Attenuation-compensated reverse time migration of GPR data constrained by resistivity  

电阻率约束的GPR衰减补偿逆时偏移成像

作　　者：Wang Hong-Hua Xi Yu-He Lv Yu-Zeng Wang Yu-Cheng 王洪华;席宇何;吕玉增;王欲成(桂林理工大学,地球科学学院,桂林541004)

机构地区：[1]College of Earth Sciences,Guilin University of Technology,Guilin 541004,China

出　　处：《Applied Geophysics》2022年第4期563-571,604,605,共11页应用地球物理（英文版）

基　　金：supported by the National Natural Science Foundation of China (No.41604102);the Guangxi Natural Science Foundation project (No.2020GXNSFAA159121).

摘　　要：The high-frequency electromagnetic waves of ground-penetrating radar(GPR)attenuate severely when propagated in an underground attenuating medium owing to the influence of resistivity,which remarkably decreases the resolution of reverse time migration(RTM).As an effective high-resolution imaging method,attenuation-compensated RTM(ACRTM)can eff ectively compensate for the energy loss caused by the attenuation related to media absorption under the influence of resistivity.Therefore,constructing an accurate resistivity-media model to compensate for the attenuation of electromagnetic wave energy is crucial for realizing the ACRTM imaging of GPR data.This study proposes a resistivity-constrained ACRTM imaging method for the imaging of GPR data by adding high-density resistivity detection along the GPR survey line and combining it with its resistivity inversion profile.The proposed method uses the inversion result of apparent resistivity data as the GPR RTM-resistivity model for imposing resistivity constraints.Moreover,the hybrid method involving image minimum entropy and RTM is used to estimate the medium velocity at the diff raction position,and combined with the distribution characteristics of the reflection in the GPR profile,a highly accurate velocity model is built to improve the imaging resolution of the ACRTM.The accuracy and eff ectiveness of the proposed method are verified using the ACRTM test of the GPR simulated data of a typical attenuating media model.On this basis,the GPR and apparent resistivity data were observed on a field survey line,and use the GPR resistivity-constrained ACRTM method to image the observed data.A comparison of the proposed method with the conventional ACRTM method shows that the proposed method has better imaging depth,stronger energy,and higher resolution,and the obtained results are more conducive for subsequent data analysis and interpretation.探地雷达(GPR)高频电磁波在地下衰减介质中传播时受电阻率的影响,吸收衰减强烈,严重降低逆时偏移成像分辨率;衰减补偿逆时偏移可利用介质电阻率有效补偿由介质吸收衰减造成的电磁波场能量损失,是衰减介质高分辨率成像的一种有效方法。如何精确构建地下介质电阻率模型以补偿衰减的电磁波能量是GPR衰减补偿逆时偏移成像的关键。为此,本文通过增加高密度电法探测并结合电阻率反演剖面,提出了一种电阻率约束的GPR衰减补偿逆时偏移成像方法。该方法利用高密度视电阻率数据的反演剖面作为GPR逆时偏移的电阻率模型,以施加电阻率约束;此外图像最小熵法与逆时偏移相结合方法用于估计绕射波位置处的介质速度,并综合考虑GPR剖面的反射波分布特征构建较为精确的速度模型,以提高衰减补偿逆时偏移成像分辨率。一个典型衰减介质模型的GPR模拟数据的衰减补偿逆时偏移测试验证了该方法的正确性和有效性。在此基础上,在野外某测线上分别采集GPR数据和高密度视电阻率数据,并利用电阻率约束的GPR衰减补偿逆时偏移方法对实测数据成像。将该方法与常规衰减补偿逆时偏移结果进行对比分析,结果表明:电阻率约束的衰减补偿逆时偏移可更有效地提高成像深度,成像能量更强,分辨率更高,其结果更有利于后续的资料分析与解释。

关 键 词：Ground-penetrating Radar attenuation compensated reverse time migration resistivity constrained high-density resistivity method minimum entropy method 

分 类 号：P631.3[天文地球—地质矿产勘探]