Analysis of a large seismically induced mass movement after the December 2018 Etna volcano (southern Italy) seismic swarm
Michele Saroli, Matteo Albano, Simone Atzori, Marco Moro, Cristiano Tolomei, Christian Bignami, Salvatore Stramondo
Abstract
In the recent decades, satellite monitoring techniques have enhanced the discovery of non-catastrophic slope movements triggered by earthquake shaking involving old paleo-landslides with deep-seated sliding surfaces. Understanding the triggering and attenuation mechanisms of such mass movements is crucial to assessing their hazard. In December 2018, Etna volcano (southern Italy) began a very intense eruption, which was accompanied by a seismic swarm with magnitudes reaching 4.9. Synthetic aperture radar data identified local displacements over a hilly area to the west of Paternò village. We evaluated the contribution of seismically induced surface instability to the observed ground displacement by employing a multidisciplinary analysis comprising geological, geotechnical and geomorphological data, together with analytical and dynamic modelling. The results allowed us to identify the geometry and kinematics of a previously unknown paleo-landslide, which was stable before the volcanic eruption. The landslide was triggered by the light-to-moderate seismic shaking produced by the strongest event of the seismic sequence, namely, the December 26, Mw 4.9 earthquake. This observation confirms that seismic shaking has a cumulative effect on landslides that does not necessarily manifest as a failure but could evolve into a catastrophic collapse after several earthquakes.