华南北部背景噪声层析成像

发布时间：2018-06-25 07:11

本文选题：互相关 + 背景噪声　；参考：《地球物理学进展》2017年04期

【摘要】：本文研究区域位于华南大陆北缘与华北克拉通交界处(112°E~119°E,29°N~33°N),主要包含了秦岭-大别造山带、苏北盆地南缘、江汉盆地以及扬子准克拉通部分地区.本次研究利用北京大学以及南京大学安装的共计60台流动地震台站从2014年9月开始记录的连续地震波形数据,通过背景噪声互相关方法获得研究区域经验格林函数并提取频散曲线.本文先使用了线性叠加以及S-transform方法提高互相关函数的信噪比,并同时使用FTAN方法以及一种谱方法来提取瑞利波相速度频散曲线,为了对频散曲线进行质量控制,本文还使用了一种基于机器学习的k近邻算法来自动识别过滤异常频散曲线.最终利用频散信息进行层析成像,获得了研究区域8~35 s的瑞利波相速度分布图.结果表明:(1)谱方法提取的频散曲线与FTAN方法获得的结果相一致,且能够克服3倍波长的限制,对于研究区域较小具有重要意义.(2)8 s周期速度异常显示江汉盆地沉积中心位于30°~30.5°范围内,且呈NW向展布;(3)12~14 s的速度异常暗示江汉盆地的基底大约是15 km,这与其地震活动性一致;(4)20 s周期的高速异常显示江汉盆地具有较浅的莫霍面,而苏北盆地南缘以及黄山地区可能具有较深的莫霍面.(5)苏北盆地南缘8~35 s周期均呈现低速异常,这可能说明其具有巨厚的沉积层以及较深的莫霍面.
[Abstract]:The study area is located at the junction of the northern margin of the South China continent and the North China Craton (112 掳E ~ (119) 掳E ~ (29) 掳N ~ (33 掳N) and mainly includes the Qinling Dabie orogenic belt, the southern margin of the Subei Basin, the Jianghan Basin and some areas of the Yangtze quasi craton. This study uses a total of 60 mobile seismic stations installed by Peking University and Nanjing University to record continuous seismic waveform data from September 2014. The empirical Green's function of the studied region is obtained by the background noise cross-correlation method and the dispersion curve is extracted. In this paper, the linear superposition method and S-transform method are used to improve the signal-to-noise ratio of the cross-correlation function. FTAN method and a spectral method are used to extract the Rayleigh wave phase velocity dispersion curve in order to control the quality of the dispersion curve. This paper also uses a k-nearest neighbor algorithm based on machine learning to automatically identify filtered anomalous dispersion curves. Finally, the Rayleigh wave phase velocity distribution map of the study area of 8 ~ 35 s was obtained by using dispersive information. The results show that: (1) the dispersion curves extracted by the spectral method are consistent with those obtained by the FTAN method and can overcome the limitation of 3 times wavelength. It is important for the study area to be small. (2) the 8 s periodic velocity anomaly shows that the sedimentary center of Jianghan Basin is located in the range of 30 掳~ 30.5 掳. (3) the velocity anomaly of 12 ~ 14 s implies that the basement of Jianghan basin is about 15 km, which is consistent with the seismicity of Jianghan basin, and (4) the high speed anomaly of 20 s period shows that Jianghan basin has a shallow Moho surface. However, the southern margin of Subei basin and Huangshan area may have deeper Moho surface. (5) the 835 s cycle of the southern margin of Subei basin shows a low velocity anomaly, which may indicate that it has a very thick sedimentary layer and a deeper Moho surface.
【作者单位】：北京大学地球与空间科学学院地球物理研究所;
【分类号】：P315.7

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