地质雷达有限差分逆时偏移方法研究

发布时间：2018-07-05 04:58

本文选题：地质雷达 + 有限差分　；参考：《地球物理学进展》2017年02期

【摘要】：地质雷达技术是用于研究水文、环境与气候变化等重大科学问题最有效的地球物理技术之一,并广泛应用于检测道路和建筑内部结构,探测冻土层、沙漠沙丘演化特征,进行地质灾害和考古探测等.具有探测速度快、分辨率高和探测结果直观成像的优势.但由于受到介质横向速度变化,孤立块体的绕射波和倾斜界面复杂反射波的影响等,在雷达探测剖面上经常难以真实地反映地下目标体的空间位置和形态.偏移处理技术可以提高成像的真实性.逆时偏移能有效地利用回转波、多次波成像,使反射波准确归位,绕射波完全收敛,是一种受横向变化影响小,倾斜界面成像精度高的偏移方法.本文推导出基于麦克斯韦方程组TM波方程的有限差分格式、稳定性条件和PML边界条件,并编程实现有限差分零偏移距逆时偏移算法.两层模型和空洞模型的逆时偏移剖面与对应的原速度模型完全相同,有效地验证了有限差分零偏移距逆时偏移算法的准确性.相比于两层模型和空洞模型的Kirchhoff偏移剖面,逆时偏移剖面能更有效地提高垂直界面和空洞底界面的成像分辨率,更真实地反映两层模型和空洞模型的空间形态和内部结构信息.
[Abstract]:GPR technology is one of the most effective geophysical techniques used to study the major scientific problems such as hydrology, environment and climate change, and is widely used to detect the internal structure of roads and buildings, and to detect the evolution characteristics of frozen soil and desert dunes. Carry out geological disasters and archaeological exploration, etc. It has the advantages of high detection speed, high resolution and visual imaging. However, due to the influence of the lateral velocity of the medium, the diffraction wave of isolated block and the complex reflection wave of inclined interface, it is often difficult to truly reflect the spatial position and shape of the underground object in the radar detection profile. Migration processing technology can improve the authenticity of imaging. Inverse time migration can make use of rotation wave and multiple wave imaging effectively, so that the reflected wave can be accurately located and the diffraction wave converges completely. It is a migration method with little influence on lateral change and high imaging accuracy at inclined interface. In this paper, the finite difference scheme, stability condition and PML boundary condition of TM wave equation based on Maxwell equations are derived, and the inverse time migration algorithm of finite difference zero offset is realized by programming. The inverse time migration profile of the two-layer model and the cavity model are exactly the same as the corresponding original velocity model, which effectively verifies the accuracy of the finite difference zero offset inverse time migration algorithm. Compared with Kirchhoff migration profile of two-layer model and voids model, inverse time migration profile can improve the imaging resolution of vertical interface and cavity bottom interface more effectively, and more truly reflect the spatial shape and internal structure information of two-layer model and voids model.
【作者单位】：中国地质大学(北京) "地下信息探测技术与仪器"教育部重点实验室;
【基金】：国家重点基金委项目(2145803) 教育部基科研费优秀教师基本项目(53200859531)联合资助
【分类号】：P631.3

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