Strong M6.8 earthquake struck off the east coast of Honshu, Japan

Strong and shallow M6.8 (JMA/EMSC/PTWC) earthquake occurred off the east coast of Honshu, about 129 km ESE of Namie, Japan, at 19:22 UTC on July 11, 2014.  USGS recorded M6.5.

The epicenter was located at coordinates 37.064°N 142.365°E, too far out of the coast to cause significant damage. JMA reported depth of 10 km.

There are no tsunami warnings, only tsunami advisory issued by JMA, advising people to stay of the coastal areas. There are no shaking or tsunami risk for Fukushima.

Pacific Tsunami Warning Center registered M 6.8 at depth of 10 km. No tsunami warnings were issued. (Credit: NOAA/PTWC)

Seismotectonics of Japan and Vicinity

Japan and the surrounding islands straddle four major tectonic plates: Pacific plate; North America plate; Eurasia plate; and Philippine Sea plate. The Pacific plate is subducted into the mantle, beneath Hokkaido and northern Honshu, along the eastern margin of the Okhotsk microplate, a proposed subdivision of the North America plate. Farther south, the Pacific plate is subducted beneath volcanic islands along the eastern margin of the Philippine Sea plate. This 2,200 km-long zone of subduction of the Pacific plate is responsible for the creation of the deep offshore Ogasawara and Japan trenches as well as parallel chains of islands and volcanoes, typical of Circumpacific island arcs. Similarly, the Philippine Sea plate is itself subducting under the Eurasia plate along a zone, extending from Taiwan to southern Honshu that comprises the Ryukyu Islands and the Nansei-Shoto trench.

Subduction zones at the Japanese island arcs are geologically complex and produce numerous earthquakes from multiple sources. Deformation of the overriding plates generates shallow crustal earthquakes, whereas slip at the interface of the plates generates interplate earthquakes that extend from near the base of the trench to depths of 40 to 60 km. At greater depths, Japanese arc earthquakes occur within the subducting Pacific and Philippine Sea plates and can reach depths of nearly 700 km. Since 1900, three great earthquakes occurred off Japan and three north of Hokkaido. They are the M8.4 1933 Sanriku-oki earthquake, the M8.3 2003 Tokachi-oki earthquake, the M9.0 2011 Tohoku earthquake, the M8.4 1958 Etorofu earthquake, the M8.5 1963 Kuril earthquake, and the M8.3 1994 Shikotan earthquake. (USGS) More information on regional seismicity and tectonics

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