吴中海, 周春景, 冯卉, 张克旗, 李家存, 叶培盛, 李跃华, 田婷婷. 2014: 青海玉树地区活动断裂与地震. 地质通报, 33(4): 419-469.
    引用本文: 吴中海, 周春景, 冯卉, 张克旗, 李家存, 叶培盛, 李跃华, 田婷婷. 2014: 青海玉树地区活动断裂与地震. 地质通报, 33(4): 419-469.
    WU Zhong-hai, ZHOU Chun-jing, FENG Hui, ZHANG Ke-qi, LI Jia-cun, YE Pei-sheng, LI Yue-hua, TIAN Ting-ting. 2014: Active faults and earthquake around Yushu in eastern Tibetan Plateau. Geological Bulletin of China, 33(4): 419-469.
    Citation: WU Zhong-hai, ZHOU Chun-jing, FENG Hui, ZHANG Ke-qi, LI Jia-cun, YE Pei-sheng, LI Yue-hua, TIAN Ting-ting. 2014: Active faults and earthquake around Yushu in eastern Tibetan Plateau. Geological Bulletin of China, 33(4): 419-469.

    青海玉树地区活动断裂与地震

    Active faults and earthquake around Yushu in eastern Tibetan Plateau

    • 摘要: 青海玉树是巴颜喀拉地块西南边界上的典型历史强震区。最新的活动断裂遥感解译与地表调查结果表明,该区新构造期间主要发育清水河断裂带、玉树断裂带、阿布多断裂带和杂多断裂带4条NW向左旋走滑活动断裂带。其中,构成玉树—鲜水河—小江断裂系尾端构造的玉树活动断裂带是该区活动性最显著的岩石圈断裂。该断裂是由当江断裂、结古—结隆断裂和巴塘断裂3条斜接的主干断层和夹杂其间的多条次级断裂所共同构成的Z型左旋剪切张扭性变形带。它在上新世以来和晚第四纪期间的左旋走滑速率为4.0~5.4mm/a,调节了该区大部分的块体挤出与旋转变形,并构成该区大震活动的主要控震构造。历史强震梳理和古地震研究揭示,玉树主干走滑断裂带自约14530a BP以来至少发生了包括2010年地震在内的共11次大地震,原地重复间隔平均在千年以上,最长达近3000a。1738年玉树西北地震之后,玉树—甘孜断裂带的主干断层表现为平均间隔为50~100a的低频、串联式分段破裂过程,并且大震活动存在从东南向西北迁移的趋势。通过对玉树断裂未来大地震危险性进行综合地质判定认为,该区至少仍存在6段未来百年内大地震危险程度不同的地震空区,潜在的大地震震级为Mw6.6~7.3,其中危险性相对较高的段落主要是当江断裂带的当江—拉则段和结古—结隆断裂带上的结隆—叶卡诺段与桑卡—相古段。

       

      Abstract: Yushu area in Qinghai Province is located in the typical historical strong earthquake zone of the southwest border of Bayan Har block in eastern Tibetan Plateau. Recent remote sensing images interpretation and surface survey of regional active faults show that there are four NW-trending left strike-slip active fault belts, i.e., Qingshuihe fault zone, Yushu fault zone, Abuduo fault and Zadoi fault from north to south. The Yushu fault zone is a lithospheric fault, which constitutes the end structure of Yushu-Xianshuihe-Xiaojiang fault system, and its activity was the most significant among four belts during Quaternary. Yushu fault is a typical Z-shaped sinistral shear deformation belt which is composed of three en echelon major strong active fault zones, i.e., Dangjiang fault, Jiegu-Jielong fault and Sangka-Chawukou fault from northwest to southeast, and many secondary weak active faults. The sinistral strike-slip rate of Yushu fault has been steady at about 4.0~5.4mm/a since Pliocene and late Quaternary, and adjusted the most rotation and extrusion deformation of Qiangtang-Qamdo block on the south side of Bayan Har block. So Yushu fault also forms the main seismogenic structure which controls the activity of large earthquakes (Mw≥6.8) in Yushu area. The analytical results of historical earthquake and paleo-earthquake study reveal that at least eleven large earthquake events, including the 2010 Yushu earthquake, have occurred along Jielong-Chawukou segment of Yushu fault zone since about 14530a BP. The in situ average occurrence interval is about millennium, and the maximum interval is up to ca. 3000a. However, after the 1738 earthquake that occurred in northwestern Yushu, the large earthquake event migrated at low frequency along major different segments of Yushu-Garzê fault zone at 50~100a cycle from southeast to northwest. Comprehensive earthquake geological analysis yielded a preliminary result of seismic hazard assessment on Yushu fault zone, which suggests that there are at least six seismic gaps in Yushu fault zone, which obviously make up potential large earthquake hazard in recent future of about one hundred years, and the potential earthquake magnitude is about Mw6.6~7.3. Among six seismic gaps, the relatively higher hazard sections are Dangjiang-Laze segment of Dangjiang fault and Jielong-Yekanuo segment of Jiegu-Jielong fault zone.

       

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