秦岭造山带和云贵高原东南缘地壳剪切波分裂

发布时间：2018-06-17 06:39

本文选题：鄂尔多斯地块 + 秦岭造山带　；参考：《中国地震局地震预测研究所》2015年硕士论文

【摘要】：地壳中大量充满流体的定向排列的微裂隙是地壳介质各向异性的主要原因。剪切波是研究地壳介质各向异性的有效手段,当剪切波穿过地壳各向异性介质时,会产生分裂现象,产生两个描述地震各向异性的重要参数,快剪切波偏振方向和慢剪切波时间延迟。快剪切波偏振方向与裂隙走向一致,与原地主压力应力方向一致。慢剪切波时间延迟与介质的各向异性程度有关。地壳介质各向异性与区域构造密切相关,通过剪切波分裂参数可以探讨区域应力与构造的关系以及区域构造的复杂程度。秦岭造山带是华北板块和扬子板块的分界线,受到六盘山断裂、汾渭断裂带、龙门山断裂带等构造共同影响。本文运用SAM软件分析了陕西区域数字地震台网2006年1月-2014年3月的数字地震波形,获得了区域内17个台站的快波偏振方向和慢剪切波时间延迟。结果显示,快剪切波表现出了明显的分区特征。鄂尔多斯地块及渭河盆地东部台站表现出NE-SW和ENE-WSW向的快波优势偏振,与华北地区构造应力场一致;鄂尔多斯地块及渭河盆地西部台站,处于NW和NE向断裂的交汇处,快剪切波偏振方向较为复杂,反应出局部构造的复杂性。南秦岭以勉略缝合带为界,北部的秦岭微板块地区台站快剪切波偏振方向为NW-SE向和WNW-ESE向,与华南地区应力场方向一致;扬子板块北缘地区台站表现出NE-SW向的快波优势偏振方向,龙门山东北段延伸至此,区域断裂主要为NE向,表明该区快波偏振方向与区域断裂走向方向一致。研究区时间延迟结果表明,扬子板块北缘地区的时间延迟较为一致,大于其他区域的时间延迟,反映出区域各向异性程度较强。云贵高原东南部处于中国大陆东部与西部不同构造的转折区域。本文研究了贵州西南部和广西西北部地区流动台站的近震波形资料,SAM分析结果表明:区域快波偏振方向表现出较为明显的分区特征,贵州西南地区位于扬子板块和华南褶皱系右江褶皱带的过渡带,其快剪切波优势偏振方向近NE-SW,广西西北部位于华南褶皱系右江褶皱带,其快剪切波优势偏振方向为NW-SE方向,与华南地块主压应力方向一致。通过将区域慢剪切波时间延迟与川滇地块及华夏地块对比,得到该区地壳各向异性程度更接近于华南地块。
[Abstract]:The anisotropy of crustal media is mainly caused by a large number of directional microcracks filled with fluid in the crust. Shear wave is an effective method to study anisotropy of crustal medium. When shear wave passes through anisotropic medium of crust, it will split and produce two important parameters to describe seismic anisotropy. Polarization direction of fast shear wave and time delay of slow shear wave. The polarization direction of the fast shear wave is consistent with the fracture strike and the pressure stress direction of the original landlord. The time delay of slow shear wave is related to the anisotropy of the medium. The anisotropy of crustal media is closely related to regional tectonics. The relationship between regional stress and structure and the complexity of regional structures can be discussed by shear wave splitting parameters. Qinling orogenic belt is the dividing line between North China plate and Yangtze plate, which is influenced by Liupanshan fault, Fenwei fault zone and Longmenshan fault zone. In this paper, the digital seismic waveforms of Shaanxi regional digital seismic network from January 2006 to March 2014 are analyzed by using SAM software. The polarization direction of fast wave and the time delay of slow shear wave are obtained from 17 stations in the region. The results show that the fast shear wave shows obvious zonal characteristics. The fast wave dominant polarization of NE-SW and ENE-WSW in the eastern station of the Ordos block and Weihe basin is consistent with the tectonic stress field in North China, and the station in the west of the Ordos block and Weihe basin is located at the junction of NW and NE trending faults. The polarization direction of fast shear wave is complex, which reflects the complexity of local structure. The southern Qinling Mountains are bounded by Mianluo suture zone, and the polarization direction of fast shear wave in the northern Qinling microplate area is NW-SE direction and WNW-ESE direction, which is consistent with the stress field direction of South China, and the station in the northern margin of Yangtze plate shows the dominant polarization direction of NE-SW direction. At this point, the regional faults are mainly NE-trending, indicating that the polarization direction of the fast wave is consistent with the strike direction of the regional faults. The results of time delay in the study area show that the time delay in the northern margin of Yangtze plate is more consistent than that in other regions, which indicates that the anisotropy of the region is stronger. The southeastern Yunnan-Guizhou Plateau is located in the transitional region of different structures in the eastern and western parts of the mainland of China. In this paper, the near seismic waveform data of mobile stations in southwest Guizhou and northwest Guangxi are studied. The results of SAM analysis show that the polarization direction of regional fast wave shows obvious regional characteristics. Southwest Guizhou is located in the transitional zone of the Yangtze plate and the Youjiang fold belt of the South China fold system. The dominant polarization direction of the fast shear wave is near NE-SW.The northwest of Guangxi lies in the Youjiang fold zone of the South China fold system, and the dominant polarization direction of the fast shear wave is NW-SE. It is consistent with the principal compressive stress direction of the South China block. By comparing the time delay of regional slow shear wave with that of Sichuan-Yunnan block and Huaxia block, the crustal anisotropy of this area is closer to that of South China block.
【学位授予单位】：中国地震局地震预测研究所
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315.31

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