【作者】 吕子强；

【导师】 肖兰喜；

【作者基本信息】 中国地震局兰州地震研究所 ， 固体地球物理， 2009， 硕士

【摘要】 地球内部结构的研究一直都是地球物理学发展长河中的一个极为重要的基础科学领域。地震层析成像是反映地球内部构造的一种有效手段,通过地震层析成像技术的发展和有效利用,人们对地球内部结构有了更深一步的了解,对以后的科学发展和生态资源利用都起到了积极的推动作用。本文回顾了层析成像和地球物理反演的发展历史,阐述了层析成像和地球物理反演的国内外发展现状,特别是对初至波地震层析成像技术进行了研究。初至波是最先到达台站最容易辨认的波形。初至波成像可以减少由于波形的判断和读取精度所带来的误差,已经得到了越来越到人的接受和认可。本文以Asakawa的基于线性插值的射线追踪方法为出发点,对其进行了改进和拓展。对于二维初至波射线追踪方法,采用牛顿插值法替换原来的线性插值。从数值模拟计算的结果可知,精度显著提高,并保留了原有算法中对多种波形有效追踪的优点,层析成像的效果和精度得到了提高。对于三维初至波射线追踪方法,通过对接收点函数线性插值的二元偏导数计算得到射线与网格边界面的交点位置和接收点的走时时刻,并且沿用向前—向后的处理过程得到所有网格节点的走时时刻和任意位置的射线路径。通过数值模拟计算的结果可以看出,该算法的精度随着网格边界面划分的增加而提高,并且满足费马定理,同时从反演的结果可以看出,该算法对于水平块状模型的反演效果明显,并且适合速度突变的情况。应用三维初至波射线追踪方法对濮阳地震集中区进行地震层析成像研究分析。从反演的速度结构切面得知,以聊城—兰考断裂为界的东西部高低速度异常比较明显,主要表现为以凹陷构造为主的地区呈现为低波速异常,以隆起构造为主的地区呈现为高波速异常。该区地震集中发生主要是因为鲁西隆起和东濮凹陷之间的断层的相互作用和应力调整的结果,而对于震源极浅、震源集中及错动方式一致的地震,油田注水可能起到了一定的诱发作用。另外,发现鲁西隆起的相对速度异常程度高于内黄隆起的相对速度异常,这也可能与地震集中在东濮凹陷东侧有一定的联系。这些对该区未来的异常趋势的判断和研究起到了一定的促进作用。更多还原

【Abstract】 The research of the internal structure of the Earth has always been a very important basic science in the development of the long river of Geophysics. Seismic tomography is an effective means that can reflect the internal structure of the Earth. Through the development and effective use of seismic tomography technology, the internal structure of the Earth has been a deeper understanding by people, and the future scientific research and the use of ecological resources has been enhanced profitably.This paper reviews the history of the tomography and geophysical inversion, and described the current development of tomography and geophysical inversion at all over the world, especially for first-arrival wave seismic tomography.First-arrival wave is the first acceptable waveform by station, First-arrival wave tomography can reduced the precision errors because of the judge for waveform and reading for arrive times, has been accepted and licensed by more and more people. In this paper, the Asakawa method-based linear travel-time interpolation method of the ray tracing has been improved and expanded. For the first-arrival wave two-dimensional ray-tracing method, Newton travel-time interpolation method replaces the original linear travel-time interpolation. From the numerical simulation calculated results, it’s obviously found that the accuracy can be significantly improved and the advantages of the original algorithm that can trace multi-wave also be retained, and the effectiveness and accuracy of tomography has been enhanced better. For the first-arrival wave three-dimensional ray-tracing method, through linear travel-time interpolation to grid border and partial derivative calculation, the location and travel-time of the intersection point can be confirmed. Through go on using forward-backward ray-tracing process, all the grid nodes travel-time and any place ray path can be calculated. From the numerical simulation calculated results, it’s obviously found that the accuracy of the algorithm increases with the surface mesh subdivision, and the method meets the Fermat theorem. At the same time from the inversion results can find that the algorithm fit the horizontal block model and the condition of speed abnormity.Make use of three-dimensional ray-tracing method to seismic tomography and seismic tomography; first-arrival wave; velocity structure; the earthquakes concentrated region更多还原