地球物理学进展 ›› 2019, Vol. 34 ›› Issue (4): 1671-1678.doi: 10.6038/pg2019CC0139

• 应用地球物理学Ⅱ(海洋、工程、环境、仪器等) • 上一篇    下一篇

基于FDTD的探地雷达三维逆时偏移成像

王敏玲1,2,廖天元1,王洪华1,2,*(),张智1,2,熊彬1,2   

  1. 1. 桂林理工大学地球科学学院,广西桂林 541004
    2. 广西隐伏金属矿产勘查重点实验室,广西桂林 541004
  • 收稿日期:2018-09-30 修回日期:2019-05-20 出版日期:2019-08-20 发布日期:2019-08-30
  • 通讯作者: 王洪华 E-mail:wanghonghua5@163.com
  • 作者简介:王敏玲,女,1988年生,博士,讲师,主要从事地震波成像理论及应用研究. (E-mail: wangml@glut.edu.cn)
  • 基金资助:
    国家自然科学基金(41604102);国家自然科学基金(41604039);国家自然科学基金(41674075);广西自然科学基金(2016GXNSFBA380082);广西自然科学基金(2016GXNSFBA380215);广西自然科学基金(2016GXNSFGA380004);广西中青年教师基础能力提升项目(KY2016YB199)

3D reverse time migration of ground penetrating radar based on finite difference time domain method

WANG Min-ling1,2,LIAO Tian-yuan1,WANG Hong-hua1,2,*(),ZHANG Zhi1,2,XIONG Bin1,2   

  1. 1. College of Earth Sciences, Guilin University of Technology, Guangxi Guilin 541004, China
    2. Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guangxi Guilin 541004, China
  • Received:2018-09-30 Revised:2019-05-20 Online:2019-08-20 Published:2019-08-30
  • Contact: Hong-hua WANG E-mail:wanghonghua5@163.com

摘要:

探地雷达(GPR)二维逆时偏移算法在处理实际三维雷达资料时,难以实现绕射波的准确归位和能量的完全收敛,严重制约着地下三维目标体的成像精度.本文提出了一种基于时域有限差分法(FDTD)的GPR三维逆时偏移算法,其中基于单轴各向异性完全匹配层(UPML)的GPR三维FDTD算法用于计算三维电磁波场的正向和逆时延拓;基于爆炸反射面原理的零时刻成像条件用于获取三维GPR叠后逆时偏移成像剖面;拉普拉斯滤波用于压制低频噪声.将该算法应用于一个长方体空洞模型的三维正演数据中,通过对比逆时偏移前、后的雷达剖面和速度模型可知:GPR三维逆时偏移算法能使正演剖面中的反射波归位、绕射波收敛且逆时偏移剖面与对应的速度模型非常吻合,能够精确重构异常体的三维空间形态和内部结构信息,极大地提高了雷达剖面的分辨率.

关键词: 探地雷达, 三维逆时偏移, 零时刻成像条件, 时域有限差分法

Abstract:

Due to the huge computational cost, Reverse Time Migration (RTM)of Ground Penetrating Radar (GPR)is usually implemented in its two-dimensional (2D)form. However, a 2D RTM algorithm can hardly focus the scattering signal form objected buried in a complicated subsurface environment and produce a high-precision subsurface image for the actual three-dimensional (3D)geological structure. This paper proposes a 3D RTM algorithm for GPR based on the Finite Difference Time Domain (FDTD)method. The 3D FDTD algorithm with uniaxial anisotropic Perfectly Matched Layer is used in forward modelling and backward extrapolation of electromagnetic fields. The zero time imaging condition which based on the principle of explosive reflector, is used to yield the RTM results and a Laplace filter is used to suppress the low frequency clutter. The effectiveness of the proposed 3D RTM algorithm is demonstrated using a 3D numerical model with a subsurface cubic void. Applied the proposed algorithm to the 3D simulated data of a cubic void model, and the compared results of profiles of before and after the RTM process demonstrated that the GPR 3D RTM algorithm can make the diffracted wave converged into real location which is consistent with the real model. The 3D RTM algorithm can accurately reconstruct the 3D space of abnormal body shape and internal structure information, which greatly improved the resolution of the GPR profiles.

Key words: Ground Penetrating Radar (GPR), Three Dimensional Reverse Time Migration (3D-RTM), Zero Time Imaging Condition, Finite Difference Time Domain method(FDTD)

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