Ground penetrating radar for the detection of Quaternary sedimentary features in the Rhine River Valley

Ground Penetrating Radar (GPR) is a high frequency (from 10 MHz to 1 GHz) electromagnetic (EM) method which provides high-resolution images of near-surface structure (Smith and Jol, 1995). The depth of investigation depends on the frequency used and on the medium crossed by EM waves, and for low-loss geological materials it does not exceed 50 m (Davis and Annan, 1989). In some cases, GPR data show strong diffraction hyperbolae due to objects on the ground. EM waves propagate with little attenuation in air and conductive surface objects (power lines, metallic fences) and trees are strong reflectors, so reflections from above ground features are often present in GPR data (Sun and Young, 1995). In July 1997 a series of GPR lines were acquired in the seismically active Rhine Valley. We try to image by GPR the geometry of Quaternary sedimentary deposits and identify possible recent faults hidden under a vegetal cover. Some GPR profiles show strong diffraction hyperbolae due to the surface objects on the ground. The purpose of this article is to show the methodology of the acquisition and some preliminary results of GPR processing and interpretation.