Central Italy seismic sequences-induced landsliding: 1997-1998 Umbria-Marche and 2008-2009 L 'Aquila cases.

In Italy, the Central Apennines are characterized by significant seismic activity. In this region, individual earthquakes and prolonged seismic sequences produce considerable ground effects, including landslides. In this work, we attempt a comparison of the distribution, types and abundance of slope failures produced by two recent seismic sequences in central Italy: (i) the September 1997 - April 1998, Umbria-Marche sequence, and (ii) the December 2008 - July 2009 (ongoing), L'Aquila sequence. Preliminary results indicate that significant similarities exist between the mass movements produced by the two earthquake sequences. Both sequences produced chiefly rock falls, topples and minor rock slides. The distribution of the slope failures matches the macroseismic intensity fields. For the L'Aquila earthquake, slope failures are most numerous in the area where surface deformation was largest. For both earthquake sequences, the number of slope failures decreases with increasing distance from the earthquake epicenters. The decay in the number of failures with the distance from the epicenters is approximate by an exponential law.