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1. 2D inversion of frequency-domain electromagnetic data generated by line current source | |||
TONG Xiaozhong,CAO Chuanghua,LIU Jianxin | |||
Earth Science 18 November 2015 | |||
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Abstract:The inversion of electromagnetic data is an inherently non-unique and unstable problem due to the data noises and incomplete data coverage, which means different geo-electrical models could fit the observed data at the same level. A stable solution of an ill-posed inverse problem can be obtained by the regularization methods in which some desired structure are imposed to stabilize the inverse problem. We have developed an algorithm to invert frequency-domain electromagnetic data generated by a line current source for a 2D model of the earth. To stabilize the inversion, we adopt a smoothness-constraint approach for the model parameters and adjust the regularization parameter objectively using a adaptive regularization parameter technique. For calculating the sensitivities using any of the accurate methods will be very time-consuming, we applied the adjoint-equation approximate method. By means of the numerical examples using synthetic data, we have demonstrated that the inversion method can be effectively to reconstruct the subsurface resistivity structure. | |||
TO cite this article:TONG Xiaozhong,CAO Chuanghua,LIU Jianxin. 2D inversion of frequency-domain electromagnetic data generated by line current source[OL].[18 November 2015] http://en.paper.edu.cn/en_releasepaper/content/4662949 |
2. Detection of LNAPL contamination with GPR and resistivity surveys | |||
LU Qi,LIU Cai,FENG Xuan,LI Hongli,LIANG Wenjing,ZOU Lilong | |||
Earth Science 25 November 2011 | |||
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Abstract:This paper presents the effectiveness of electromagnetic (EM) exploration techniques for detecting near-surface soil contaminants. Field work has been done at a former industrial site containing light non-aqueous phase liquid (LNAPL) in soils. The experiment shows that a combination of ground penetrating radar (GPR) and electrical resistivity can provide an effective means of mapping subsurface contamination. Soil cores sampled in the three boreholes clearly indicate that the concentration of total petroleum hydrocarbons (TPH) has an inverse relation to the relative dielectric constant and a direct proportional correlation with the electrical resistivity.GPR data have high spatial resolution and enable us to image the shallow subsurface stratigraphy, although its depth of penetration is greatly limited in a conductive region. The electrical resistivity method is effective to obtain the resistivity structure associated with the subsurface stratigraphy and the contamination zone. Three-dimensional GPR and resistivity images are constructed to map LNAPL contamination which is illustrated by the decreased radar signal amplitude and increased resistivity. | |||
TO cite this article:LU Qi,LIU Cai,FENG Xuan, et al. Detection of LNAPL contamination with GPR and resistivity surveys[OL].[25 November 2011] http://en.paper.edu.cn/en_releasepaper/content/4451870 |
3. A fully polarimetric borehole radar based numerical modelling: fully polarimetric radar responses to synthesized fractures | |||
Zhao Jianguo | |||
Earth Science 09 July 2010 | |||
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Abstract:A fully polarimetric borehole radar system with four combinations of dipole and cylindrical slot antennas was developed to acquire fully polarimetric data sets in drilled boreholes. To better under the fully polarimetric response to subsurface fractures with different roughness, in this study, synthetic fractures with different roughness are generated on a computer via fractal theory based simulation techniques. Quantitative assessment for the roughness of synthetic fractures is possible by use of three main parameters: the fractal dimension, the rms roughness at a reference length, and a length scale describing the degree of mismatch between the two fracture surfaces, allowing future detailed study of mechanical and transport properties of fractures and fully polarimetric radar response on them. Next, a 3D sub-grid FDTD numerical simulation is used to synthesize fully polarimetric data sets with synthetic fractures as primary reflectors. Based on the synthetic data sets, it is possible to evaluate the applicability of different radar polarimetry analysis approaches to physical characterization of subsurface fractures in future. | |||
TO cite this article:Zhao Jianguo. A fully polarimetric borehole radar based numerical modelling: fully polarimetric radar responses to synthesized fractures[OL].[ 9 July 2010] http://en.paper.edu.cn/en_releasepaper/content/4378517 |
4. polarimetric calibration approaches of fully polarimetric borehole radar | |||
Zhao Jianguo | |||
Earth Science 29 January 2008 | |||
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Abstract:A fully polarimetric borehole radar system with four combinations of dipole and cylindrical slot antennas was developed to acquire fully polarimetric data sets in drilled boreholes. This system in conjunction with several radar polarimetry techniques has proved to be a good alternative to physical subsurface fracture characterization. Furthermore, we presented that such polarimetry techniques, namely Pauli decomposition, eigenvector-based decomposition, Durden-Freeman decomposition and polarimetric anisotropy parameter methods, could provide comparable performances in terms of fracture characterization and classification. Polarimetric calibration to determine a scattering matrix (Sinclare matrix) is the foremost procedure in the radar polarimetry processing chain. In this paper, we experimentally implement and evaluate two polarimetric calibration approaches, namely 1) cross-hole polarimetric calibration and 2) single-hole polarimetric calibration, utilizing a fully polarimetric data sets acquired at a specific borehole test site. Both polarimetric calibration approaches can guarantee the further implementation of radar polarimetry techniques, and especially, the single-hole polarimetric calibration will be very meaningful to practical applications | |||
TO cite this article:Zhao Jianguo. polarimetric calibration approaches of fully polarimetric borehole radar[OL].[29 January 2008] http://en.paper.edu.cn/en_releasepaper/content/18471 |
5. The characteristic of tsp prediction | |||
He Xianqi,Zhu Ziqiang | |||
Earth Science 15 August 2005 | |||
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Abstract:Multi-component seismic exploration record both p-waves and shear waves,or s-waves,so it can get more information of the subsurface than convention seismic exploration.Tsp is a method of three-componet seismic survey system. it can be continuously used as an accompanying measure to the tunneling construction. | |||
TO cite this article:He Xianqi,Zhu Ziqiang. The characteristic of tsp prediction[OL].[15 August 2005] http://en.paper.edu.cn/en_releasepaper/content/2660 |
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