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Marek Graniczny, Polish Geological Institute in Warsaw (Poland)
Andrzej Piotrowski, Polish Geological Institute (Poland)
Anna Piatkowska, Polish Geological Institute in Warsaw (Poland)
Zbigniew Kowalski, Polish Geological Institute in Warsaw (Poland)
Janusz Wasowski, Consiglio Nazionale delle Ricerche - Istituto di Ricerca per la Protezione Idrogeologica (Italy)
Fabio Bovenga, Consiglio Nazionale delle Ricerche - Istituto di Studi Sui Sistemi Intelligenti per L'automazione (Italy)
Jolanta Cyziene , Lithuanian Geological Survey (Lithuania)
Jonas Satkunas, Lithuanian Geological Survey (Lithuania)
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Results of ground motion observations in the European Lowland Areas are presented from three case studies performed in Vilnius, capital of Lithuania, Szczecin located in the north-western Poland at the border with Germany, and Inowroc³aw located in the Central Poland. These three localities seem to be characteristic of European Lowlands. They are covered by thick and differentiated Quaternary deposits and reveal different forms of the glacial landscape. In two cases alluvial deposits of the big rivers are important element of the geological setting ? Odra River in Szczecin and Neris River in Vilnius. The presence of salt structures in the Inowroc³aw area constitutes an additional element of the geological setting, which is also typical for Polish ? German Lowlands.
Permanent Scatteres Interferometry (PSI) methodology, developed at Politecnico di Milano, and similar innovative multi-temporal DInSAR techniques extend the applicability of radar interferometry from regional to local-scale geological investigations of ground subsidence and slope instability. The PSI analysis allows the identification of numerous radar targets (the PS) where very precise displacement information can be obtained.
Up till now, on the basis of the results from traditional monitoring methods (eg. precise-levelling), the European Lowlands were generally considered as very stable areas. PSI methodology gives a new outlook at ground deformation phenomena.
For instance, the PSI dataset of Vilnius is characterised by irregular spatial distribution of moving and stable PS. The interpretation of the Vilnius PSI dataset has enabled to show certain relations between the downward moving PS and geological conditions and geodynamic phenomena in several places of the city and its neighbourhood. Some of the examined examples included subsidence linked to the presence of compressible deposits (organic, lacustrine), mass movements, changes in groundwater level and loading by big buildings.
The PSI data set of the Szczecin area indicates subsidence of the alluvial deposits in different parts of the Odra Valley, among them in the vicinity of the harbour and shipyard. The presence of subsiding buildings within the Valley can be related to the compaction of the sediments including organic material (about 8 m thick). Subsidence in the town of Inowroc³aw was reported in several places. It is linked to the salt exploitation. The analysis of the Inowroc³aw PSI dataset indicates complex relations between the salt diapire dynamics and moving PS. In the middle of the salt structure covered by gypsum cap both uplift and subsidence were observed.
Clearly, the PSI results should be further verified by using precise geodetic measurements (leveling and GPS) as well as data on groundwater extraction. Nevertheless, the reported case studies show the importance of innovative PSI methods for ground motion investigations in the lowland areas.
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