Time (slightly before 0.20 am GMT) on Wednesday 4 September 2013, according to the Japan Meteorological Agency. This is a large Earthquake with the potential to be dangerous, but occurred at considerable depth a long way from any inhabited area, and there are no reports of any damage or casualties, though the quake was felt across much of eastern Honshu.
The approximate location of the 4 September 2013 Izu Islands Earthquake. Google Maps.
The Izu Islands extend southward from the Izu Peninsula on Honshū, along the boundary between the Pacific and Philippine Plates, where the Pacific Plate is passing beneath the Philippine Plate as it is subducted into the Earth. This is not a smooth process; the rocks of the two plates constantly stick together, only to break apart again as the pressure builds up, causing Earthquakes in the process.
See also Japanese city covered in ash by eruption on Sakurajima Volcano, Eruptions on Sakurajima, Magnitude 6.0 Earthquake east of the Oshika Peninsula, Japan, Eruption on Suwanosejima and Eruption on Tori-shima.
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