Book/Dissertation / PhD Thesis

FZJ-2013-05898

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Full-waveform inversion of crosshole GPR data for hydrogeological applications

Klotzsche, A. (Corresponding author)FZJ*

2013
Forschungszentrum Jülich GmbH, Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-915-7

Please use a persistent id in citations: http://hdl.handle.net/2128/5641

Abstract: High resolution and precise characterization of aquifers is needed to improve the understanding of flow and solute transport processes. Decimeter-scale and high contraststructures caused by changes in the porosity or clay content can have a dominant effect on hydraulic processes within an aquifer. Such heterogeneities or layering in aquifers can be related to preferential flow paths or impermeable clay lenses and can act as electromagnetic low-velocity waveguides. Crosshole ground penetrating radar is able to provide shallow subsurface electrical properties, viz. dielectric permittivity and electrical conductivity, and has proven a powerful tool to map and characterize aquifers due to the method’s high resolution and sensitivity to porosity and soil water content. Ray-based methods, which incorporate only a small part of the measured signal in the inversion, such as first-arrival travel times and first-cycle amplitudes, are not able to detect such layers. In contrast, the crosshole GPR full-waveform inversion, which considers the entire waveform or significant parts thereof, is able to resolve sub-wavelength high resolution images and can detect high contrast layers. Recently, a novel 2D time-domain vectorial full-waveform crosshole radar inversion was introduced that significantly improves the model resolution compared to standard ray-based techniques. This GPR full-waveform inversion is modified by allowing an optimized acquisition setup that significantly reduces the acquisition time and computational costs. The improved algorithm is employed to invert crosshole GPR data acquired within a gravel aquifer in the Thur valley, Switzerland, using the ray-based results as starting models. Compared to the ray-based inversion, the results from the full-waveform inversion show images with significantly higher resolution. The simulated traces of the final model, obtained by the full-waveform inversion, fit the observed traces very well in the lower part of the section and reasonably well in the upper part of the section. By incorporating the vadose zone and the water table in the starting models and inversion domain, we are able to improve the initial results and resolve unprecedented sub-wavelength high resolution images for permittivity and conductivity in the entire inversion domain including a high permittivity layer between 5 m - 6 m depth. This high permittivity layer acts as an electromagnetic low-velocity waveguide and is caused by an increased porosity indicating a [...]

Keyword(s): Dissertation

Note: Dissertation, RWTH Aachen, 2013

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Contributing Institute(s):

1. Agrosphäre (IBG-3)

Research Program(s):

1. 246 - Modelling and Monitoring Terrestrial Systems: Methods and Technologies (POF2-246) (POF2-246)

Appears in the scientific report 2013

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Database coverage:

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