# Review of Satellite Interferometry for Landslide Detection in Italy
## 4 Spatial Distribution of the InSAR Applications
Verbania, Torino, and Cuneo are mountain provinces where InSAR data were exploited for landslide mapping [71; 72; 73; 74; 75; 76; 77; 78; 79; 80; 81; 82; 83; 84; 85]. The Langhe and Oltrepo Pavese Hills were the target of InSAR analyses as well [86; 87; 88]. The whole Apennine Arc registers hundreds of landslides every year. The Apennines are particularly prone to landslides, because of their geological and geomorphological evolution. Figure 2: Distribution of Interferometric Synthetic Aperture Radar (InSAR)-related applications for landslide studies in Italy in the period 1999–2019. The total number of applications for each region is included as well. Multiple provinces and regions can be the target of a single work. National-scale applications are excluded. The background image is an ESRI World Imagery Map. Although they have less energy of the relief with respect to the Alps, Apennines are dominated from North to South by clayey formations. Neotectonics, land use changes, and agricultural practices are other unfavorable conditions. Landslide characteristics differ locally, but their impact along the Apennine Arc produces considerable economic and human losses. In the Northern Apennines, Emilia Romagna and Liguria are two of the Italian regions paying a high price in terms of landslide impact. In these regions, InSAR techniques were a possible mitigation solution. In Emilia-Romagna, satellite-derived products were used for landslide mapping in the provinces of Bologna and Modena [89; 90; 91] and for single-site studies, such as the San Leo (Rimini Province [92]) and Berceto (Parma Province [93]) landslides. InSAR data were employed in Liguria to characterize and estimate the motion of single landslides such as Castagnola (La Spezia Province [94]), Lemeglio (Genova Province [95]), and Santo Stefano d'Aveto (Genova Province [96]). As a result of the high seismicity of some sectors of the Central Apennines, earthquakes are not negligible triggering factors for landslides. Thus, satellite interferometry was used to map moving slopes after mainshocks, such as the 2016 Antarctic earthquake, which heavily impacted Marche, Lazio, and Abruzzo [97; 98; 99], or the 2009 Aquila earthquake [100]. In the Central Apennines, InSAR has been also used for classical landslide mapping, such as in the Maiella relief [101; 102], in the Biferno Valley (Campobasso Province, Southern Molise [103]), and in Northern Molise [104; 105]. Other authors exploited the satellite interferometric data for single-site characterization, as in the case of the Mt. Frascare DSGSD (Macerata Province, Marche region [106]) or for the Ancona (Marche region [107]) and Agnone (Isernia Province, Molise region [108]) landslides. Campania, Basilicata, and Calabria are located along the Southern Apennines, and were the testing ground for successful InSAR studies. In Campania, some authors handled the InSAR results for landslide mapping and detection at the regional and provincial scale, aiming for the update of landslide inventories [109; 110; 111; 112; 113]. Single landslide studies were produced as well, such as for the Moio della Civitella (Salerno Province [114; 115]) and Calitri (Avellino Province [116; 117]) landslides. Basilicata region proposes some interesting landslide case studies from the Province of Potenza and Matera. Authors focus their analysis on the Montescalioso [118; 119; 120], Maratea [121], Avigliano [122], and Costa della Gaveta [123] landslides. Cosenza is the Calabrian province with the highest number of published research articles, 12 in total. InSAR was applied for landslide mapping and characterization in some municipalities, such as Lungro [124; 125], Verbicaro [126; 127], and Cerzeto [128]. Other relevant examples of single landslide characterization come from Gimigliano (Catanzaro Province [129]) and Papanice (Crotone municipality [130]). In addition, satellite interferometric products were exploited for landslide mapping and a state of activity assessment at the province and basin scale [131; 132; 133; 134; 135; 136].