探地雷达:浅表地球物理科学技术中的重要工具

探地雷达(GPR)是浅表地球物理科学技术中的一项重要手段.其重要性体现在它的应用广泛性和有效性.在工程检测、环境保护、文物考古、灾害救援、反恐安检、资源勘探、水文水利等科学技术领域中探地雷达都在发挥着其他手段无法取代的重要作用.关于探地雷达发展历史、基本系统及原理、信号处理与成像等方面的综述性文章已经很多.本文将重点评述作为浅表地球物理观测技术重要手段的探地雷达在几个基础地学与工程技术领域中的应用.这些方面包括沙漠中高大沙丘的内部结构与形成机理,永久冻土的现状探测与演化预测,民用基础设施(公路、桥梁、大坝、堤防)内部或地基内空洞及软弱带的检测,以及地震灾害现场生命探测与救援.本文还将用一定篇幅评述探地雷达技术的变异形式(如钻孔雷达、探月雷达).评述将结合观测实例,尤其是在中国大陆的实例.最后将就探地雷达技术现存的问题及发展方向提出个人见解.需要强调的是,尽管本文以探地雷达的科研应用为主题,浅表地球物理科技成果在各个领域的成功应用绝对不可能倚赖任何单一手段或方法.所有成功的实例都证明一定要强调某一方法为主,其他手段为辅,多手段、多方法的有效配合,才有可能最大程度的减小探测结果的非唯一性,提高准确度和精确度.

Ground Penetrating Radar:A critical tool in near-surface geophysics

Ground Penetrating Radar(GPR)is one of the most important techniques in near-surface geophysics. The importance of its critical role is best expressed by the wide breadth of its application in all disciplines of near-surface geophysics. In the disciplines such as groundwater hydrogeology, engineering non-destructive testing, contaminant migration monitoring, cultural heritage protection, life search and rescue at hazard sites, national security and counter-terrorism, as well as natural resource exploration, GPR is playing a critical role that is not easily replaceable by other observation techniques. This paper reviews a number of critical aspects in GPR applications in fundamental earth science and applied technologies. Associated with fundamental earth science we review the studies of the internal structure that is critical to the formation of high sand-dunes and desertification. GPR can sensitively respond to the variation of water contents inside a sand dune, and reveal the groundwater condition that critically controls the water supply in desert area. In permafrost detection, GPR is a powerful tool to delineate the interface of the active layer above the permafrost, and is able to image a variety of objects inside the frozen formation such as the ice lens, ice wedge, and boulders. Due to the scattering nature for all these kinds of individual targets, the success of the application of GPR research in permafrost science and engineering should be through broad-band, multi-offset, full three-dimensional data acquisition, analysis, and interpretation. Associated with engineering applications, we review GPR characterization of infrastructure health status in terms of the relativity of the anomaly size and GPR wavelength. We also review the topic of human vital sign detection for rescue, a research area generated much interest in near-surface geophysics community. For completeness of the review we also briefly discuss some techniques evolved based on GPR with the examples in borehole radar, and lunar penetrating radar(LPR). At the end of each section we provide our personal view on the existing problems and bottle-necks of the current status of GPR, and its possible direction for future development.#br#As geophysicists in general, we also want to remind the readers that even this paper is a review of GPR technique, it is always beneficial to remember that the success of near-surface geophysics, as both a scientific field and technical area, is heavily rely on the collaborative and smart use of multiple types of observation techniques to eliminate the non-uniqueness of geophysical detection as much as possible, to reach the ultimate goal to provide the best possible constraints in subsurface characterization and imaging.