重震联合反演青藏高原岩石圈密度结构  

Lithospheric density structure beneath the Tibetan Plateau from the joint inversion of gravity and seismic data

作　　者：宛家宽 罗志才 吴云龙 WAN JiaKuan;LUO ZhiCai;WU YunLong(National Gravitation Laboratory,Institute of Geophysics,MOE Key Laboratory of Fundamental Physical Quantities Measurement,School of Physics,Huazhong University of Science and Technology,Wuhan 430074,China;Wuhan Gravitation and Solid Earth Tides,National Observation and Research Station,Wuhan 430071,China;School of Geography and Information Engineering,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]国家精密重力测量科学中心,地球物理研究所,基本物理量测量教育部重点实验室,华中科技大学物理学院,武汉430074 [2]武汉引力与固体潮国家野外科学观测研究站,武汉430071 [3]中国地质大学(武汉)地理与信息工程学院,武汉430074

出　　处：《地球物理学报》2025年第2期470-482,共13页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41931074,41974096);武汉引力与固体潮国家野外科学观测研究站开放研究基金资助课题(WHYWZ202205)资助

摘　　要：本文联合重力和面波相速度数据反演了青藏高原岩石圈的密度模型,揭示了密度异常分布特征,并对密度异常的成因进行了讨论.模拟实验结果表明,面波相速度反演结果的横向分辨率在青藏高原东部达到1°,中部达到1.5°,西部低于2°,而重震联合反演结果的分辨率在青藏高原中西部均能达到1°;在波速异常和密度异常特征存在显著差异的情况下,重震联合反演的结果比面波相速度单独反演的结果更接近真实的密度模型.基于重震联合反演揭示的密度模型表明:(1)青藏高原中下地壳呈现显著的低密度、低VS异常,表明发生了部分熔融且存在地壳流通道.(2)青藏高原岩石圈地幔整体呈现高密度、低VS异常,表明上地幔可能发生了部分熔融和底侵作用.(3)班公湖—怒江缝合带和龙木错—双湖缝合带的岩石圈地幔呈现低密度、低VS异常,这可能是岩石圈地幔中橄榄岩的水合作用造成的;昆仑断裂带的低密度、低VS异常则支持该区域软流圈上涌的构造学说.(4)云贵高原、四川盆地和鄂尔多斯地体的岩石圈地幔呈现低密度、高VS异常,符合克拉通型岩石圈地幔特征.Using the joint inversion of gravity and surface wave phase velocity data,we developed the lithospheric density structure beneath the Tibetan Plateau and revealed the characteristics of the distribution of density anomalies.Then,we discussed the possible causes of the density anomalies.The results of simulation tests show that the lateral resolution of the inversion results of surface wave phase velocities reaches 1°in the eastern Tibetan Plateau,1.5°in the central Tibetan Plateau,and lower than 2°in the western Tibetan Plateau.And the model from the joint inversion of gravity and seismic data has resolution of 1°in both central and western Tibetan Plateau.In the case of significant differences between seismic wave velocity anomaly and density anomaly features,the results of the joint inversion of gravity and seismic data are closer to the real density structure than the results of the surface wave phase velocity inversion alone.The density model revealed by the joint inversion of gravity and seismic data shows that:(1)The middle and lower crust of the Tibetan Plateau shows remarkable low-density and low-VS anomalies,which indicate the possibility of crustal partial melting and the existence of the crust flow.(2)The lithospheric mantle beneath the Tibetan Plateau shows high-density and low-VS anomalies,which indicate the partial melting and underplating of the upper mantle.(3)The lithospheric mantle of the Bangonghu-Nujiang Suture and the Longmucuo-Shuanghu Suture exhibits low-density and low-VS features,which may be caused by the hydration of peridotite in the lithospheric mantle;the low-density and low-VS anomalies of the Kunlun Fault Belt support the tectonic theory of upwelling of the asthenosphere in this region.(4)Low-density and high-VS anomalies are found in the lithospheric mantle beneath Yunnan-Guizhou Plateau,Sichuan Basin and Ordos Block,which are consistent with the characteristics of craton lithospheric mantle.

关 键 词：青藏高原 岩石圈结构 密度模型 重震联合反演 

分 类 号：P312[天文地球—固体地球物理学] P315[天文地球—地球物理学]