In situ and satellite long-term monitoring of slow clayey landslides and of the structures built on them

This paper reports the results of a long-term monitoring of the slow movements of two deep earthflows in tectonized clay shales of southern Apennines. The cumulated movements have caused over the years severe damage to buildings and infrastructure, with important social and economic costs. Deep and superficial displacements, along with pore water pressures, are being monitored since 2005; in some areas of the slope, displacement monitoring by inclinometers started about 30 years ago. The kinematics of the landslides have been clarified sufficiently on the basis of ground-based measurements. On the other hand, the mostly N-S orientation of displacements, and the rather limited urbanization, make it rather challenging to monitor the area by satellite interferometry methodology. To minimize such problem, satellite data relative to areas where the displacements and their directions are clearly determined by inclinometers and GPS were analysed at the most detailed scale of analysis. The data validation allowed to confidently exploit remote sensing results in a wider area. Thus, images acquired by the COSMO-SkyMed satellite system, supplemented by ERS and Envisat data (available since 1993), allowed the reconstruction of the kinematic history of the urbanized area even where inclinometer displacement series were available only over short periods. Indications about the effectiveness of the remedial measures constructed in the area under study could also be obtained.