Identifying causes of ground-penetrating radar reflections using time-domain reflectometry and sedimentological analyses

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1046/j.1365-3091.2000.00304.x.

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Authors

Remke L. van Dam, Wolfgang Schlager

Abstract

Ground-penetrating radar (GPR) is a geophysical technique widely used to study the shallow subsurface and identify various sediment features that reflect electromagnetic waves. However, little is known about the exact cause of GPR reflections because few studies have coupled wave theory to petrophysical data. In this study, a 100- and 200-MHz GPR survey was conducted on aeolian deposits in a quarry. Time-domain reflectometry (TDR) was used to obtain detailed information on the product of relative permittivity and relative magnetic permeability, which mainly controls the GPR contrast parameter in the subsurface. Combining TDR data and lacquer peels from the quarry wall allowed the identification of various relationships between sediment characteristics and the product of relative permittivity and relative magnetic permeability. Synthetic radar traces, constructed using the TDR logs and sedimentological data from the lacquer peels, were compared with the actual GPR sections. Numerous peaks in the product of relative permittivity and relative magnetic permeability, which are superimposed on a baseline value of 4 for dry sand, are caused by potential GPR reflectors. These increases in the product of relative permittivity and relative magnetic permeability coincide with the presence of either organic material, having a higher water content and relative permittivity than the surrounding sediment, or iron oxide bands, enhancing relative magnetic permeability and causing water to stagnate on top of them. Sedimentary structures, as reflected in textural change, only result in possible GPR reflections when the volumetric water content exceeds 0.055. The synthetic radar traces provide an improved insight into the behaviour of radar waves and show that GPR results may be ambiguous because of multiples and interference.

DOI

https://doi.org/10.31223/osf.io/h2t34

Subjects

Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Sedimentology

Keywords

Ground-penetrating radar, modeling, petrophysics, sedimentology, GPR, Dielectric impedance, EM signals, lacquer peels, magnetic permeability, magnetic susceptibility, permittivity, TDR, time-domain reflectometry

Dates

Published: 2018-05-07 15:17

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License

GNU Lesser General Public License (LGPL) 2.1

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