Subsidence and evolution of the Thessaloniki plain, Greece, based on historical leveling and GPS data

Comparison of historical leveling and of recent GPS data reveal that the wider Thessaloniki plain (North Greece), a 2500 years old delta, has subsided in the last 50+ years up to 3.5 m. These results are consistent with independent estimates of subsidence in the suburbs of Thessaloniki and testify to a plain-wide effect. Rather localized increased subsidence resulting from hydrocompaction due to intense pumping is superimposed on the plain-wide subsidence. The latter seems to mimic the long-term tendency of landscape change, as the correlation between recent surface deformation and deformation derived from boreholes reveals. Furthermore, differential subsidence seems to control the flow of rivers and the overall morphology of the delta. The significance and necessity of geoid corrections in the comparison of historical and GPS data is also indicated.