Time series synthetic aperture radar interferometry for ground deformation monitoring over a small scale tectonically active deltaic environment (Mornos, Central Greece)

摘要

This study deals with the estimation of subtle ground deformation at millimetric accuracy over the broader area of the Mornos River delta in Central Greece and its spatio-temporal distribution for the period between 1992 and 2009 through Persistent Scatterers Interferometry (PSI). The results showed that the majority of the scatterers, which show subsidence, are located within the delta plain with mean subsidence rates throughout the delta varying between-7.2 and +0.7 mm/y. An attempt is made to highlight the geographic distribution, the amplitude, and the causes of the observed delta plain subsidence. The positive correlation between the thickness of the fine-grained Holocene deltaic deposits and the subsidence rates reveals that the main cause is the natural compaction of sediments. The highest subsidence is observed at Bouka Karahassani village, which corresponds to the area of the most recently abandoned river mouth, which is intensely eroded by marine processes. Apart from the dominance of fine sediments in the study area, subsidence may also be attributed to submarine gravitational mass movements along the steep slopes of the prodelta as well as to the reduction of sediment load after the dam construction in 1979. The NW part of the delta seems to have been affected by aseismic slip along a NE-SW trending normal fault buried beneath the alluvial deposits of the Skala torrent fan.