Shallow Shear Wave Reflection Seismic on Firn and Ice – Insights, Challanges, and Opportunities From a Small Scale Experiment at Colle Gnifetti

In the summer season 2010, a small shallow reflection seismic experiment was carried out on the overburden firn and ice cover of the Colle Gnifetti, Monte Rosa group, Swiss/Italian Alps. This site is widely used for method testing, since the physical properties of ice are similar to polar regions. The whole experiment was designed to explore the scope of the shallow high-resolution vibroseis method for seismic targets of the firn and ice mass of nearly 60 m thickness. A special part of the experiment was the exploration of vibratory shear wave reflection seismic capabilities in such an environment, which was never done before. The small ELVIS vibrator system was used to generate seismic shear waves received by common planted horizontal geophones in a SH-SH (source and receivers arranged both perpendicular to the profiling direction) configuration on two profiles, arranged as a cross setup. The resulting seismic sections of both profiles clearly show the boundary from ice to rock (evaluated by ice coring in 2005), the structure dip and also deeper events within the underlaying rock up to 150 m in depth. Seismic velocities within the ice overburden were used to derive elastic parameters combined with the density function derived from the ice coring. The results of this experiment show promising new prospects for the vibratory shear wave reflection method on glaciers, firn, and ice.