The Japan Meteorological Agency
recorded a Magnitude 6.5 Earthquake at a depth of about 420 km, off the south coast of the Honshū Island,
slightly after 3.30 am Japan
Standard Time on Sunday 28 July 2019 (slightly after 6.30 pm on Saturday 27 July GMT).
The event was felt across much of Honshū Island, though there are no reports of any damage or casualties. This is roughly what
would be expected
from an Earthquake of this size at this depth; the quake is big enough
to be felt over a wide area, but most of its energy has dissipated
before the shock-waves reach the surface.
The approximate location of the 28 July 2019 Honshū 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.
See also...
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