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1946 Vancouver Island earthquake : ウィキペディア英語版 | 1946 Vancouver Island earthquake
The 1946 Vancouver Island earthquake occurred with a moment magnitude of 7.3 that struck Vancouver Island, on the Coast of British Columbia, Canada, at 10:15 a.m. on Sunday, June 23.〔 The main shock epicenter occurred in the Forbidden Plateau area northwest of Courtenay. While most of the large earthquakes in the Vancouver area occur at tectonic plate boundaries, the 1946 Vancouver Island earthquake was a crustal event.〔(1946 Vancouver Island Earthquake Anniversary ) Retrieved on 2008-06-11〕 Shaking was felt from Portland, Oregon to Prince Rupert, British Columbia. The earthquake is remembered as one of the most damaging earthquakes in the history of British Columbia. However, damage was restricted because there were no heavily populated areas near the epicenter, where the violent shaking occurred. This earthquake is Canada's largest historic onshore earthquake.〔(The M7.3 Vancouver Island Earthquake of 1946 ) Retrieved on 2008-06-11〕 However, the greatest earthquake in Canadian history recorded by seismometers was the 1949 Queen Charlotte earthquake, an interplate earthquake that occurred on the ocean bottom just off the rugged coast of Graham Island, which reached magnitude 8.1 on the moment magnitude scale.〔(The Magnitude 8.1 Queen Charlotte Island Earthquake of August 22, 1949 ) Retrieved on 2008-06-11〕 == Background and tectonics == The tectonics that caused the 1946 Vancouver Island earthquake are poorly known. No surface expression of the offset was noticed, most likely because the epicenter area is very remote and densely forested. A comprehensive examination and computer interpretation of seismic data from over 50 stations has shown that a possible explanation of the earthquake includes a strike-slip fault corresponding to the lengthy axis of Vancouver Island known as the Beaufort Range Fault. A fault running across Vancouver Island, corresponding to the projection of the underwater Nootka Fault on the British Columbia Coast is also a possibility, but this is less likely to be true, because the earthquake should have given evidence of offsets along a series of highways that follows much of the eastern coastline of Vancouver Island, called Island Highway, and other roads between Courtenay and Campbell River. The estimated depth of the earthquake places it within the continental crust, not at the margin with the Cascadia subduction zone, and certainly not inside the subduction zone itself. Specifically, the earthquake's epicenter was positioned somewhere in the Forbidden Plateau region, located in central Vancouver Island.
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「1946 Vancouver Island earthquake」の詳細全文を読む
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