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|magnitude = 6.5–7.0 (est) 〔 |location = 〔 |type = Unknown |countries affected = Pacific Northwest |intensity = VIII (''Severe'') |casualties = None }} The 1872 North Cascades earthquake occurred at in northern Washington state on December 15. A maximum Mercalli intensity of VIII (''Severe'') was assessed for several locations, though less intense shaking was observed at many other locations in Washington, Oregon, and British Columbia. Some of these intermediate outlying areas reported V (''Moderate'') to VII (''Very Strong'') shaking, but intensities as high as IV (''Light'') were reported as far distant as Idaho and Montana. Due to the remote location of the mainshock and a series of strong aftershocks, damage to man made structures was limited to a few cabins close to the areas of the highest intensity. Because the earthquake occurred before seismometers were operating in the region, the magnitude of the shock and its location were never precisely determined, but the intensity reports that are available for the event were studied, and various epicenters for the event were proposed based on these limited data. One study presented an estimated moment magnitude of 6.5–7.0, with a proposed location on the east side of the Cascade Range near Lake Chelan. The results of a separate study indicated that it may have been a larger event, placing the shock in the North Cascades, just south of the Canada–United States border at Ross Lake. ==Preface== The Cascadia subduction zone rarely influences the western portion of Washington state, but the November 1873 M7.3 shock near the California–Oregon border may have been associated with it. Although activity in the Pacific Northwest (especially west of the Cascades in Washington) has occasionally been located near the subduction zone, earthquakes there (1949 Olympia, 1965 Olympia, 2001 Nisqually) have mostly been intraslab events. A large M7 earthquake on the Seattle Fault in 900 C.E. may have generated a tsunami in Puget Sound. The 1872 event east of the cascades is not understood well due to the lack of instrumental records and reliable felt intensity reports. 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「1872 North Cascades earthquake」の詳細全文を読む スポンサード リンク
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