Numerical modeling of landslide generated seismic waves

Gravitational instabilities such as debris flows, landslides or avalanches play a key role in erosion processes at the surface of the Earth and other telluric planets. On Earth, they represent one of the major natural hazards threatening population and infrastructure in volcanic, mountainous, seismic and coastal areas. One of the main issues in terms of risk assessment is to produce tools for detection of natural instabilities and for prediction of velocity and runout extent of rapid landslides. The lack of field measurements of the dynamics of natural landslides due to their unpredictability and destructive power, prevents investigating the mechanical properties of the flowing material that appears to be very different from experimental granular flows in the laboratory. In this context, the analysis of the seismic signal generated by natural instabilities provides a unique paradigm to study flow dynamics and discriminate the physical processes at play during their emplacement along the slope. Potentially, it is possible to infer information about the “landslide source” from the seismic signal produced during the initial collapse and the subsequent flow along the natural terrain. However, the process of reverse dynamic analysis is complex and must take into consideration the role of topography, mass of the landslide, flow dynamics, and wave propagation on the recorded signal. We use here numerical modeling of the landslide and of the generated seismic waves to address this issue. We show that (i) numerical simulation of landslide and generated seismic waves well match the observed low frequency seismic signal, (ii) topography effects on landslide dynamics play a key role in the observed seismic signal, (iii) simulation of the seismic wave makes it possible to discriminate between the alternative possible scenario of flow dynamics and to provide estimates of the rheological parameters during the flow. As a result, unique data on natural flow dynamics could be obtained through analysis of seismic signals generated by landslides of significant size that are recorded by local or regional seismic networks.