| 青藏高原南缘2015年尼泊尔MW7.8地震发震构造 |
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| 引用本文： | 杨晓平,吴果,陈立春,李传友,陈晓莉.青藏高原南缘2015年尼泊尔MW7.8地震发震构造[J].地球物理学报,2016,59(7):2528-2538. |
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| 作者姓名： | 杨晓平 吴果 陈立春 李传友 陈晓莉 |
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| 作者单位： | 1. 中国地震局地质研究所, 活动构造与活动火山重点实验室, 北京 100029;2. 中国地震局地质研究所, 北京 100029 |
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| 基金项目： | 自然科学基金项目"甘肃北山旧井地区活动断裂的形成及其地震危险性评价"(41572195)、援尼泊尔成套项目地震地质灾害评估和国家科技支撑计划特大地震活动背景研究专题(2012BAK15B01-02)共同资助. |
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| 摘 要： | 2015年4 月25 日尼泊尔MW7.8特大地震发生在喜马拉雅山南麓, 震源机制解表明该地震为低角度逆冲型地震.通过收集地震区的活动构造研究资料、卫星影像解释和野外实地考察,认为尼泊尔MW7.8地震区地表分布三条主要的逆冲断裂,由北向南分别为喜马拉雅主中央断裂(MCT)、喜马拉雅主边界断裂(MBT)和喜马拉雅主前缘断裂(MFT).主边界断裂和主前缘断裂为晚更新世以来的活动断裂,但至今为止也没有发现喜马拉雅主中央断裂晚第四纪活动的依据.野外调查未发现尼泊尔MW7.8地震在喜马拉雅山南麓的主要断裂上形成地震地表破裂带.喜马拉雅山南麓的构造特征为薄皮构造,表现为浅部陡倾断坡-深部缓倾断坪(7°左右)-深部断坡(11°左右)的构造样式.深部断坡-断坪又称为主喜马拉雅断裂(MHT),其中的深部断坡是尼泊尔地震主震(MW7.8)和最大余震(MW7.3)的发震构造.余震大致沿北西向的高喜马拉雅山前缘呈条带状分布,主要分布在低喜马拉雅山区内.剖面上,余震大致分布在主喜马拉雅断裂的上盘推覆体内,推测尼泊尔MW7.8地震时深部断坡发生错动,其地震位移沿深部断坡-断坪向南传播引起上盘的褶皱带缩短变形,进而触发低喜马拉雅和次喜马拉雅褶皱带内产生次级破裂从而产生余震.
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| 关 键 词： | 尼泊尔MW7.8地震 逆冲构造系统 断坡-断坪 主喜马拉雅断裂 发震构造 |
| 收稿时间： | 2015-10-21 |
The seismogenic structure of the April 25, 2015 MW7.8 Nepal earthquake in the southern margin of Qinghai-Tibetan Plateau |
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| YANG Xiao-Ping,WU Guo,CHEN Li-Chun,LI Chuan-You,CHEN Xiao-Li.The seismogenic structure of the April 25, 2015 MW7.8 Nepal earthquake in the southern margin of Qinghai-Tibetan Plateau[J].Chinese Journal of Geophysics,2016,59(7):2528-2538. |
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| Authors: | YANG Xiao-Ping WU Guo CHEN Li-Chun LI Chuan-You CHEN Xiao-Li |
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| Institution: | 1. Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China;2. Institute of Geology, China Earthquake Administration, Beijing 100029, China |
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| Abstract: | The April 25, 2015 MW7.8 Nepal earthquake, with focal mechanism of low-angle thrust, occurred in the southern margin of Qinghai-Tibatan Plateau. Through collecting research data of active structures, satellite image interpretation and field work, three major thrust faults are determined in the seismic region. They are Himalaya Main Central Thrust (MCT), Main Boundary Thrust (MBT) and Main Frontal Thrust (MFT) from north to south respectively. The first one is inactive in the late Quaternary while the latter two are both late Pleistocene active faults. Earthquake surface rupture zone cannot be found in the MW7.8 earthquake. The structural feature of the southern margin of Himalaya is thin-skinned structure, with tectonic style of shallow steep ramp-deep low angle flat (about 7°) -deep ramp (about 11°). The deep ramp-flat is also called Main Himalaya Thrust (MHT), where the deep ramp is seismogenic structure of the main shock (MW7.8) and the maximum aftershock (MW7.3). Aftershocks are banded distribution along the high Himalayan range front with northwestern direction, mainly in the range of low Himalaya mountainous area. It can be found from the profile that aftershocks almost spread in the nappe of the hanging wall of MHT. We make the assumption that when the fault ruptured during the MW7.8 earthquake, seismic displacement propagated along deep ramp-flat from north to south resulting in the shortening deformation of the fold belt in the hanging wall, which further triggering secondary ruptures and much more aftershocks. |
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| Keywords: | MW7 8 Nepal earthquake Thrust system Ramp-flat Main Himalaya Thrust Seismogenic structure |
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