Quantitative vulnerability assessment of buildings susceptible to slow-kinematic landslides

An approach for assessing the quantitative vulnerability, through empirical fragility and vulnerability curves, of masonry buildings exposed to slow-kinematic landslides is described. More in detail, the fragility curves express the probability of exceeding a given level of damage for a range of landslide intensity values. Starting from these ones, the vulnerability curve provides the mean level of damage severity to a given building (or aggregate of buildings) in relation to the landslide intensity value. The application of the vulnerability curve is exploited in the quantitative risk analysis (QRA), that quantifies the probability of a given level of loss.

The Department of Earth Sciences of the University of Florence has catalogued the severity damage landslide-induced to over four thousand masonry buildings gathered from in situ surveys in the northern Apennines. Moreover, to retrieve the fragility and, consequently, the vulnerability curves for buildings, the proposed method exploits the results of spaceborne Advanced Differential Interferometry SAR (A-DInSAR) analysis. In particular, such a method considers the landslide intensity value equal to the module of the vertical (up-down) and horizontal (east-west) deformation velocity obtained by properly combining ascending and descending Sentinel-1 DInSAR products, retrieved through the P-SBAS (Parallel-Small Baseline Subset) method developed at IREA-CNR.

This approach to assess the vulnerability has been integrated within the well-known QRA procedure, which is based on the application of the risk equation (R=H*V*E), where:

R is the landslide risk in terms of economic loss;

H is the hazard retrieved from the susceptibility map available for the entire Italian territory;

V is the vulnerability obtained directly from the equation of the vulnerability curve;

E is the exposure of buildings assessed from average real estate market parameters reported in the OMI (Osservatorio Mercato Immobliare).

The effectiveness of the proposed procedure has been tested over the municipality of Zeri (Massa-Carrara, Italy), where a large-scale landslide risk map has been produced. In particular, for each building of the study area, the hazard, the vulnerability, the exposure and the risk associated with it, are presented. The analysis estimates a total risk of 33.2 million euro for the Zeri municipality and the identification of specific buildings at highest risk. The provided result can be useful for the civil protection activities of the local administrator identifying areas with higher potentiality of damage on structures.