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The occurred at 17:14 local time (08:14 UTC) on 12 June. It had a magnitude of 7.7,〔(【引用サイトリンク】title=Significant Earthquakes of the World 1978 )〕 JMA magnitude 7.4,〔 and triggered a small tsunami. The earthquake reached a maximum intensity of Shindo 5 in Sendai and caused 28 deaths and 1,325 injuries. ==Geology== The northeastern part of Honshū lies above the subduction zone that forms the Japan Trench, where the Pacific Plate is being subducted beneath the Okhotsk Plate.〔 The rupture of the plate interface that caused the earthquake, occurred in two distinct stages, from study of surface and body wave data and the distribution of aftershocks. The first stage of rupture propagated northwards, roughly parallel to the trench axis, along the upper of the two aftershock zones. The second stage began after about 11 seconds with a second shock, about 30 km westward of the first, at the base of the upper aftershock zone, propagating down dip. The cause of this rupture sequence is thought to be the presence of a barrier, a zone of higher strength, between the two aftershock zones. Earthquakes with similar magnitudes have occurred in this region periodically, about every 40 years. Such earthquakes include the ones that occurred in 1793, 1835, 1861, 1897, 1936, and 1978.〔(【引用サイトリンク】url=http://www.jishin.go.jp/main/chousa/00nov4/miyagi.htm )〕 The 2005 Miyagi earthquake is not considered to be the one that was expected to follow the 1978 Miyagi earthquake.〔(【引用サイトリンク】url=http://www.jishin.go.jp/main/chousa/05aug_miyagi/index.htm )〕 More recent comparisons have confirmed the differences between the 1978 and 2005 events but called into question whether this sequence truly represents the repeat of a characteristic earthquake. The rupture zone of the 1978 earthquake occurred at the westernmost limit of known interplate earthquakes, some 150 km back from the trench. This deepest part of the rupture zone, about 40 km, is interpreted to represent the depth of transition to aseismic creep on the plate interface. The maximum peak ground acceleration recorded was 0.125g There was a foreshock of magnitude Mj 5.8 at 17:06 local time, minutes before the main shock.〔http://cais.gsi.go.jp/KAIHOU/report/kaihou21/02_14.pdf〕 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「1978 Miyagi earthquake」の詳細全文を読む スポンサード リンク
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