ANALYSIS OF PSINSAR™ DATA FOR LANDSLIDE STUDIES FROM REGIONAL TO LOCAL SCALE Davide Notti (1) , Claudia Meisina (1) and Francesco Zucca (1) (1) University of Pavia – Earth Sciences Department - Via Ferrata, 1 - Pavia – ITALY - davide.notti@dst.unpv.it: ABSTRACT A PSInSAR™ analysis was carried out in a wide area of North-Western Italy (Piemonte and Lombardia regions) which cover a surface of about 40’000 km 2 . ERS 1-2 descending data (1992-2000) and, for some sectors, also RADARSAT data (2003-2007) in both acquisition geometries (ascending and descending) were used. The project was carried out in collaboration with ARPA Piemonte and Lombardia Region and SAR data were processed by Tele-Rilevamento Europa (TRE). This work analyses the capability of PSInSAR™ technique for the studies of landslides in different geological-geomorphological environments. The relationship between PSInSAR™ data and distribution of landslides (The Italian Landslide Inventory - IFFI Project) was studied firstly at regional scale, and then at local scale with a detailed in situ analysis for the most interesting sites. 1. INTRODUCTION PSInSAR™ [1] is an operational tool for precise ground deformation mapping on a sparse grid of phase stable radar targets (the so-called Permanent Scatterers, PS), acting as a “natural” geodetic network. This technique identifies, estimates and removes atmospheric distortions, leaving the PS displacement as the only contribution to the signal phase shift. The application of SAR data and, in particular, PSInSAR™ to detect and monitor surface deformations has advanced rapidly during the last decade, and it is now routinely applied to landslides: detection and monitoring [2-3-4], determination of landslide state of activity [5], modelling large slope instabilities [6-7]. This paper presents the results of a PSInSAR™ analysis carried out in a wide area of North-Western Italy (Lombardia and Piemonte regions) with an extension of about 40.000 km 2 . At regional scale the aims were: 1) to check the capability of the technique in the detection of the landslides in different geological and geomorphological environments using different sensors; 2) to verify how the PSInSAR™ technique can improve the results of the landslide database IFFI (the Italian Landslide Inventory [8]) in terms of landslide areal extent evaluation and unmapped phenomena detection. At local scale the aim was to check the capability of the PSInSAR™ in the study of landslide through the comparison with field surveys, aerial photo interpretation and traditional monitoring system. 2. GEOLOGICAL SETTINGS OF STUDY AREA In the study area it is possible to identify some main geological and geomorphological regions (Fig. 1) that present also a rather large difference in the type of landslides [9], geometry of slope, distribution of human settlements and land use. These factors are very important for the scatterer distribution and for the movement detections. Figure 1. Sketch showing the geological settings of the studied area. 1, 2, 3: Alps, Southern Alps, Morainic Hills; 4: Tertiary Piedmont Basin (Langhe and Monferrato Hills); 5, 6: Turin Hill-Apennines. The Alps, in the northern and western part of the area, are characterized by high slope gradients and the presence of foliated and massive rocks and by geomorphological settings derived from last glaciations. Sedimentary rocks (i.e. carbonates) are present in the Southern-Alps. The alpine environment is characterized by the presence of rock-falls/topples, large complex landslides and deep seated gravitational deformations (DSGSD). The human settlements are concentrated in the valley bottom, and in the lower part of slope. The Langhe and Monferrato region (or Tertiary Piedmont Basin), in the southern central part of Piedmont, presents a monocline succession of marl and sandstone layers and has asymmetrical valleys, with steep southeast-facing slopes and gentle northwest- facing slopes. In the Langhe and Monferrato area translational rock-block slides and shallow landslides make up the majority of landslides; the areas potentially affected by rock-block slides are called “CARG sectors”. The area presents a medium density of population with villages usually on the top of slope. The hilly southeastern part of Piemonte (Apennines and Torino Hill) is characterized by argillaceous and marly _____________________________________________________ Proc. ‘Fringe 2009 Workshop’, Frascati, Italy, 30 November – 4 December 2009 (ESA SP-677, March 2010)