The Japan Meteorological Agency recorded a Magnitude 6.9 Earthquake at a depth of about 30 km, beneath the Hyūganada Sea, off the coast of Miyazaki Prefecture on Kyūshū Island, Japan, slightly before 9.20 pm Japan Standard Time (slightly before 12.20 pm GMT) on Monday 13 January 2025. One person was slightly injured by the event, due to falling on some stairs, minor damage to several buildings reported, and train services stopped temporarily while lines were checked. A tsunami warning was issued after the initial event, with concerns a wave as high as one metre could be triggered, although in the event a wave only 20 cm high was reported in Miyazaki Port.
Japan has a complex tectonic situation, with parts of the country on four different tectonic plates. Kyūshū Island lies on the margin where the the Eurasian Plate is overiding the Philipine Plate, with the Pacific Plate being subducted beneath the Okhotsk Plate to the east. 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.
Earthquakes along subductive margins are particularly prone to causing tsunamis, since these often occur when the overlying plate has stuck to the underlying plate, being pulled out of shape by its movement. Eventually the pressure builds up to far and the overlying plate snaps back, causing an Earthquake and a tsunami.
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