Sciency Thoughts: Miyagi Prefecture

Monday, 3 May 2021

Magnitude 6.6 Earthquake off the coast of Miyagi Prefecture, Japan.

The Japan Meteorological Agency recorded a Magnitude 6.8 Earthquake at a depth of about 60 km, about 40 km off the east coast of Miyagi Prefecture, on Honshū Island, slightly before 10.30 am Japan Standard Time (slightly before 1.30 am GMT) on Saturday 1 May 2021. The event was felt across much of eastern Japan, and though there are no reports of any serious damage or casualties, train services were suspended for several hours following the quake, and seismologists are warning there is a risk of large aftershocks occurring over the next few weeks.

The approximate location of the 1 May 2021 Miyagi 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.

Magnitude 5.8 Earthquake on the east coast of Miyagi Prefecture, Japan.

The Japan Meteorological Agency recorded a Magnitude 5.8 Earthquake at a depth of about 60 km, on the coast of the Miyagi Peninsula on Honshū Island, slightly before 6.45 am on Saturday 12 November 2016 Japan Standard Time (slightly before 9.45 pm on Friday 11 November GMT). There are no reports of any damage or casualties associated with this event, people have reported feeling it across most of northern and eastern Honshū.

Map showing the location of the 12 November 2016 Miyagi Prefecture Earthquake, and areas where the event was felt. Japan Meteorological Agency.

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 Philipine Plates, where the Pacific Plate is passing beneath the Eurasian and Philipine 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 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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