# Review of Satellite Interferometry for Landslide Detection in Italy
## 4 Spatial Distribution of the InSAR Applications  
Figure 2 presents the regional and provincial distribution of the papers collected. It is worth noting that multiple provinces can be the target of a single study. This is true for basin-scale works and for articles showing multiple case studies. The Arno River Basin, including five different Tuscan provinces, is an example of this [31; 32; 33; 34; 35; 36; 37; 38]. Video S1 proposes an additional visual interpretation of the temporal evolution of the scientific production at regional scale. InSAR has been applied for landslide studies in all Italian regions except for Sardinia. The regions with the highest number of applications are Sicily (35), Lombardy (26), and Tuscany (24). Of course, the lack of applications does not imply a lower level of attention paid to landslides. Although uncommon, some Italian provinces have an almost flat morphology (such as Southern Apulia or some coastal provinces along the Adriatic coast). In other areas, where landslides can occur or have occurred, interferometric products have simply not been chosen because of regional and local policies, due to, e.g., a lack of awareness of existing InSAR technologies, or technical aspects related to the landslide location and typology. Another factor is the inhomogeneous distribution of available radar imagery; for instance, Sardinia was covered by only a few ERS 1/2 and COSMO frames before the launch of Sentinel-1. Messina (19) and Perugia (16) are the two Italian provinces with the highest number of InSAR-related applications. In the last 10 years, the province of Messina has been periodically affected by intense rainfall events that triggered several landslides and caused severe damage and casualties. Most of the applications have been used in the municipalities of Giampilieri (e.g., [39; 40; 41]) and San Fratello (e.g., [42; 43; 44; 45; 40]) or in the Nebrodi range in general (e.g., [47; 48; 49; 50; 51; 52]). In the Perugia province, the Ivancich roto-translational landslide (Assisi municipality) has been widely studied with the aid of interferometric products [53; 54; 55; 56; 57; 58; 59; 60]. Sondrio (Lombardia, Northern Italy) is another province where interferometric data were frequently used (15 papers published). This Alpine region is characterized by the presence of several active landslides ranging between flank-scale Deep Seated Gravitational Slope Deformations (DSGSD) to rockfalls and rockslides [61; 62; 63; 64; 65; 66]. One of the first applications of InSAR to assess the state of activity of a rockslide comes from this province (Ruinon landslide, Santa Caterina Valfurva municipality [67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77; 78; 79]). InSAR data have been widely used for landslide monitoring along the Alpine Arc, such as in the Valle d'Aosta and Trentino-Alto Adige regions. Although different from a geological point of view, the current morphology of both regions was shaped by post-glacial processes. Large DSGSD and complex landslides, as well as rockfalls and rockslides, are led by the combination of glacial debuttressing, post-glacial erosion, and current climatic regimes. In Valle d'Aosta, InSAR has been exploited for regional and basin-to-valley-scale landslide mapping [70; 71; 72; 73; 74], as well as for single landslide characterization and monitoring. The Bosmatto complex landslide is an example of such an approach [75]. In Trentino-Alto Adige, the Corvara complex landslide (Bolzano Province) has been widely studied by means of InSAR. Corner reflectors, specifically designed for the installation in a high mountain environment, were deployed on the landslide to increase the number and quality of measurement points [76; 77; 78; 79]. A unique application of satellite interferometry comes from the Adige River Valley (Lavini di Marco site, Trento Province [80]), where InSAR was used to study slope buckling Piedmont is a region where landslides related to Alpine dynamics and shallow processes in hilly landscapes coexist.