Calibration of the Swiss plate geophone system at the Zinal field site with direct bedload samples and results from controlled flume experiments

The Swiss plate geophone (SPG) system is an indirect bedload surrogate monitoring technique used to quantify bedload transport and retrieve information about the grain-size distribution from the recorded seismic signal. However, the SPG system still requires direct measurements of bedload transport for calibration. In addition to a field calibration campaign carried out in 2019 at the Navisence stream in Switzerland, a series of prototype flume experiments was conducted to further investigate the variability of the SPG system for different bedload transport conditions. By reproducing natural flow conditions in the flume and using grain size distributions of bedload samples collected at the Navisence stream, we identified the importance of vibrations caused by larger grains impacting a neighboring plate or the surrounding concrete. This improves our understanding how the SPG signal response changes with increasing grain sizes.