Seismically-induced landslide susceptibility evaluation: Application of a new procedure to the island of Ischia, Campania Region, Southern Italy

摘要

In this paper we present an approach for evaluating landslide susceptibility in seismic areas. It is known thatearthquake-induced landslide susceptibility is related to several, often interplaying, factors. Nevertheless, aneffective grade-2 zonation should be characterized by a good balance between simplicity, quickness andreliability. The GIS-based procedure we present employs only three factors that we believe are the mostsignificant in this susceptibility assessment: the type of outcropping rocks/soils, the slope angle and the MCSintensity. The local annual precipitation, certainly an essential factor, is considered here as a parameter whoseseasonal pattern is constant in time and space. Each of the three parameters is expressed as a Significancepercentage and the resulting Seismic Landslide Susceptibility level of an area is given by the average of thesignificances of the first two factors multiplied by the significance of the third factor. The procedure was set andtested on the volcanic island of Ischia (southern Italy), which was affected by several historical earthquake-induced landslides. The results of this susceptibility zonation test at Ischia show a very good match betweenthe distribution of the sources of historical landslides and the areas we identified as the most susceptible ones.