GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 Figure 2: maps showing the location of Earthquake Induced Landslides identified and used for this study (left) and the composite seismogenic sources of the DISS database (DISS Working Group, 2021) used for building preliminary EILs scenarios for each potential hypocenter location (right). The small red dots located along the seismogenic sources represent the possible hypocenter locations used for the floating approach. These hypocenters were located at a depth corresponding to the 2/3 downdip width of the fault and are shifted 4 km apart. The map on the left shows also with the red and blue star symbols the epicenters of the earthquakes associated to the EILs. The blue star indicates if a shakemap was available for the specific earthquake. As a second step, the implemented database was used to develop new empirical attenuation relationships between the EILs density and the distance from the epicenter as a function of the earthquake magnitude. Then, we subdivided seismic events into three magnitude classes to account for the different extent of the maximum area affected by EILs and released energy. The three classes are as follows: Class 1, M < 5.5; Class 2, 5.5 ≤ M < 6.5, and Class 3, M ≥ 6.5. Based on the locations of EILs and of epicenters, we set circular search areas with a 5 km large moving window and calculated for each area the cumulative density. We found that the cumulative density decreases with the distance following a power law relationship, with coefficients of determination variable between 0.95 and 0.99 according to the magnitude class, and that the maximum distance including 95 th percentile of landslides increases with increasing magnitude range. In particular, the 95 th percentile distance, i.e. the distance within which 95% of EILs are expected to occur, is 42 km for earthquakes of Class 1, 66 km for those of Class 2, and 77 km for those of Class 3. In addition, using the shakemaps of 38 out of 159 historical earthquakes of our dataset, we developed an empirical relationship between EILs density and PGA values. The shakemaps of historical earthquakes were recently published by the Istituto Nazionale di Geofisica e Vulcanologia and are available at http://shakemap.ingv.it/shake4/. EILs density was computed by classifying PGA