Imaging very Shallow Sand Deposits with High Resolution SH Wave Reflection Seismic

The main objective for this case study was to map the geological structures along a railway ramp of the great belt tunnel in Denmark. Special focus was put on mapping a thin near surface sandy deposit situated between two clay till units. The purpose for the survey was to provide a detailed geological model as basis for improving the groundwater pumping in the ramp. A SH-wave reflection seismic survey provided a high resolution imaging in the very shallow subsurface and was also the primary source for the geological interpretations. Refraction seismic analysis of the reflection records, surface wave measurements and VSP measurements in two boreholes were also carried out and together with the SH reflection result and available borehole data a detailed geological model was created.