联合采用定性和定量断层资料的应力张量反演方法及在乌鲁木齐地区的应用  

A grid search method for determination of tectonic stress tensor using qualitative and quantitative data of active faults and its application to the Urumqi area

作　　者：万永革[1] 

机构地区：[1]河北防灾科技学院,河北三河065201

出　　处：《地球物理学报》2015年第9期3144-3156,共13页Chinese Journal of Geophysics

基　　金：中央高校基本科研业务专项资金(创新项目团队资助计划)(ZY20110101);国家科技支撑计划项目(2012BAK19B03-4);国家国际科技合作专项(2012DFR20440)共同资助

摘　　要：地壳应力场是地球动力学研究和地震孕育环境研究的重要基础资料.求解应力场的一种重要方法是根据断层擦痕资料反演,然而擦痕往往难以观测,但断层滑动性质也与应力场有紧密的关系,这部分资料十分丰富.本研究按照应力张量在断层面上的剪应力方向与擦痕滑动方向及断层滑动性质一致为准则提出了联合采用擦痕数据和定性断层滑动数据求解应力场的网格搜索法,并给出了反演参数的一定置信度下的置信区间.采用假定的走滑型、挤压型和拉张型应力张量产生由7个擦痕数据和80个定性断层滑动数据组成的三组数据集.采用这些人工合成数据求解应力张量的实验结果表明,该方法可以更为准确地反演应力张量参数,定性断层滑动资料的参与使得应力张量的主应力方向更加接近假定的主应力方向,并且,应力张量参数的不确定性大大减小.将该方法应用于乌鲁木齐附近的定量擦痕和定性断层滑动性质数据,得到该地区较为精确的应力张量.结果表明,乌鲁木齐主压应力方向为近南北向、主张应力方向近垂直向,应力形因子为0.03.该地区占主导地位的近东西向的逆冲断层是近南北向挤压和近垂直向拉张形成的.较低的应力形因子表明乌鲁木齐地区在南北向挤压并辅以博罗科努山和博格达山的东、西向挤压的应力状态下处于隆升状态.Crustal stress field is fundamental information in studying earthquake dynamics and seismogenic environments.One of methods to determine stress tensors is to fit observed striation.But such data are seldemly measured in geological field investigations.The sense of fault slip（such as thrust fault or normal faulting,left lateral or right lateral strike-slip faulting）is also tightly associated with the stress tensor,which are abundantly obtained from geological field work.So in the case that striation data are too little to constrain the stress tensor,the dataof fault slip can be used to attain this aim.This study attempted to combine the two kinds of data（striation data and fault slip data）to determine stress tensors in a certain area.We analyzed the stress tensor representation in the north-east-down coordinate system,which is composed of three principal stress axes.The stress tensor is represented by 4parameters,3of which give stress directions of the stress tensor and the other one gives the stress shape ratio.We also gave the criteria of fitting the striation data and sense of fault slip with the determined stress tensors.By using agrid search strategy,we provided a method to invert the stress tensors by combination of striation and fault slip data.The confidence itervals of the inverted stress tensors under a certain confidence level were determined by the F-test.Assuming the certain stress tensors of thrust,normal and strike-slip stress regimes,we generated 3sets of data including 7striations and 80 fault slip＂data＂,the strike and dip of which were randomly generated,the rake（for striation）and nature（qualitative data）of which were determined by the corresponding stress tensors with a certain level of ＂noise＂.By using the artifical＂data＂,we inverted the stress tensors by only striation ＂data＂and the hybrid ＂data＂composed of striation ＂data＂and fault slip ＂data＂,respectively.The results show that the principal stress directions determined by the hybrid ＂data＂are c

关 键 词：地壳应力张量 擦痕 定性断层滑动 置信度 

分 类 号：P315[天文地球—地震学]