三维探地雷达数值模拟中UPML边界研究

应用时域有限差分进行探地雷达正演计算时,边界条件的吸收效果是提高雷达波响应模拟精度的关键因素之一。这里推导出了三维各向异性完全匹配空间UPML吸收边界的计算公式,并编程实现。模拟结果表明:UPML吸收边界在吸收效果,反射误差及计算效率等方面,都明显优于常用的Mur、PML吸收边界,具有较好的模拟效果。采用三维UPML边界的时域有限差法,可以提高探地雷达正演模拟的可靠性、准确度。     

新的机遇,新的挑战--关于"十五"工作的设想

地震科学经历近百年的发展,现已步入中年.文章介绍针对地震科学当前面临的主要问题,IASPEI采取的措施和努力的方向,其中强调了宽频带数字地震观测在地震研究中的作用.这些背景值得我们在编制"十五"规划时借鉴.     

青藏高原东部及邻区宽频地震观测初报

利用宽频带数字地震仪在川西高原、云贵高原西部开展了为期一年的地震观测,记录了许多地震波形数据,并对川青地块、川滇地块和华南地块上的5个台站的不同地震纪录进行了频谱试分析。     

3D GPR measurements for archaeological application with interpretation aided by numerical modelling

The paper presents the results of georadar investigations carried out in the area of the monastery at Tyniec near Cracow for archaeological purposes. The georadar profiles were designed on the abbey courtyard in a regular grid, which covered the area of the buildings that currently do not exist. The aim of the measurements was to produce a 3D visualization of former buildings’ foundation. The results of the geophysical measurements were correlated with the information obtained from archaeological investigations. The georadar surveys confirmed the location of foundations documented by archeologists and new underground structures were discovered. To aid the interpretation, numerical modelling of the electromagnetic wave field was performed. Computer modelling allowed to determine the kind and condition of underground structures.     

Magnetic and ground probing radar measurements for soil pollution mapping in the industrial area of Val Basento (Basilicata Region, Southern Italy): a case study

The joint application of electromagnetic techniques for near-surface exploration is a useful tool for soil pollution monitoring and can also contribute towards describing the spatial distribution of pollutants. The results of a geophysical field survey that was carried out for characterizing the heavy metal and waste disposal soil pollution phenomena in the industrial area of Val Basento (Basilicata region, Southern Italy) are presented here. First, topsoil magnetic susceptibility measurements have been carried out for defining the spatial distribution of superficial pollution phenomena in the investigated area. Second, detailed and integrated measurements based on a high-resolution magnetic mapping and ground probing radar (GPR) profiling have been applied to investigate the subsurface in two industrial areas located in more polluted sites that were identified during the first phase. Our monitoring strategy discloses the way to rapidly define the zone characterized by high pollution levels deriving from chemical industries and traffic emissions and to obtain the way information about the presence of local buried sources of contamination.     

钢筋混凝土GPR检测图像的目标体快速识别技术

在一般的城建工程结构体的探地雷达检测中,为减小检测工作周期,需要进行现场探测、处理及解释;或是检测工区数据量大,逐个剖面进行人工处理解释需要很大的工作量和工作时间。为解决这些问题,引入了基于F—K偏移及小波变换法图像分割的目标体快速识别技术,对钢筋混凝土探地雷达检测图像进行处理,达到了对钢筋混凝土结构探地雷达检测图像快速处理与解释的效果,也为能够把数据处理程序直接嵌入探地雷达系统中提供理论基础。     

探地雷达技术及其探测的应用

介绍探地雷达技术探测原理及方法特点,总结研究探地雷达可应用领域,通过部分工程实施给予论证。     

Nanosecond electromagnetic sounding of a fluid-saturated layered formation

Mathematical modeling was applied to study attenuation of a nanosecond pulse that propagated in an oil-bearing formation and was reflected from the oil-gas or oil-water interfaces. The problem was formulated and solved for propagation of a short electromagnetic Gaussian pulse in a layered hydrocarbon reservoir in the case of excitation by a long electric line. Complex permittivity of oil-bearing rocks was calculated using a refractive mixing dielectric model for oil, saline water, methane, quartz, and bentonite in each layer. We obtained and analyzed space-time diagrams of wave propagation and reflection and estimated effective attenuation for both cases.