川滇地区地壳精细结构与地震孕育深部环境研究

Sichuan-Yunnan Region is profoundly influenced by the collision of the Indian and Euroasian plates for a long time ,tectonic activities appearing intensely, so that Sichuan-Yunnan Region is a natural experimental field of the continent-continent collision for understanding orogenic process.However,due to the geological tectonic background of the region is very extraordinary and complicated, there are always serveral competing recognition about geodynamic models,such as as rigid-block extrusion, continuous deformation, and the mid-lower crustal flow.The present-day research achievements,mainly resulted from resolution limitation,couldn't decipher lithospheric structure and material compositions in the devolopment of continent-continent collision,especially the middle to lower crust.In this project, we plan to make use of the data of the ChinaArray Program I and the fixed seismic stations which are recorded at Sichuan-Yunnan Region,to carry out nonlinear joint inversion with the related seismic observation data of receiver function, Rayleigh wave dispersion and ellipticity (Z/H ratio) by the direct seach method of NA(Neighborhood Algorithm).At the same time, fully taking the influence of imaging deep structure derived from the shallow structure of sedimentary basin into account we further conduct the much more practical signifcance work. For example removing sedimentary effect of receiver function, and so on. On the basis of such work, we can extract the 3D Velocity models and the deep crustal information such as crustal thickness and possion ration et al., and reconstruct the refined strcture of crust, making a forword step to survey the deformational features of the cruastal tectonics. The purpose of the proposal, on the one hand, is providing reliable geophysical references for the continental dynamics and the deep environment of seismogenesis, on the other hand sastifying for the requirement of seismic prevention and disaster mitigation.

长期以来，川滇地区受到印度板块和欧亚板块碰撞的深刻影响，构造活动强烈，是研究陆-陆碰撞引起造山运动的天然实验场。然而，该区地质构造背景独特而复杂，对其地球动力学过程的认识一直存在争议，主要有刚性块体挤出，连续变形和中下地壳流等几种模式。其关键原因在于，受分辨率的限制，现有的研究成果没有全面刻画出大陆碰撞过程中岩石圈（尤其是中下地壳）的结构与物质组成。本研究拟利用“中国地震科学台阵”一期数据，结合川滇地区的固定地震台站数据，开展接收函数、瑞利面波频散和ZH振幅比的非线性联合反演研究，并考虑沉积盆地浅表地质结构对深部结构成像的影响，开展消除接收函数沉积效应等较为有实际意义的工作。在此基础上获取3维速度模型和地壳厚度、泊松比等地壳深部重要信息，重建川滇地区地壳精细结构，进一步研究地壳构造变形特征。旨在一方面为大陆动力学和地震孕育深部环境研究提供可靠的地球物理证据，另一方面服务于防震减灾需求。

本研究采用“中国地震科学台阵”一期波形数据和1985至2015年间川滇地区的地震目录数据开展了地壳精细结构和地震活动性分析的研究工作。一方面，通过改进双层H-k地壳扫描方法，得到较精确的浅表速度结构与莫霍面约束，再通过接收函数和面波频散联合反演，获取较可靠的速度结构和泊松比等地壳深部重要信息，重建了川滇地区地壳精细结构，刻画出大陆碰撞过程中岩石圈（尤其是中下地壳）的结构与物质组成，提高了地震成像的分辨率，为探索地质构造复杂的川滇地区地球动力学过程提供重要依据，进一步揭示了其地壳构造变形特征，以更好甄别刚性块体挤出，连续变形和中下地壳流等几种动力模式机制作用。另一方面，川滇地区受到印度板块和欧亚板块碰撞的深刻影响，构造活动强烈，是研究大陆动力学和地震孕育深部环境的天然实验场，通过地震活动性的统计与时空分析，很好地揭示了一些地壳软弱物质分布与地震构造及地震孕育深部环境的相关联系，为防震减灾需求提供重要支持。