摘要
在青海都兰最新开展的活动断裂调查工作中,于都兰-茶卡高地南部新发现了1条长约40km、走向近NEE的左旋走滑、局部兼正断性质的全新世活动断裂--热水-桃斯托河断裂。文中通过野外地质调查与典型段落无人机航拍主要获得了以下2点认识:1)热水-桃斯托河断裂及其全新世活动的发现尚属首次,其长约40km,断裂带东端存在长6km的地表破裂带;2)断裂切过的冲沟和阶地存在左旋位错现象,利用无人机获取高分辨率DEM影像,并对冲沟沟谷的地形剖面进行恢复测量得到的位错量为(9.3±0.5)m、(17.9±1.5)m和(36.8±2)m。对2级冲沟阶地位错进行恢复测量得到T1/T0阶地陡坎的位错量为(18.2±1.5)m,T2/T1阶地陡坎的位错量为(35.8±2)m,可以看出冲沟位错量和阶地位错量的结果较为一致。据历史地震记载,1938年4月10日在热水-桃斯托河断裂地表破裂的东端发生了M5地震,1952年3月21日发生了MS5.0地震,可能均与该断裂的活动有关。但在都兰县县志等相关资料中均未发现有关于这2次地震的文献记录,这可能与当时地震震中比较偏远、都兰县人口稀少且发震时间比较久远有关。东昆仑断裂和鄂拉山断裂最南端会聚形成1个向NW挤出的楔形断块,位于楔形断块端部的都兰盆地受区域NE-SW向主压应力和2条边界断裂剪切作用的影响,经历了挤压伴随局部拉张的复杂变形过程。这主要是由于2条控制楔形断块的边界断裂--东昆仑断裂与鄂拉山断裂之间存在NE-SW向的挤压作用,在这样的挤压过程中,楔形断块局部拉张的具体表现形式为两侧断裂发生走滑,使断块向NW向挤出,因此该区三角楔形挤出的变形机制与纯粹的刚性块体的挤出机制有所不同。在靠近鄂拉山断裂的都兰盆地东北缘形成一系列向SE会聚的羽列状逆冲断裂,其形态上向E与鄂拉山断裂平行,可能在深部汇入鄂拉山断裂;靠近东昆仑断裂带的都
The 40 km-long,NEE trending Reshui-Taostuo River Fault was found in the southern Dulan-Chaka highland by recent field investigation,which is a strike-slip fault with some normal component.DEM data was generated by small unmanned aerial vehicle(UAV)on key geomorphic units with resolution<0.05 m.Based on the interpretation and field investigation,we get two conclusions:1)It is the first time to define the Reshui-Taostuo River Fault,and the fault is 40 km long with a 6 km-long surface rupture;2)There are left-handed dislocations in the gullies and terraces cut by the fault.On the high-resolution DEM image obtained by UAV,the offsets are(9.3±0.5)m,(17.9±1.5)m,and(36.8±2)m,measured by topographic profile recovery of gullies.The recovery measurements of two terraces present that the horizontal offset of T1/T0 is(18.2±1.5)m and the T2/T1 is(35.8±2)m,which is consistent with the offsets from gullies.According to the historical earthquake records,a M5earthquake on April 10,1938 and a MS5.0 earthquake on March 21,1952 occurred at the eastern end of the surface rupture,which may be related to the activity of the fault.By checking the county records of Dulan and other relevant data,we find that there are no literature records about the two earthquakes,which is possibly due to the far distance to the epicenter at that time,the scarcity of population in Dulan,or that the earthquake occurred too long ago that led to losing its records.The southernmost ends of the Eastern Kunlun Fault and the Elashan Fault converge to form a wedgeshaped extruded fault block toward the northwest.The Dulan Basin,located at the end of the wedgeshaped fault block,is affected by regional NE and SW principal compressive stress and the shear stress of the two boundary faults.The Dulan Basin experienced a complex deformation process of compression accompanying with extension.In the process of extrusion,the specific form of extension is the strike-slip faults at each side of the wedge,and there is indeed a north-east and south-west compression
作者
李智敏
任治坤
刘金瑞
哈广浩
李正芳
王勃
王林建
LI Zhi-min;REN Zhi-kun;LIU Jin-rui;HA Guang-hao;LI Zheng-fang;WANG Bo;WANG Lin-jian(Qinghai Earthquake Agency,Xining 810001,China;Institute of Geology,China Earthquake Administration,Beijing 100029,China;Shenzhen Academy of Disaster Prevention and Reduction,Shenzhen 518003,China)
出处
《地震地质》
EI
CSCD
北大核心
2020年第1期18-32,共15页
Seismology and Geology
基金
中国地震局地质研究所基本科研业务专项(IGCEA1803)
第二次青藏高原综合科学考察项目(2019QZKK0704)
青海省科技计划项目(2017-ZJ-775)共同资助。
关键词
青藏高原
热水-桃斯托河断裂
左旋位错
地表破裂
全新世活断层
northeastern margin of Tibetan plateau
Reshui-Taostuo River Fault
left-lateral offsets
earthquake surface rupture
Holocene active fault
