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首页> 外文期刊>Bulletin of the Seismological Society of America >Northeastern extension of the New Madrid North fault, New Madrid seismic zone, central United States
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Northeastern extension of the New Madrid North fault, New Madrid seismic zone, central United States

机译：美国中部新马德里地震带新马德里北断层的东北扩展

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摘要

Analysis of electric and geologic logs of 517 shallow wells (91 m, 300 ft deep) in southeastern Missouri has revealed a subsurface structural high (herein called the Charleston Uplift) trending N46°E from near New Madrid, Missouri, to Cairo, Illinois, that juxtaposes Paleocene Flour Island Formation against Eocene Claiborne Group. The Charleston Uplift is 30 km (19 miles) long, 7.2 km (4.5 miles) wide, and has a relief of 36 m (120 ft) at the unconformity surface between the Paleogene and Quaternary sections. Two seismic-reflection soundings, one conducted north of the uplift, and the second conducted within the uplift indicate 60 m (198 ft) of apparent structural relief on the underlying top of the Paleozoic, 47 m (155 ft) on the top of the Late Cretaceous, and 19 m (63 ft) on a Tertiary reflector. The Charleston Uplift is interpreted to be the northeastern extension of the New Madrid North fault of the New Madrid seismic zone and locally the western margin fault zone of the Reelfoot rift. Although no surface faulting has been mapped along the Charleston Uplift, the uplift appears to have influenced the Holocene course of the Mississippi River and displaced the Paleocene/Quaternary unconformity, thus indicating Quaternary displacement of the Charleston Uplift across southeastern Missouri, which may continue beneath the Ohio River valley into adjacent Illinois and Kentucky. Thus, the Charleston Uplift strongly suggests Quaternary structural continuity between the Reelfoot rift and Rough Creek graben of Kentucky. Although currently seismically quiet, the 12 February 2012 M 3.9 earthquake and probably the 31 October 1895 ~M 6.6 Charleston earthquake occurred on this structure, thereby illustrating the seismic potential of this structure and extending the New Madrid North fault system at least 30 km (19 miles).
机译：对密苏里州东南部的517口浅井（91 m，300 ft深）的电和地质测井进行分析后发现，地下密实结构高处（此处称为查尔斯顿隆起）呈N46°E趋势，从密苏里州新马德里附近到伊利诺伊州开罗，将新世面粉岛形成与始新世克莱伯恩集团并列。查尔斯顿隆起长30公里（19英里），宽7.2公里（4.5英里），在古近纪与第四纪之间的不整合面处有36 m（120英尺）的起伏。两次地震反射测深，一次在隆起以北进行，第二次在隆起以内进行，表明古生界底层顶部有60 m（198 ft）的表观结构浮雕，在古生界顶部有47 m（155 ft）。白垩纪晚期，三级反射器上19 m（63 ft）。查尔斯顿隆起被解释为新马德里地震带的新马德里北断裂带的东北延伸，以及雷尔富特裂谷的西缘断裂带局部。尽管查尔斯顿隆起未发现地表断层，但该隆起似乎影响了密西西比河的全新世走向，并取代了古新世/第四纪不整合面，从而表明查尔斯顿隆起的第四纪位移横穿了密苏里州东南部，并可能继续在密苏里州南部发生。俄亥俄河谷进入相邻的伊利诺伊州和肯塔基州。因此，查尔斯顿隆起强烈暗示了Reelfoot裂谷和肯塔基州的Rough Creek en陷之间的第四纪构造连续性。尽管目前地震平静，但该结构发生了2012年2月12日的M 3.9级地震，可能还有1895年10月31日〜查尔斯顿M 6.6级地震，从而说明了该结构的地震潜力，并将新马德里北断裂系统扩展了至少30 km（19英里）。

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