3D polarimetric GPR coherency attributes and full-waveform inversion of transmission data for characterizing fractured rock
3D polarimetric GPR coherency attributes and full-waveform inversion of transmission data for characterizing fractured rock
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DOI：
10.1190/1.3103253
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发表时间：
2009-04
期刊：
影响因子：
3.3
通讯作者：
D. Sassen;M. Everett
中科院分区：
文献类型：
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作者：
D. Sassen;M. Everett
探地雷达（GPR）可以检测和描述裂缝，以帮助我们表征裂缝岩层。裂缝通过相长干涉和相消干涉改变GPR信号的入射波形或波形，这取决于裂缝的孔径、填充和取向。由于探地雷达的电磁波是矢量的，因此具有强方向性的特征可以改变入射场的极化状态。探地雷达方法关注波形或极化的变化，可以改善岩体内裂缝的检测和识别。相干性是一种以子波形式描述不连续性的地震属性，本文提出了一种基于相干性的极化探地雷达算法。在计算相干性时，它使用时域散射矩阵的最大特征值。该算法对波形敏感，不受雷达天线极化的影响。极化相干性比标量相干性更好地消除极化对从用于水文实验的裂缝石灰岩地块收集的现场数据的影响。另一种方法，用于透射数据的时域全波形反演，基于薄层模型定量地确定裂缝孔径和填充物的EM性质。野外资料反演结果与反射资料反演结果吻合较好。这两种方法提供了更好的裂缝检测能力和定量信息的裂缝孔径，介电常数，和电导率的填充比传统的GPR成像和标量相干属性。
Ground-penetrating radar (GPR) can detect and describe fractures to help us characterize fractured rock formations. A fracture alters the incident waveform, or wave shape, of a GPR signal through constructive and destructive interference, depending on the aperture, fill, and orientation of the fracture. Because the electromagnetic (EM) waves of GPR are vectorial, features exhibiting strong directionality can change the state of polarization of the incident field. GPR methods that focus on changes in waveform or polarization can improve detection and discrimination of fractures within rock bodies. An algorithm based on coherency, a seismic attribute that delineates discontinuities in wavelet shape, is developed for polarimetric GPR. It uses the largest eigenvalue of the time-domain scattering matrix when calculating coherence. This algorithm is sensitive to wave shape and is unbiased by the polarization of GPR antennas. Polarimetric coherency works better than scalar coherency in removing the effects of polarization on field data collected from a fractured limestone plot used for hydrologic experimentation. Another method, for time-domain full-waveform inversion of transmission data, quantitatively determines fracture aperture and EM properties of fill, based on a thin-layer model. Inversion results from field data show consistency with the location of fractures from reflection data. These two methods offer better fracture-detection capability and quantitative information on fracture aperture, dielectric permittivity, and electrical conductivity of the fill than traditional GPR imaging and scalar-coherency attributes.