区域新构造活动的水下事件沉积响应:以死海盆地和柴达木盆地为例  

Subaqueous event deposits response to regional neotectonics:Case studies of the Dead Sea Basin and the Qaidam Basin

作　　者：卢银 Nadav Wetzler Shmuel Marco 方小敏[4,5] LU Yin;Nadav WETZLER;Shmuel MARCO;FANG Xiaomin(Department of Geology,University of Innsbruck,Innsbruck 6020,Austria;Geological Survey of Israel,Jerusalem 9692100,Israel;Department of Geophysics,Tel Aviv University,Tel Aviv 6997801,Israel;State Key Laboratory of Tibetan Plateau Earth System,Resources and Environment,Institute of Tibetan Plateau Research(TPESRE),Chinese Academy of Sciences,Beijing 100101;Key Laboratory of Continental Collision and Plateau Uplift,Institute of Tibetan Plateau Research,Chinese Academy of Sciences,Beijing 100101)

机构地区：[1]Department of Geology,University of Innsbruck,Innsbruck 6020,Austria [2]Geological Survey of Israel,Jerusalem 9692100,Israel [3]Department of Geophysics,Tel Aviv University,Tel Aviv 6997801,Israel [4]中国科学院青藏高原研究所,青藏高原地球系统资源与环境国家重点实验室,北京100101 [5]中国科学院青藏高原研究所,大陆碰撞与高原隆升重点实验室,北京100101

出　　处：《第四纪研究》2022年第3期617-636,共20页Quaternary Sciences

基　　金：科技部第二次青藏高原综合科学考察研究项目(批准号:2019QZKK0707);中国科学院(A类)战略性先导科技专项项目(批准号:XDA20070201);奥地利科学基金会项目(批准号:M 2817 to Yin Lu)共同资助

摘　　要：自20世纪70年代以来,位于构造活跃区的盆地沉积序列的岩性、粒度与沉积速率的正向突变,常被用来指示区域新构造活动。然而,这种常规方法已经受到国内外学者强有力的质疑——用来推断构造活动的沉积学证据也可由气候因素引起。因而,需寻找某种独立于气候因素的沉积学证据来可靠地指示新构造活动。震积岩,由地震震动引起的、保存于湖相或海相地层序列中的事件沉积,能可靠的指示区域新构造活动。新兴的交叉研究方向——湖泊/海洋古地震学,通过研究保存于水下沉积序列中的震积岩,可延长强震记录,加深对断裂带活动性的认识。文章以死海盆地(中东地区)和柴达木盆地(青藏高原东北缘)为例,从水下事件沉积响应的视角,借助超长尺度的震积岩序列,理解千年-构造尺度上的区域新构造活动特性。基于死海湖心457 m长的ICDP 5017-1岩芯保存的震积岩序列,我们建立了一条由151个M_(W)≥7地震事件组成的,全球最长的(220 ka)连续大地震记录,该记录揭示了缓慢滑动的死海断裂带上的大地震具有聚类式的复发特征,以及不同断层分支相互作用、聚类活动的模式;基于青藏高原东北缘柴达木盆地西部的碱山背斜顶部SG-1b岩芯上部260 m沉积序列,我们建立了一条由164个震积岩层位构成的覆盖3.6~1.6 Ma的震积岩序列,该序列在3.6~2.7 Ma时段内相对较为连续,由126个地震事件和5个地震集合组成,揭示了与强烈区域变形有关的晚上新世幕式逆冲过程。Sharp changes in lithology and increases in grain size and sedimentation rate of sedimentary sequences from tectonically active basins are often used to indicate regional neotectonic activity.However,these conventional methods have been challenged by others who argue that the sedimentary evidence used to infer tectonism could be climatically induced.Therefore,some form of independent evidence or sedimentary criteria are required to discriminate between these two alternatives.Seismites,sedimentary structures preserved in lacustrine or marine stratigraphic sequences caused by seismic shaking,are reliable indicators of regional neotectonic activity.Lacustrine/Marine paleoseismology,an emerging cross-field,can extend the record of strong earthquakes and deepen the understanding of fault zone activity by studying seismites preserved in subaqueous sedimentary sequences.In this paper,we use the Dead Sea Basin and Qaidam Basin as examples to understand regional neotectonic activity from the perspective of subaqueous paleoseismology.The Dead Sea Basin is the deepest and largest continental tectonic structure in the world.A 457 m deep core(ICDP Core 5017-1)was recovered from the Dead Sea depocenter(31°30′29″N,35°28′16″E)during 2010~2011.The bottom of the core was dated back to 220 ka.In situ folded layers and intraclast breccia layer in the core are identified as earthquake indicators,based on their resemblance to the lake outcrop observations of seismites that are known to be earthquake-induced.Based on the Kelvin-Helmholtz instability,we model the ground acceleration needed to produce each seismite by using the physical properties of the Dead Sea deposits.We invert acceleration for earthquake magnitude by considering regional earthquake ground motion attenuation,fault geometry,and other constraints.Based on the magnitude constraints,we develop a 220 ka-long record of MW≥7 earthquakes.The record comprises 151 MW≥7 events.The record shows a clustered earthquake recurrence pattern and a group-fault temporal cl

关 键 词：震积岩 湖泊/海洋事件沉积 湖泊/海洋古地震学 强震复发模式 区域新构造活动特性 

分 类 号：P546[天文地球—构造地质学]