A method for locating rockfall impacts using signals recorded by a microseismic network

Background: Rockfall events are one of the most dangerous phenomena that often cause several damages bothto people and facilities. During recent years, the scientific community focused the attention at evaluating theeffectiveness of seismological methods in monitoring these phenomena. In this work, we present a quick andpractical method to locate the rebounds of some man-induced boulders falls from a landslides crown located inthe Northern Apennines (Central Italy). The reconstruction of the trajectories was obtained by means of backanalysis performed through a Matlab code that takes into account both the DEM (Digital Elevation Model) of theground, the geotechnical-geophysical characteristicsof the slope and the arrival times of the seismic signalsgenerated by the rock impacts on the ground. Results: The localization results have been compared with GPS coordinates of the points and videos footage acquiredduring the simulations, in order to assess the reliability of the method. In most cases, the retrieved impact points matchwith the real trajectories, showing a high reliability. Furthermore, four different cases have been identified as a functionof the geomechanical, geophysical and morphological conditions. Due to the latter ones, in some case it was necessaryto assume different values for the propagation velocity of the elastic waves in the ground, here assumed to be isotropicand homogeneous. Conclusions: This work aims at evaluating the effectiveness ofa quick and practical method to locate rockfallevents using a small-aperture seismic network. The obtained results indicate that the technique can providequantitative information about the area most prone toimpact of detached blocks. The method still presentssome uncertainty, but reducing some of the approximations (e.g. by better constraining the velocity model),it could lead to prompt and more accurate results, easily applicable to hazard estimates.