融合衰减补偿与多次波压制的水域探地雷达逆时偏移成像

It is very difficult to overcome the shortcomings and limitations in the traditional acoustic or non-acoustic exploration methods for underwater stratigraphic structure and buried body. And the absorption of the underwater strata, the multiples and the diffraction of the underwater interface are also causing serious problems to GPR detection in water area. A significant breakthrough of underwater GPR detection must be achieved through the study of key scientific issues. Based on the improved generalized S-transform, the attenuation compensation method suitable for the propagation of electromagnetic waves in the loss medium is explored by using the attenuation compensation technique in the seismic data processing. Next, by researching generating mechanism and signatures of GPR multiples, we try and give the best combination scheme including predictive deconvolution, surface-related multiple elimination and Radon transform according to kinematics and dynamics features of GPR multiples. Finally, on the basis of above-mentioned, the impact of media dispersion and electromagnetic wave attenuation are considered to migration imaging. GPR wave field continuation operator will be constructed from the Maxwell equations including conduction current, and algorithms of reverse-time migration will be optimized so as to develop a GPR reverse-time migration technology combined attenuation compensation and multiples suppression in water area and realize the goal of accurately detecting underwater stratigraphic texture and buried bodies.

水底地层结构和掩埋体探测的传统声波抑或是非声波类方法，存在着几近难以克服的缺憾，而水底地层的吸收、水底界面多次波以及水底起伏界面的绕射等因素又对水域探地雷达技术产生严重困扰。因此，必须通过关键科学问题的研究取得水下探测的突破性技术创新。本项目拟通过水域探地雷达数值模拟分析，借鉴地震数据中的衰减补偿技术，基于改进的广义S变换，探索适于有耗介质电磁波传播的衰减补偿方法；通过研究水域雷达探测的多次波产生机理和特征，综合依据多次波的运动学和动力学特征，开展包括预测反褶积、SRME、Radon变换等多次波压制方法的优化组合研究。在前述基础上，考虑介质频散和衰减对偏移成像效果的影响；并从考虑传导电流项的麦克斯韦方程组出发，构建电磁波场外推算子，对逆时偏移算法进行优化；最终形成融合衰减补偿与多次波压制的水域探地雷达逆时偏移成像技术，实现能准确探测水底地层结构和掩埋体的根本目标。

在水域工程（如海堤、水库、桥梁、航道和港口等）以及水下考古领域，经常需要对水域地层结构进行详细调查以及对水下掩埋体进行快速准确的探测。水域探测试验表明，探地雷达作为一种快速、经济和可靠的地球物理探测方法，可以对水下的地层结构和掩埋体进行高质量成像。而水底地层的吸收、水底界面多次波以及水底起伏界面的绕射等因素又对水域探地雷达技术产生严重困扰。通过基于广义S变换实现水域雷达探测水底地层的高频衰减补偿、基于局部频率域SVD的杂波和随机噪声压制和多频数据融合，提升水域雷达探测数据质量；在预测反褶积与SRME方法优化的基础上，形成优化的多次波组合压制策略。采用改进后的质心频率下降法对水底地层衰减系数进行准确估计，实现考虑水底地层衰减补偿的逆时偏移成像，最终形成了一套完整的水域探地雷达逆时偏移成像技术体系。研究成果可为水域探测提供强大的技术支撑，从而促进水利工程隐患排查、桥梁和航港工程病害检测以及沉船探寻和救捞、水下遗址遗迹调查考古等事业的发展。