Analysis of recent ground subsidence in the Sibari plain (Italy) by means of satellite SAR interferometry-based methods

This work attempts to map recent land subsidence on the Sibari plain in Calabria region (Southern Italy), by exploiting vertical velocity values and time series of persistent scatterer interferometry (PSI) synthetic aperture radar (SAR) data acquired in the period 1992–2011 by different satellite systems. After reviewing other sources and rates of subsidence recorded by previous works since the beginning of the Holocene, this paper presents the spatial distribution of the current settlement rates showing that subsidence is due to the compressible alluvial sediments of the plain, but that in recent times it is mostly due also to human activities. In fact, according to the most recent monitoring period (2009–2011), downward motion rates are recorded as being only localized within site-specific industrial areas, such as the ‘Sibari Lakes’ nautical and residential centre and Corigliano Calabro Industrial Zone. The temporal analysis of persistent scatterers (PS) time series, carried out through the PS-Time program, adds further useful information, finally highlighting that, in these areas, subsidence has positively decreased or stabilized from the second semester of the year 2010. This work shows that PSI measurements provide support in the quantitative evaluation of known subsidence process and that the analysis of time series allows effective detection of the temporal evolution trends of the phenomenon, such as changes or deceleration in displacement rates, not otherwise visible by merely considering the average velocity.