Self-excitation process due to local seismic amplification and earthquake-induced reactivations of large landslides

摘要

During the year of 2002 two large landslides were triggered in Italy by the 06/09/2002 Palermoearthquake (Ml=5.6) and the 31/10/2002 Molise earthquake (Ml=5.4),respectively close to Cerda (Sicily)and Salcito (Molise) villages. These landslides showed similar features: the involved volumes were in the orderof 20-40×106 m3 of varicoloured scaly clays; the extensions were about 1.5 kin; the landslides showedtranslational mechanisms with failure zones up to 50 m below ground level (b.g.l.); average S-wave velocityvalues up to 400 m/s were recorded within the landslide masses; the epicentral distance was about 50 km. TheNakamura analysis of ambient noise records pointed out significant amplification effects within the landslidemasses at about 1 Hz; these effects can be related to both the pre-existing landslide masses and the geologicalsetting. Given the observed amplification effects,a self-excitation process can be hypothesised for the analysedseismically induced reactivations.