For water dynamics investigation in unsaturated (vadose) zones, ground penetrating radar is a popular hydro-geophysical method because it is non-invasive for soil, has high resolution and the results have a direct link with water content. Soil water content and soil hydraulic properties are two key factors for describing the water dynamics in vadose zones. There has been tremendous progress in soil water content and soil hydraulic properties estimation with ground penetrating radar. The purpose of this paper is to provide an overview of the application of ground penetrating radar for soil water dynamics studies. This paper first summarizes various methods for the determination of soil water content. including traditional methods in the surveys of surface ground penetrating radar, borehole ground penetrating radar, and off-ground ground penetrating radar, as well as relatively new methods, such as full waveform inversion, the average envelope amplitude method, and the frequency shift method. This paper further provides a review for estimating soil hydraulic properties with GPR according to the types of ground penetrating radar data. We hope that this review can provide a reference for the application of ground penetrating radar in soil water dynamics studies in the future.

Summary. Many ground penetrating radar (GPR) profiles acquired in dry aeolian environment have shown good reflectivity inside present-day dunes. We show that t

Ground-penetrating Radar (GPR) sections commonly suffer from strong scattered energy and weak reflectors with distorted lateral continuity. This is mainly due to the gradual variation of moisture with depth, dense lateral sampling of common-offset GPR traces (which are considered as zero-offset data), along with the small wavelength of the electromagnetic waves that is comparable to the size of the shallow subsurface dielectric heterogeneities. Focusing of the diffractions requires efficient migration that, in the presence of highly heterogeneous subsurface formations, can be improved by a detailed migration velocity model. Such a velocity model is difficult to develop because the common-offset antenna array is mostly used for its reduced time and cost in the data acquisition and processing stages. In such cases, migration processes are based on limited information from velocity analysis of clear diffractions, cores, or other ground truth knowledge, often leading to insufficient imaging. We have developed a methodology to obtain GPR sections with focused diffractions that is based on multipath summation, using weighted stacking (summation) of constant-velocity migrated sections over a predefined velocity range. The success of this method depends on the assignment of an appropriate weight, for each constant-velocity migrated section to contribute to the final stack, and the optimal width of the velocity range used. Additionally, we develop a postmultipath summation processing step, which consists of time-varying spectral whitening, to deal with the decrease of the dominant frequency due to attenuation effects and the additional degraded resolution expected by the constant migration summed images. This imaging strategy leads to GPR sections with sufficiently focused diffractions, enhancing the lateral and the temporal resolution, without the need to explicitly build a migration velocity model.

Since 1994 the students of the third year of the Ecole de Physique du Globe de Strasbourg (EPGS) start their last school year (roughly in mid-September) by performing a geophysics field camp. Students (including teachers) participate in hands-on geophysical studies using the methods of seismic reflection and refraction, gravity, magnetics, electrical resistivity, electromagnetics, and ground penetrating radar (GPR). They collect data with modern equipment; they process, model, and interpret the data with workstation and PCs; and they present their results in both oral and written form.

The use of GPR data multipath summation on data acquired over parallel study lines is presented here within the framework of a study on the effects of natural hazards on cultural heritage areas in order to image weak zones within carbonates, such as fractures and caverns. This study was realized at the archeological site of Xochicalco in Mexico, where fractures and caverns are potential sources of the degradation of the archeological remains. Dense parallel GPR study lines spaced every 0.25 m were surveyed using a 400 MHz monostatic antenna with the aim to image possible weak zones in three dimensions. We used a 2D imaging approach, namely, the method of multipath summation, which efficiently focused the scattered energy within the GPR sections. The study revealed, at depths of 1.6m and 1.8m, several linear events attributed to fractures, leading to the preliminary conclusion of this on-going project that cracks on the walls of the Quetzalcoatl Temple after a large earthquake in 2017 are prone to instability of carbonates rocks.