利用背景噪声层析成像反演华南地区S波速度结构

发布时间：2018-11-28 14:17

【摘要】：研究区位于中国大陆的南部(99°E-122°E,18°N-33°N),受印度洋板块、菲律宾海板块和西太平洋板块向欧亚板块俯冲的共同作用,研究区构造格局复杂,构建壳幔速度模型对于了解该区构造演化特征具有重要意义。但研究区内地震活动性差异巨大,传统的基于地震的层析成像方法难以获得整个研究区的地壳结构,本文用近年来新发展的背景噪声成像方法反演了华南地区高精度的地壳S波速度结构。本研究收集了华南地区国家台网和14个省(安徽、重庆、福建、广东、广西、贵州、湖北、海南、湖南、江西、四川、西藏、云南、浙江)区域台网共计244个宽频带地震台站记录的2013年1月到2013年12月的垂直分量连续波形资料,首先通过单台数据预处理、互相关计算与叠加、群速度频散测量和质量评估等处理获得了不同周期的瑞利波群速度频散曲线,然后用Torantola非线性反演得到该区8-35s的瑞利波群速度分布,最后由纯路径频散反演获得研究区0-60km深度范围内的S波速度结构。结果表明:(1)在浅层地壳,受地表地形影响,四川盆地和江汉盆地表现为低速异常,华南褶皱带表现为高速异常,随深度增加,盆地区由沉积层引起的低速异常逐渐降低;(2)研究区自西向东,地壳厚度存在非均匀减薄,而东扬子克拉通和华南褶皱带的地壳厚度变化不大;(3)四川盆地北部浅部地壳的显著低速异常,表明该区存在比盆地其他区域更厚的沉积层(约10km以上),四川盆地中央在约10-15km深度范围内存在的高速异常,可能反映出盆地中央的基地上隆特征;(4)川滇地块从地表到中下地壳总体上表现为低速异常,这可能与川滇地块地壳中存在的高热流值有关。而在川滇地块南部和扬子克拉通西部的交界地带出现的明显低速异常可能与青藏高原物质东流有关。
[Abstract]:The study area is located in the southern part of the Chinese mainland (99 掳E-122 掳EN 18 掳N-33 掳N), is subjected to the combined action of the Indian Ocean Plate, the Philippine Sea Plate and the Western Pacific Plate subducting to the Eurasian Plate, and the tectonic framework of the study area is complex. The establishment of crust-mantle velocity model is of great significance for understanding the characteristics of tectonic evolution in this area. However, there are great differences in seismicity in the study area, so it is difficult for the traditional seismic tomography method to obtain the crustal structure of the whole study area. In this paper, the highly accurate crustal S wave velocity structure in South China is inversed by using the background noise imaging method which has been developed in recent years. In this study, the National Taiwan Network of South China and 14 provinces (Anhui, Chongqing, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hainan, Hunan, Jiangxi, Sichuan, Tibet, Yunnan) were collected. Zhejiang) regional network recorded a total of 244 broadband seismic stations from January 2013 to December 2013 vertical component continuous waveform data, first through a single data preprocessing, cross-correlation calculation and superposition, The dispersion curves of Rayleigh wave group velocities with different periods are obtained by group velocity dispersion measurement and quality evaluation, and the Rayleigh wave group velocity distributions of 8-35s in this area are obtained by Torantola nonlinear inversion. Finally, the S-wave velocity structure in the depth range of 0-60km is obtained by pure path dispersion inversion. The results are as follows: (1) in the shallow crust, influenced by the surface topography, the Sichuan and Jianghan basins exhibit low velocity anomalies, while the South China fold belt shows high speed anomalies. With the increase of depth, the low velocity anomalies caused by sedimentary layers in the basin area decrease gradually; (2) from west to east, the thickness of the crust decreases inhomogeneously, but the thickness of the crust in the eastern Yangtze craton and the southern China fold belt has little change; (3) the obvious low-velocity anomalies of the shallow crust in the northern part of the Sichuan Basin indicate that there are thicker sedimentary layers (about 10km) in this area than in other regions of the basin, and the high-speed anomalies in the center of the Sichuan Basin in the range of about 10-15km depth. It may reflect the characteristics of base uplift in the center of the basin. (4) the Sichuan-Yunnan block shows a low velocity anomaly from the surface to the middle and lower crust, which may be related to the existence of high heat flow in the crust of the Sichuan-Yunnan block. The apparent low velocity anomaly in the southern part of the Sichuan-Yunnan block and the western Yangtze craton may be related to the eastward flow of matter in the Qinghai-Tibet Plateau.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315.2

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