| 青藏高原东南缘壳幔力学耦合及其动力学意义 |
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| 引用本文： | 侯 强,邹文远,欧明霖,丁小军.青藏高原东南缘壳幔力学耦合及其动力学意义[J].大地测量与地球动力学,2018,38(10):991-1000. |
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| 作者姓名： | 侯 强 邹文远 欧明霖 丁小军 |
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| 摘 要： | 现代大陆动力学及构造学研究认为，壳内软弱带控制着地壳与地幔间相互作用的强弱，制约岩石圈层间的耦合关系，同时也影响地块的相互作用方式。这种耦合作用可以通过比较不同深度的形变和应力的相关特征来分析。青藏高原东南缘20～35 km的深度广泛存在低速带，有可能在现今地震及构造活动区内由壳内部分熔融承担了潜在的解耦功能。基于1999～2015年GPS坐标时间序列数据得到速度场，结合前人给出的SKS剪切波分裂数据，分析该区水平方向形变耦合特征；同时搜集莫霍面和岩石圈底面形变数据，给出垂向上的形变耦合特征。利用EGM2008重力模型的11～36阶球谐系数计算青藏高原东南缘岩石圈底面地幔对流应力场；搜集并整理2000年至今的1 131个震源机制解数据，采用区域应力张量阻尼反演法得到该区多震层应力场；进一步分析两种应力场的相关性。在ABAQUS软件中建立青藏高原东南缘岩石圈三维粘弹性有限元模型，同时加入上地壳的边界位移约束条件和底面地幔对流拖曳力加载条件，分别对水平方向和垂直方向的应力应变作分析，并给出强震剖面结果，探讨壳幔耦合强震孕育机制，据此分析青藏高原东南缘各个断层的地震危险性。研究认为，应力的不均匀发展是应变能积累的关键，同时垂向上圈层间的耦合关系极大地影响块体间的作用方式；壳内软弱带广泛发育的块体应力出现分层现象，边缘区域横向纵向应力变化明显，与之接触的上伏地壳地震危险性较高。
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| 关 键 词： | 青藏高原东南缘 壳幔耦合 孕震机制 有限元模拟 |
Mechanical Coupling in Southeastern Qinghai-Tibetan Plateau and Its Geodynamic Implications |
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| HOU Qiang,ZOU Wenyuan,OU Minglin,DING Xiaojun.Mechanical Coupling in Southeastern Qinghai-Tibetan Plateau and Its Geodynamic Implications[J].Journal of Geodesy and Geodynamics,2018,38(10):991-1000. |
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| Authors: | HOU Qiang ZOU Wenyuan OU Minglin DING Xiaojun |
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| Abstract: | Modern continental dynamics and structure geology have determined that shell with control weak interaction between crust and mantle not only restricts the coupling relationships between the spheres of rock, but also affects the interaction plots. The coupling effect can compare the different depth of the deformation and stress characteristics analysis. The widespread low velocity zones at the depth of 20－35 km in the southeastern margin of the Qinghai-Tibetan plateau may have potential decoupling functions in the present seismic and tectonic activities due to melting from the inner part of the crust. This paper, based on the 2015－1999 GPS coordinate time series data to obtain the velocity field, combined with the previous SKS given shear wave data, analyzes the horizontal deformation coupling characteristics; further it collects the Moho and lithosphere bottom deformation data, showing that the deformation characteristics are vertical upward. The use of EGM2008 gravity model 11－36 order spherical harmonic coefficients are calculated in the Sichuan-Yunnan region under the lithosphere mantle convection stress field, collecting and sorting the 1 131 focal mechanism solutions of the data since 2000, the regional stress tensor inversion method of damping the seismogenic layer stress field of the region; and further analysis of the two kinds of stress field correlation. In the ABAQUS software, the 3D lithospheric viscoelastic finite element model of Sichuan-Yunnan region is established, while adding the upper crust boundary displacement constraints and the bottom surface of the mantle convection drag loading conditions. The stress and strain in horizontal and vertical directions are analyzed respectively, and the results of strong earthquake profile are given. The seismogenic mechanism of crust mantle coupling is discussed, and the seismic risk of faults in Sichuan-Yunnan region is analyzed. Through the above research, the dissertation infers that the uneven development of stress is the key of strain energy accumulation, and vertical coupling relationship between the spheres has greatly influenced the block effect. Further, the shell weak zone blocks the extensive development of stress stratification, the edge area of transverse and longitudinal stress changes high volt, crustal seismic hazard and contact. |
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| Keywords: | southeastern Qinghai-Tibetan plateau crust-mantle mechanical coupling seismogenic mechanism finite element modeling |
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