Friday 15 April 2016

Thousands evacuated and at least nine dead following Magnitude 6.4 Earthquake on Kyushu Island, Japan.

At least nine people have died and another 850 have been injured, eight seriously, following an Earthquake on the Japanese island of Kyushu slightly before 9.30 pm Japan Standard Tme (slightly before 12.30 pm GMT) on Thursday 14 April 2016. A further 44 000 people have been evacuated from the area around the town of Mashiki in Kumamoto Prefecture following the event, which was measured by the Japan Meteorological Agency as being a Magnitude 6.4 Earthquake at a depth of 10 km.

A collapsed house in Mashiki, Japan, following the 14 April 2016 Earthquake. AP.

The evacuations have been carried out due to the large number of buildings deemed to be unsafe in the area following the event, and the possibility of aftershocks, which are common following following major events of this kind as rock formations in the surrounding area settle into new positions following a major seismic movement. Concerns have also been raised about the proximaty of the event to a number of active volcanoes. Seismic activity beneath volcanoes can be significant, as they are often caused by the arrival of fresh magma, which may indicate that a volcano is about to undergo an eruptive episode.

 Damage to Kumamoto Castle in Chūō-ku following the 14 April 2016 Earthquake. Yusuke Ogata/AP.

Japan has a complex tectonic situation, with parts of the country on four different tectonic plates. Kyushu Island lies at the northeast end of the Ryukyu Island Arc, which sits on top of the boundary between the Eurasian and Philippine Plates. The Philippine Plate is being subducted beneath the Eurasian Plate, in the Ryukyo Trench, to the Southeast of the Islands. As it is drawn into the interior of the Earth, the tectonic plate is partially melted by the heat of the Earth's interior, and liquid magma rises up through the overlying Eurasian Plate to form the volcanos of the Ryukyu Islands and Kyushu.

 The movement of the Pacific and Philippine Plates beneath eastern Honshu. Laurent Jolivet/Institut des Sciences de la Terre d'Orléans/Sciences de la Terre et de l'Environnement.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organization Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.
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