The Japan Meteorological Agency recorded a Magnitude 6.8 Earthquake at a depth of 10 km, roughly 325 km east of the Fukushima coast of Japan, at about 2.10 am Japan Standard Time on Saturday 26 October 2013 (about 5.10 pm on Friday 25 October, GMT). While this is a very large quake, it was a long way from shore, and no casualties or damage have been reported, though it was felt across much of eastern Honshū and Hokkaido. Large Earthquakes off the east coast of Japan are notorious for producing tsunamis, such as the one which destroyed the Fukushima Daiichi Nuclear Power Plant in March 2011, though predicting the occurrence and size of these can be extremely difficult. On this occasion the Japan Meteorological Agency issued a tsunami alert to low-lying regions, predicting a wave at most 1m high, and a 30 cm wave eventually reached the shore.
The approximate location of the 26 October 2013 Japan Earthquake. Google Maps.
Japan has a complex tectonic situation, with parts of the country on four different tectonic plates. To the east of northern Honshū lies the Japan Trench, along which the Pacific Plate is being subducted beneath the Okhotsk Plate which underlies northern Japan, passing under the island as it sinks into the Earth. This is not a smooth process, the two plates continuously stuck together then broke apart as the pressure built up, causing Earthquakes in the process.
See also Eruption and pyroclastic flow on Sakurajima, Kyushu, Magnitude 5.8 Earthquake in Fukushima Prefecture, Japan, Magnitude 6.9 Earthquake in the Izu Islands to the south of Japan, Eruptions on Sakurajima and Magnitude 6.0 Earthquake east of the Oshika Peninsula, Japan.
Follow Sciency Thoughts on Facebook.