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The Chūetsu Offshore earthquake ((日本語:平成19 年（2007 年）新潟県中越沖地震)) was a powerful magnitude 6.6 earthquake〔〔(asahi.com：新潟、長野で震度６強 ８人死亡、９０８人がけが – 社会 ) 〕 that occurred 10:13 local time (01:13 UTC) on July 16, 2007, in the northwest Niigata region of Japan. The earthquake, which occurred at a previously unknown offshore fault shook Niigata and neighbouring prefectures. The city of Kashiwazaki and the villages of Iizuna and Kariwa registered the highest seismic intensity of a strong 6 on Japan's ''shindo'' scale, and the quake was felt as far away as Tokyo.〔 Eleven deaths and at least 1000 injuries were reported, and 342 buildings were completely destroyed, mostly older wooden structures.〔〔(Niigata earthquake death toll rises to eleven ) (Japan News Review ), July 23〕 Prime Minister Shinzō Abe broke off from his election campaign in Southern Japan to visit Kashiwazaki and promised to "make every effort towards rescue and also to restore services such as gas and electricity". ==Tectonic summary== This magnitude 6.6 earthquake occurred approximately 17 km off the west coast of Honshū, Japan, in a zone of compressional deformation that is associated with the boundary between the Amur plate and the Okhotsk plate. At this latitude, the Okhotsk Plate is converging to the west-northwest towards the Amur Plate with a velocity of about 9 mm/yr and a maximum convergence rate of 24 mm/yr. The Amur and Okhotsk plate are themselves relatively small plates that lie between the Eurasian Plate and the Pacific Plate. The Pacific plate converges west-northwest towards the Eurasia plate at over 90 mm/yr. Most of the relative motion between the Pacific plate and the Eurasia plate is accommodated approximately 400 km to the east-southeast of the epicenter of the earthquake, where the Pacific plate subducts beneath the Okhotsk plate. This shallow crustal earthquake was followed 13 hours later by a deep focus magnitude 6.8 quake roughly 330 km to the west, 350 km below the Sea of Japan. The two earthquakes were generated by different mechanisms. The first earthquake was caused by deformation within the crust of the Okhotsk plate and the second quake was likely caused by faulting resulting from internal deformation of the subducted Pacific plate. Given their different mechanisms and physical separation of at least 10 rupture lengths, the second earthquake is not considered an aftershock of the first. Shallow earthquakes cause more damage than intermediate- and deep-focus ones since the energy generated by the shallow events is released closer to the surface and therefore produces stronger shaking than is produced by quakes that are deeper within the Earth.〔(Magnitude 6.6 – NEAR THE WEST COAST OF HONSHU, JAPAN )〕 The peak ground acceleration generated was 993 gal (1.01 ''g''). Two days after the initial earthquake, an aftershock occurred, registering 4 shindo in Izumozaki, Niigata〔(Aftershock hits Niigata – Japan News Review )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「2007 Chūetsu offshore earthquake」の詳細全文を読む スポンサード リンク
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