Thursday 14 September 2017

Magnitude 4.6 Earthquake beneath Saitama Prefecture, Japan.

The Japan Meteorological Agency recorded a Magnitude 4.6 Earthquake at a depth of about 50 km, about 2 km to the southwest of the city of Wakō in Saitama Prefecture on Honshū Island, slightly before 9.30 am Japan Standard Time (slightly before 0.30 am GMT) on Thursday 14 September 2017. There are no reports of any damage or casualties associated with this event, but many people have reported feeling the event across the Kantō region.

The approximate location of the 14 September 2017 Saitama Prefecture Earthquake. USGS.

Japan has a complex tectonic situation, with parts of the country on four different tectonic plates. Eastern Honshū area lies on the boundary between the Pacific, Eurasian and Philippine Plates, where the Pacific Plate is passing beneath the Eurasian and Philippine Plates 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. 

The movement of the Pacific and Philippine Plates beneath eastern Honshū. 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 organisation 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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