Seismic monitoring of geomorphological processes: tracking mobile sources

Abstract

With a 2-Dimensonal (2-D) seismological array deployed in the Illgraben catchment (Switzerland) during the of summer 2011, we have detected and located with a high spatio-temporal resolution the geomorphic processes (mainly rockfalls and debris flows) that were triggered during rainstorms over a 100-day period. We succeeded in following the effects of a rock avalanche in the upper catchment and that evolved downstream into a debris flow. Its propagation gave rise to a secondary hillslope event (bank collapse). Such a sequence highlights the potential of seismic monitoring to survey in near real-time the two-way link that exists between hillslopes and channels. Further analysis of the seismic signals allowed us to extract characteristics of channel flows (velocity, rheology and energy) and their downstream evolution. Our results indicate that seismic monitoring can give substantial new insights into hillslope and channel processes and help enhance natural hazard early warning systems. Further development of the seismic surveying of surface processes will enable the tracking of mobile sediments in a landscape.