青藏高原及邻区现今地应变率场的计算及其结果的地球动力学意义  

Computation of the present-day strain rate field of the Qinghai-Tibetan plateau and its geodynamic implications

作　　者：朱守彪[1] 蔡永恩[2] 石耀霖[3] 

机构地区：[1]中国地震局地壳应力研究所,北京100085 [2]北京大学地空学院地球物理学系,北京100871 [3]中国科学院研究生院计算地球动力学实验室,北京100039

出　　处：《地球物理学报》2005年第5期1053-1061,共9页Chinese Journal of Geophysics

基　　金：国家自然科学基金重点项目(40234042);地震科学联合基金项目(103016);北京市自然科学基金项目(8053020)联合资助.

摘　　要：许多研究人员利用GPS测量的速度资料计算了地应变率场,但其结果差异较大.本文将地质统计学中的Kriging方法引入到GPS观测的速度场研究中,通过Kriging插值得到青藏高原及邻区均匀网格节点上的速度值,然后运用有限单元中形函数(Lagrange插值函数)的求导方法,计算每个网格单元积分点处的地应变率分量,从而获得青藏高原及邻区的地应变率场的分布.计算结果显示,青藏高原主体处在南北向受挤压、东西向被拉张的应变状态之中,但高原东部地区则正好相反,即南北向拉张、东西向出现挤压.青藏高原及邻区主应变率的方位与震源机制解中P轴、T轴的方向基本一致;最大主压应变率的高值区分布在喜马拉雅主边界冲断带及附近地区,高原内部出现主张应变率大于压应变率的现象,且高原内部处在拉张应变状态.面膨胀率结果也表明,喜马拉雅山及附近地区为面收缩区,而高原内部其他地区主要为膨胀区;最大剪应变率分布清晰地显示出青藏高原周边的主要断裂带轮廓.文中的应变率计算结果预示青藏高原及周边地区现今的地应变与较长期的地质活动之间有一定的继承关系.Many researchers have calculated strain rates from the same GPS measurement data and obtained different results. In this paper, we introduce the Kriging method in geo-statistics to the study of GPS velocity field. Interpolating the scattered GPS velocity data of the Qinghai-Tibetan plateau and its adjacent areas to grid point values by the Kriging method, we calculate the strain rates from these nodal values of all elements similar to derivatives of shape functions（essential Lagrange interpolation function） in the finite element algorithm, and obtain the distribution of the strain rate field in the Qinghai-Tibetan plateau. The results show that the main part of the Qinghai-Tibetan plateau is in the state of compression in north-south direction, and of extension in the orientation of east-west. On the contrary, in the eastern part of Qinghai-Tibet, the strain rate behaves compressively in east-west and extension in north-south trending. The orientations of principal strain rates are consistent with those of the P axis and T axis in focal mechanisms. The high values of maximum compressive principal strain rates are located in the Himalayan main boundary thrust zone （MBT） and its adjacent regions. The maximum extensional principal strain rate is higher than that of the compressive one in some regions of the interior of the Qinghai-Tibetan Plateau, so the region is in the state of extension. Mso, the surface dilation strain rate shows that it is in the state of surface compression in the Himalayan and its surrounding areas, and it is in the state of surface extension in the interior of the Qinghai-Tibetan Plateau. The distribution of maximum shear strain rates clearly shows the patterns of some main active fault zones. The result of the strain rate in this study suggests that the contemporary, tectonic strain of Tibet inherits the long term geological deformation.

关 键 词：KRIGING方法 GPS观测 地应变率场 青藏高原 

分 类 号：P315[天文地球—地震学] P541[天文地球—固体地球物理学]