复杂地电模型的探地雷达时域有限差分正演  

FDTD METHOD FORWARD SIMULATION OF THE COMPLEX GEOELECTRICITY GPR MODEL

作　　者：喻振华[1] 冯德山[1] 戴前伟[1] 何继善[1] 

机构地区：[1]中南大学信息物理工程学院,长沙410083

出　　处：《物探化探计算技术》2005年第4期279-283,共5页Computing Techniques For Geophysical and Geochemical Exploration

基　　金：国家自然科学基金资助(50099620-03-02)

摘　　要：目前探地雷达正演模拟,都是针对简单的层状模型、圆状空洞、正方形空洞等单一的规则模型,而对于地下弯曲的界面或“V”字形等复杂模型的正演,实现起来较为困难。然而,地下构造是复杂的,因此,对复杂地电模型的正演研究显得更为重要。这里以麦克斯韦两个旋度方程为基本出发点,运用K.S.Yee的空间网格模型理论和时域有限差分法的基本原理,推导出二维空间的探地雷达正演方程组,通过讨论数值频散关系及其产生原因,推导出符合探地雷达实际传播规律的理想频散关系。为解决正演模拟时截断边界处的超强反射,采用了Mur超吸收边界条件,并以自制的探地雷达正演模拟程序为依托,对两个复杂的探地雷达模型进行了正演模拟,得到了正演剖面图。从其后模拟实例中的两正演剖面图可以看出,边界截断处的干扰波被大大地减少,消除边界反射后的雷达剖面能更好地指导工作人员进行地质解释,从而达到了把雷达的正演研究深入到复杂地电模型中去的目的,使正演研究更符合实际的地质情况。he conventional GPR forward simulations mainly aim at the singular and regular models,such as sandwich model,round cavity,square cavity,and so on,which are comparably simple with less consideration of forward complex model of curl interface underground or 'v' shape,for it is difficult to realize.As the underground structure is complex,so that it is important to forward the complex geoelectricity model.This article deduces a GPR forward system of equation of two dimensional spaces,by taking two Maxwell's curl equations as basic departure point and making use of the principles of K.S.Yee's space grid model theory and the basic principle of the finite difference time domain method(FDTD).By analysing the numerical frequency dispersion relation and the producing reason, it is deduced the ideal frequency dispersion relationship to match to GPR actual dissemination regulation.The author adopts Mur super absorbed boundary condition to solve the super strong reflection on the interceptive boundary when there is the forward simulation.And the author also conducted the forward simulation to two typical geoelectricity model by writing source codes with satisfied results,which can guide the staff member to process geology interpretation better for the actual radar section and instruct the worker to improve the acquisition of the radar datar.

关 键 词：探地雷达 时域有限差分法 正演模拟 理想频散关系 

分 类 号：P631.4[天文地球—地质矿产勘探]