华南地块及其邻区Rayleigh波相速度层析成像研究

发布时间：2018-06-18 23:46

本文选题：华南地块 + 背景噪声　；参考：《中国科学:地球科学》2016年11期

【摘要】：基于华南地块及其邻区609个宽频带地震台站2010~2012年的垂直分量连续波形记录,通过波形互相关和叠加计算得到各台站对间的经验格林函数.采用时频分析法提取出大量高质量的Rayleigh波相速度频散曲线,并反演得到了研究区周期6~50s的Rayleigh波相速度分布图像.结果显示周期6~10s的相速度分布与地壳中上部地质特征一致性较好,区域内的主要盆地和一些小尺度地堑和盆地呈现低速异常,造山带和褶皱带则呈现高相速度分布特征;周期20~30s的相速度分布以太行山-武陵山重力梯度带和地壳厚度突变带为界,西部地区主要表现为低速异常,东部地区则整体表现为高速异常,其中秦岭-大别造山带以南的华南地块东部相对以北的华北地块东部而言具有相对更高的相速度,可能与中生代以来华北克拉通和华南地块的构造演化存在差异有关;周期40~50s的相速度分布主要与下地壳和上地幔速度结构的横向变化有关,青藏高原东部因地壳厚度较厚表现为显著的低速异常,华北平原东南部和华南沿海地区表现为相对的高低速相间分布,四川盆地、鄂尔多斯盆地南部表现为显著高速异常,体现这两个块体稳定的上地幔岩石圈特征.从不同周期的相速度分布来看,华南地块西边界南段在云南东部及附近地区,相速度分布与当前的块体边界划分不太相符,仍需要深入研究.四川盆地相速度随着周期的增加存在"整体低速-盆地中部向外渐变高速-整体高速"的分布特点,反映了该盆地中部结晶基底和上地幔的高速.位于华北地块的鄂尔多斯盆地南部中上地壳存在一定程度的非均匀性,下地壳-上地幔顶部可能存在高速异常体.秦岭-大别造山带中段和位于桂东南的广西加里东期花岗岩分布区域在一定的周期范围存在显著高速异常体,其形成机理有待进一步分析.
[Abstract]:Based on the vertical component continuous waveform records of 609 broadband seismic stations in the Southern China block and its adjacent area in 2010~2012, the empirical Green function of each station pair is obtained through the cross correlation and superposition calculation. A large number of high quality Rayleigh wave velocity dispersion curves are extracted by the time-frequency analysis method, and the period 6~5 of the study area is obtained. The Rayleigh wave velocity distribution image of 0s shows that the phase velocity distribution of the period 6~10s is in good agreement with the upper and middle geological features of the crust. The main basins and some small graben and basins in the region present low velocity anomalies, and the orogenic belts and fold belts are characterized by high phase velocity distribution, and the phase velocity distribution of periodic 20~30s is in Taihang Mountain - The Wuling mountain gravity gradient zone and the crustal thickness mutation zone are bounded. The western region is mainly characterized by low velocity anomaly and the eastern region is characterized by high velocity anomaly. In the eastern part of the Qinling Mountains Dabie orogenic belt, the eastern part of the Southern China massif is relatively higher than the northern part of the North China block, and may be associated with the North China carat since the Mesozoic. The tectonic evolution of the Southern China massif is related to the difference of tectonic evolution. The phase velocity distribution of the period 40~50s is mainly related to the lateral variation in the velocity structure of the lower crust and upper mantle. The east of the Qinghai Tibet Plateau shows a significant low velocity anomaly due to the thicker crustal thickness, and the relatively high and low velocity distribution in the southeast of the North China Plain and the coastal area along the Southern China. The Sichuan basin and the southern Ordos Basin are characterized by remarkable high velocity anomalies, reflecting the lithosphere characteristics of the upper mantle of the two blocks. From the phase velocity distribution of different cycles, the velocity distribution in the southern part of the west boundary of the Southern China massif is not quite consistent with the current block boundary in the eastern and nearby areas of Yunnan. The distribution of the phase velocity in the Sichuan basin, as the period increases, is characterized by the distribution of the "overall low speed - the middle part of the basin in high speed to the whole high speed", which reflects the high velocity of the central crystalline basement and upper mantle in the middle of the basin. The upper crust of the middle upper crust of the southern Ordos Basin, located in the North China block, has a certain degree of inhomogeneity and the top of the lower crust and upper mantle. The middle section of the Qinling Mountains Dabie orogenic belt and the Guangxi CALEDONIAN GRANITE distribution area in the southeast of Guangxi have significant abnormal bodies in a certain period range, the formation mechanism of which remains to be further analyzed.
【作者单位】：江西省地震局;大地测量与地球动力学国家重点实验室中国科学院测量与地球物理研究所;
【基金】：地震科技星火计划项目(编号:XH16023、XH12027) 国家自然科学优秀青年基金项目(批准号:41422401) 地震行业科研专项项目(编号:201508020-05)资助
【分类号】：P315

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