3D prestack reverse time migration of ground penetrating radar data based on the normalized correlation imaging condition  

基于归一化互相关成像条件的三维GPR叠前逆时偏移成像

作　　者：Wang Hong-Hua Gong Jun-bo Zhang Zhi Xiong Bin Lv Yu-zeng Feng De-shan Dai Qian-wei 王洪华;龚俊波;张智;熊彬;吕玉增;冯德山;戴前伟(桂林理工大学,地球科学学院,桂林541004;广西隐伏金属矿产勘查重点实验室,桂林541004;中南大学,地球科学与信息物理学院,长沙410083)

机构地区：[1]College of Earth Sciences,Guilin University of Technology,Guilin 541004,China [2]Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin 541004,China [3]School of Geosciences and Info-Physics,Central South University,Changsha 410083,China.

出　　处：《Applied Geophysics》2020年第5期709-718,901,共11页应用地球物理（英文版）

基　　金：This work is supported by the National Natural Science Foundation of China(No.41604039,41604102,41764005,41574078);Guangxi Natural Science Foundation project(No.2020GXNSFAA159121,2016GXNSFBA380215).

摘　　要：The reverse time migration(RTM)of ground penetrating radar(GPR)is usually implemented in its two-dimensional(2D)form,due to huge computational cost.However,2D RTM algorithm is difficult to focus the scattering signal and produce a high precision subsurface image when the object is buried in a complicated subsurface environment.To better handle the multi-off set GPR data,we propose a three-dimensional(3D)prestack RTM algorithm.The high-order fi nite diff erence time domian(FDTD)method,with the accuracy of eighth-order in space and second-order in time,is applied to simulate the forward and backward extrapolation electromagnetic fi elds.In addition,we use the normalized correlation imaging condition to obtain pre-stack RTM result and the Laplace fi lter to suppress the low frequency noise generated during the correlation process.The numerical test of 3D simulated GPR data demonstrated that 3D RTM image shows excellent coincidence with the true model.Compared with 2D RTM image,the 3D RTM image can more clearly and accurately refl ect the 3D spatial distribution of the target,and the resolution of the imaging results is far better.Furthermore,the application of observed GPR data further validates the eff ectiveness of the proposed 3D GPR RTM algorithm,and its fi nal image can more reliably guide the subsequent interpretation.探地雷达(GPR)逆时偏移能够实现绕射波归位和能量收敛,但在处理三维介质时,二维逆时偏移难以实现绕射波的准确归位和能量的完全收敛。为此,本文提出了一种适合多偏移距GPR数据的三维叠前逆时偏移成像算法。其中,空间8阶和时间2阶精度的高阶FDTD正演算法用于计算源点正传和接收点反传电磁波场,以提高GPR逆时偏移的计算精度;归一化互相关成像条件用于获取叠前逆时偏移剖面;拉普拉斯滤波用于压制互相关计算过程中产生的低频噪声。数值试验结果表明:三维逆时偏移可获得与真实模型相吻合的成像剖面;与二维逆时偏移剖面相比,三维GPR逆时偏移剖面能更清晰、准确地反映目标体的三维空间分布形态,成像结果的分辨率更好。实测GPR资料的应用进一步验证了本文提出的三维GPR叠前逆时偏移算法的有效性,其结果可更可靠地指导实测资料的解释。

关 键 词：Ground Penetrating Radar(GPR) 3D Reverse Time Migration(RTM) Finite Diff erence Time Domain(FDTD) Normalized correlation imaging condition 

分 类 号：P631.3[天文地球—地质矿产勘探]