Self‐excitation process due to local seismic amplification responsible for the reactivation of the Salcito landslide (Italy) on 31 October 2002

Abstract

[1] An integrated numerical and geophysical approach was used to investigate the role of local seismic amplification in the reactivation of the Salcito landslide (Italy) after the Molise earthquake of 31 October 2002. Numerical stress-strain analysis with FLAC 5.0 FDM software, performed in dynamic configuration, showed that the 1 Hz frequency was consistent with landslide instability conditions. The Fourier spectrum of the triggering earthquake showed two main peaks occurring at 1 and 2 Hz, respectively, which could be related to local effects. The analysis of H/V spectral ratios of ambient noise records obtained in the landslide area, evidenced amplification effects in the 1-3 Hz range. On the basis of an engineering geology model, numerical modeling of both 1-D and 2-D seismic wave propagation was conducted using linear and nonlinear solutions. The simulation outputs showed (1) a 1 Hz amplification ascribable to 2-D effects due to a landslide mass lying within a basin-like geological structure; (2) a double-peak amplification at about 2 and 3 Hz, respectively, ascribable to 1-D resonance of the landslide mass; and (3) 1-D plus lateral wave effects within the landslide mass in the 2.5-3.5 Hz frequency range. These findings suggest that local amplification of ground motion by the Salcito landslide mass may generate a self-excitation process responsible for its reactivation.

Earthquake-induced ground failures in Italy from a reviewed database

“…However, new studies that have retrieved information about some historical earthquakes, published after the first release of the catalogue, made it necessary to revise the related data. Reference was made particularly to papers referring to specific earthquakes, such as those by and Serva et al (2007) that detail the ground effects that occurred in some earthquakes in historical (Sannio 1805) and recent times (Irpinia 1930 and; studies referring to specific ground phenomena, such as the catalogue of liquefaction by Galli (2000); and studies referring to specific localities where earthquakes have produced some outstanding effect (Prestininzi, 1995;Mancini et al, 2001;Bozzano et al, 2004Bozzano et al, , 2008Bozzano et al, , 2011. The CEDIT database reports approximately 2000 localities where ground failures were triggered by 166 earthquakes that occurred in the last millennium in Italy for which information about the occurrence of ground effects can be retrieved from historical documents.…”

Supervised Method of Landslide Inventory Using Panchromatic SPOT5 Images and Application to the Earthquake-Triggered Landslides of Pisco (Peru, 2007, Mw8.0)

“…The source magnitude controls the area affected by landslides [1] relating the ground motion decay with distance to the epicenter or to the fault plane (e.g., [3]). However this generic law is affected by different factors: (1) a significant over-abundance of landslides in the hanging walls of ruptured thrust faults relative to the footwalls rate are reported (e.g., [4,5]), showing the effect of the dynamics of the fault rupture on the landslide distribution; (2) the greater erosion rate due to precipitations observed after the earthquake [8,10] shows that earthquakes are found to interact non-linearly with precipitations; (3) the site effect, or amplification of the seismic waves due to shear-wave velocity contrast between the landslide material and the stable material [11,12] or topographical particularities like ridges [9]. This topographic control on co-seismic landslides has also been pointed out through different parameters: convexity [7], slopes, proximity from ridges and crests [6,9].…”

The role of near-field interaction between seismic waves and slope on the triggering of a rockslide at Lorca (SE Spain)

“…a sketched slope profile constituted of flat top and bottom and of a constant dip face) on seismic ground motions has been studied by using numerical modeling Bouckovalas and Papadimitriou, 2005;Nguyen and Gatmiri, 2007;Papadimitriou and Chaloulos, 2010;Lenti and Martino, 2011), as reliable field measurements are difficult to obtain because wave scattering due to step-like slope geometries require an unrealistically dense distribution of recording stations. These studies have demonstrated that (i) step-like slope topographies may lead to intense amplification and de-amplification irregularly along the slope, depending on the slope geometry; and (ii) the possible interactions among the seismic input, the slope and preexisting landslide masses depend on seismic properties such as frequency content, directivity and the peak of ground acceleration (Bozzano et al, 2008(Bozzano et al, , 2011aMartino and Scarascia Mugnozza, 2005;Del Gaudio and Wasowsky, 2010;Lenti and Martino, 2011).…”

“…Nevertheless, the maximum distance of occurrence of landslides may significantly change as an effect of local site conditions (Gallipoli et al, 2000;Wasowsky and Del Gaudio, 2000;Havenith et al, 2002Havenith et al, , 2003aMartino and Scarascia Mugnozza, 2005;Meric et al, 2007;Bourdeau and Havenith, 2008;Bozzano et al, 2008;Bordoni et al, 2010;Bozzano et al, 2011b;Havenith et al, 2003a, b). In particular, seismically-induced disrupted landslides can be strongly influenced by the orientation of local discontinuities and the topographic amplification of the ground motion (Crawford and Curran, 1981;Harp and Jibson, 2002;Moore et al, 2011;Lovati et al, 2011).…”