Contribution of Permanent Scatterers technique to the analysis of natural subsidence in urban area and multi-temporal urbanization impact

Category Other
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Del Conte, Sara۱; Proietti, Chiara۱; Corazza, Angelo۲; Casagli, Nicola۱
Holding Date 04 October 2008

Satellite InSAR (Interferometric Synthetic Aperture Radar) has shown in recent years its capabilities in providing precise measurements of ground displacements. In the case of slow movements (up to few cm/year) affecting urban area, the multi-interferogram technique, such as the Permanent Scatters (PS) (developed by Tele-Rilevamento Europa, a spin-off company of the Politecnico di Milano University), are able to retrieve the spatial distribution of displacements and their evolution along the monitored period.
Thanks to the availability of archive dataset of SAR images acquired by the ERS1 and ERS2 satellites (ESA- European Spatial Agency) spanning from 1992 to 2002, and the present images by Envisat satellite (ESA) and Radarsat (CSA- Canadian Spatial Agency) spanning from 2003-to present, the PS analysis can be applied to provide the multi-temporal analyses of past movements (more than 15 years) and the monitoring of current ground movements. For these reasons the Italian Civil Protection Department (DPC) promoted a project (SAR.net) devoted to the development of a national satellite monitoring system, based on the interpretation of satellite data processed with PS technique, for monitoring and mapping ground movements over large areas.
The results obtained in the cities selected as test site for this monitoring system, are here presented.
The PS analysis allowed us to identify, at basin scale, the areas affected by subsidence. For these areas, the interpretation of PS data was integrated with geological maps, stratigraphic and geotechnical underground deposits characteristics, historical maps and recent urbanization plans.
At a detailed scale this integrated approach allows us not only to interpret the geological triggering factors of subsidence but also to investigate the urbanization impact on ground deformation. In fact, satellite data provide relevant multi-temporal information data for detecting and monitoring ground surface deformations related to the typology and thickness of deposits, their geotechnical characteristics and the urban land cover that influence consolidation factors.
The results obtained confirm that this methodology is a valuable tool for the subsidence factors analysis in urban area and for the natural hazard forecasting and prediction in charge of subsidence risk management. This approach fits the requirements of Civil Protection authorities that are frequently faced to emergencies induced by the occurrence of ground movements in built-up areas.