July 11, 2014 Earthquake: Sanriku, Japan

Felt (V) at Iwaki; (IV) at Chiba, Hitachi, Sendai, Tsuchiura, Utsunomiya and Yokohama; (III) at Kawasaki, Narita and Tokyo. Felt widely on Honshu from Nagoya to Hachinohe. Recorded (4 JMA) in Fukushima, Ibaraki, Miyagi and Tochigi.

Tectonic Summary

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.

(above from reference #13456)

On July 12, there was a M7.0 earthquake offshore Fukushima prefecture. This event caused tsunami observed along the coasts from Iwate to Fukushima prefectures, with a height of 17cm at Ayukawa, Ishinomaki city, Miyagi prefecture. This event caused damage with injured persons. (reference #13491)