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安宁河-则木河断裂带及周边地区Rayleigh波群速度背景噪声成像研究
谭夏露,房立华,王未来,吴建平
作者单位E-mail
谭夏露 中国地震局地球物理研究所, 北京市民族大学南路5号 100081  
房立华 中国地震局地球物理研究所, 北京市民族大学南路5号 100081;中国地震局地震观测与地球物理成像重点实验室, 北京 100081 flh@cea-igp.ac.cn 
王未来 中国地震局地球物理研究所, 北京市民族大学南路5号 100081  
吴建平 中国地震局地球物理研究所, 北京市民族大学南路5号 100081;中国地震局地震观测与地球物理成像重点实验室, 北京 100081  
摘要:
安宁河-则木河断裂带位于川滇地块、巴颜喀拉地块和华南地块的交接部位,是川滇菱形块体的东部重要边界。利用布设在安宁河-则木河断裂带周边区域的西昌台阵和川西台阵均历时两年、共187个宽频带地震台站的垂直分量的背景噪声数据,采用噪声层析成像方法获得了这一区域4~20s的Rayleigh波群速度分布图像。与前人研究相比,本文结果的横向分辨率有明显改进,在安宁河-则木河断裂带可达20km左右,在其它区域可以达到20~40km。成像结果表明,安宁河-则木河断裂地区上地壳的速度结构存在明显横向不均匀性,速度分布特征与地表地质构造基本一致,不同周期的速度分布变化较小。盐源盆地、西昌盆地和四川盆地西南缘表现为低速异常。九龙附近和南部的德昌-盐边-巧家附近表现为高速异常,分别与出露的花岗岩体和峨眉山玄武岩有关。在安宁河断裂南段和则木河断裂北段能观测到断裂两侧的速度存在明显差异,其余断裂带两侧的速度对比不明显。贡嘎山附近的中上地壳表现为明显的低速异常,其东侧和西南侧高速体的阻挡,以及鲜水河-安宁河断裂带走向的变化,在贡嘎山区形成一个挤压弯曲段,使得川滇菱形块体的东南向水平运动转换为垂直于断裂的挤压作用和垂直隆升,导致了贡嘎山的快速隆起。
关键词:  安宁河-则木河断裂  噪声成像  互相关  频散  速度结构
DOI:
分类号:P315
基金项目:国家自然科学基金项目(41774067)、中国地震局川滇国家地震监测预报实验场项目(2017CESE0101)共同资助
Rayleigh Wave Group Velocity Tomography with Ambient Noise in the Anninghe-Zemuhe Fault Zone and Its Surrounding Areas
Tan Xialu,Fang Lihua,Wang Weilai,Wu Jianping
Abstract:
The Anninghe-Zemuhe fault zone is located at the junction of the Sichuan-Yunnan block,the Bayan Har block and the Southern China block,and is an important eastern boundary of the Sichuan-Yunnan block. The Rayleigh wave group velocity maps of 4~20s in this area are obtained with ambient noise tomography method,using two years vertical component ambient noise data recorded by 187 broadband seismic stations around the Anninghe-Zemuhe fault zone. Compared with previous studies,the lateral resolution has been improved greatly in this paper. The resolution is about 20km in the central Anninghe-Zemuhe fault zone,and 20~40km in other regions. The imaging results show that the velocity structure of the middle-upper crust in the Anninghe-Zemuhe fault area has obvious lateral inhomogeneity. The velocity structure is basically consistent with the surface geological structure,and the velocity maps differ little at different periods. The Yanyuan Basin,the Xichang Basin and the southwest margin of the Sichuan Basin are characterized by low velocity anomalies. The high speed anomalies near Dechang-Yanbian-Qiaojia, near the southern part of Jiulong are related to the exposed granite bodies and the Emeishan basalt. In the southern segment of Anninghe fault and the northern segment of the Zemuhe fault zone,there are obvious velocity contrasts between the two sides of the fault. The middle and upper crust in the vicinity of the Gongga Mountain is characterized by obvious low velocity anomalies. The obstruction of the high speed bodies in the east and the southwest sides of the Gongga Mountain,and the changes in the strike of the Xianshuihe fault and Anninghe fault,form a compression bending section in this area,making the south-east horizontal movement of the Chuandian block transfer to compress effect perpendicular to the fracture and vertical deformation,resulting in rapid vertical uplift of the Gongga Mountain.
Key words:  Anninghe-Zemuhe fault  Ambient noise tomography  Cross correlation  Surface wave dispersion  Velocity structure