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先存构造对1985年8月23日新疆乌恰M_w6.9地震地表破裂几何形态和变形样式的制约

Deformation Pattern of the 23 August 1985 Wuqia M_w 6.9 Earthquake Surface Rupture(Xinjiang Province): Control from Inherited Folding-Related Structures

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【作者】 赫洪哲李涛陈杰钱黎

【Author】 He Hongzhe;Li Tao;Chen Jie;Qian Li;Xinjiang Pamir Intracontinental Subduction National Field Observation and Research Station;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration;

【通讯作者】 李涛;

【机构】 新疆帕米尔陆内俯冲国家野外科学观测研究站中国地震局地质研究所,地震动力学国家重点实验室

【摘要】 1985年8月23日发生在新疆维吾尔自治区乌恰县境内的M_w6.9地震,是有地震仪器记录以来,帕米尔-南天山会聚带内发生的最强地震事件之一,也是碰撞造山带前陆地区少数形成显著地表破裂的强震事件之一.在前人研究工作基础上,我们通过对震后Worldview卫星影像、无人机影像、野外调查获得的天然断层露头和人工探槽断层剖面的综合分析,对乌恰地震地表破裂的几何形态、变形样式、下伏断层结构进行了约束.研究表明,地表破裂东段呈弧形展布,其走向、运动性质和下伏断层倾角变化显著;相比较而言,西段虽因后期地表过程改造而非常不连续,其运动性质、走向和下伏断层倾角却更为稳定.由于地表破裂东、西两段分别位于明尧勒背斜南翼向形枢纽的南、北两侧,我们推测这种变形特征的显著差异,可能与向形枢纽两侧先存构造(先存的明尧勒背斜褶皱变形过程中形成的弯滑断层)的发育情况不同有关.

【Abstract】 The 23 August 1985 Wuqia M_w 6.9 earthquake in Xinjiang Province, represents one of the strongest events in the PamirSouthern Tian Shan convergence zone during the instrumental period. It was also one of the few events that produced clear coseismic surface rupture in the mountain ousforeland region. Based on previous studies of Feng et al.(1986, 1988) and Ainscoe(2018), in this study, we investigate map-view geometry, deformation patterns, and subsurface fault geometry of the Wuqia coseismic surface rupture, through a combining analysis of post-seismic Worldview satellite images, drone images, as well as fault outcrops from natural and artificial trench exposures. Our study documents that the eastern segment of the surface rupture exhibits an arcuate shape overall, and its strike, slip sense, and underlying fault dip have a significant variation along the fault.Comparatively, the western segment has more constant trending, slip sense, and underlying fault dip along the fault, even though it is quite discontinuous due to erosion of post-seismic surface process. Given that the eastern and western segments of the surface rupture lies at the southern and northern sidesof a synclinal hinge at Mingyaole southern limb, respectively, we suggest that such contrasting deformation pattern is dominantly controlled by the inherited folding-related structures of the Mingyaole fold(i. e.,flexural-slip faults formed during the Mingyaole folding deformation).

【基金】 国家重点研发计划项目(No.2022YFC3003700);中国地震局地质研究所基本科研业务专项(No.IGCEA1920);第二次青藏高原综合科学考察研究(No.2019QZKK0901)
  • 【分类号】P315
  • 【下载频次】15
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