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Lotti, Alessia
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Lotti, Alessia
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- PublicationOpen AccessA method for locating rockfall impacts using signals recorded by a microseismic network(2017)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ;Background Rockfall events are one of the most dangerous phenomena that often cause several damages both to people and facilities. During recent years, the scientific community focused the attention at evaluating the effectiveness of seismological methods in monitoring these phenomena. In this work, we present a quick and practical method to locate the rebounds of some man-induced boulders falls from a landslides crown located in the Northern Apennines (Central Italy). The reconstruction of the trajectories was obtained by means of back analysis performed through a Matlab code that takes into account both the DEM (Digital Elevation Model) of the ground, the geotechnical-geophysical characteristics of the slope and the arrival times of the seismic signals generated by the rock impacts on the ground. Results The localization results have been compared with GPS coordinates of the points and videos footage acquired during the simulations, in order to assess the reliability of the method. In most cases, the retrieved impact points match with the real trajectories, showing a high reliability. Furthermore, four different cases have been identified as a function of the geomechanical, geophysical and morphological conditions. Due to the latter ones, in some case it was necessary to assume different values for the propagation velocity of the elastic waves in the ground, here assumed to be isotropic and homogeneous. Conclusions This work aims at evaluating the effectiveness of a quick and practical method to locate rockfall events using a small-aperture seismic network. The obtained results indicate that the technique can provide quantitative information about the area most prone to impact of detached blocks. The method still presents some 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.518 48 - PublicationRestrictedMicro-seismic monitoring after the shipwreck of the Costa Concordia at Giglio Island (Italy)A micro-seismic network was used for monitoring the wreck of the Costa Concordia cruise ship, wrecked and run agrounded along the Giglio Island coasts during the night of 13 January 2012, until its removal. The seismic traces were processed by means of real-time and ‘‘a posteriori’’ procedures to detect transients that could be ascribed to wreck movements on the sea bed to integrate this information in an early warning system for assessing the wreck stability. After a first discrimination of the transients using amplitude criteria we proceeded to the localization of the detected signals to focus the attention only on the transients originated in the shipwreck resting area. The results showed that most of the events localized on the wreck were likely related to human work activities or sudden internal brittle failure but not to displacements on the seafloor. Instead, the displacements are associated to the impact on the vessel of great sea storms which approach were well correlated with the increasing seismic noise at low frequency. The carried out procedures based on this unique dataset represent an opportunity to test seismic monitoring techniques also in not usual engineering context to support emergency management activities.
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