Influence of grain size, shape and compaction on georadar waves: example of an Aeolian dune

TL;DR

This study investigates how grain size, shape, and compaction influence GPR wave reflectivity in aeolian dunes, using analytical models and real data to understand subsurface features.

Contribution

It introduces integrated analytical models linking grain parameters to GPR permittivity and validates them with field data from Chadian desert dunes.

Findings

Grain properties significantly affect GPR reflectivity.

Models accurately predict GPR wave velocity and reflections.

Dunes contain diverse bounding surfaces with distinct reflection characteristics.

Abstract

Many Ground Penetrating Radar (GPR) profiles acquired in dry aeolian environment have shown good reflectivity inside present-day dunes. We show that the origin of this reflectivity is related to changes in grain size distribution, packing and/or grain shape in a sandy material. We integrate these three parameters into analytical models for bulk permittivity in order to predict the reflections and the velocity of GPR waves. We consider two GPR cross-sections acquired over Aeolian dunes in the Chadian desert. The 2D migration of GPR data suggests that dunes contain different kinds of bounding surfaces. We discuss and model three kinds of reflections using reasonable geological hypothesis about Aeolian sedimentation processes. The propagation and the reflection of radar waves are calculated using the 1D wavelet modelling method in spectral domain. The results of the forward modelling are in good accordance with real observed data.