Increase of landslide activity after a low magnitude earthquake inferred by DInSAR interferometry
Abstract On August 16th, 2018, an Mw 5.1 earthquake struck the Molise region (central Italy), inducing 84 earthquake-triggered landslides that involved soil covers of clayey materials and flysch on gently-dip slopes predominantly. To quantify the spatio-temporal landslide activity in the months immediately after the earthquake, a Differential SAR Interferometry (DInSAR) analysis was carried out in a time span comprising two years before the earthquake and one followed, recognising both first-time and reactivated landslides. The results showed a clear increase in landslide activity following the low magnitude earthquake occurrence with respect to the one recorded in the same months of the previous years. Several coherent landslides (earth slides and earth flows) were observed following the seasonally recurrent rainfall events. Such an increase was observed for both reactivations and first-time landslides, showing a decrease of inactivity period as well as activity over wider periods. Furthermore, spatial density distribution of the landslides was investigated in the post-seismic time along transepts perpendicular and parallel to the direction of the tectonic element responsible for the seismic event, respectively. An asymmetrical distribution was deduced parallel to the fault strike with the higher number of landslides located inside the compressional sector according to a strike-slip faulting mechanism.