Abstract
ABSTRACTMulti-temporal interferometric Persistent Scatterers Interferometry (PSI) techniques derive from the elaboration of satellite Synthetic Aperture Radar (SAR) images and represent a useful tool to detect ground millimetric movements over wide areas; thanks to non-invasiveness and high accuracy. However, PSI data are relative measurements estimated along the sensor Line Of Sight and referred to a chosen stable motionless reference point, so they lack absolute reference both in time and space. In this work, we propose a methodological procedure that exploits Global Navigation Satellite System (GNSS) data acquired from permanent stations to calibrate and fix relative InSAR results into conventional geodetic reference systems. Mean yearly velocities of PSI radar targets are corrected with GNSS values throughout operative procedures used in geodesy for crustal and local deformation data. The methodology is tested in Ravenna and Ferrara cities on the north-western Adriatic coast within the eastern alluvial plain of Po river (Italy), extensively affected by subsidence with strong spatial and temporal variations. The results reveal high rates of long-term subsidence of the study area and the effectiveness of the presented methodology for producing unique ground deformation maps over wide areas. .
Highlights
The Persistent Scatterers (PS) displacements and velocities calculated with Global Navigation Satellite System (GNSS) and Synthetic Aperture Radar (SAR) show differences due to the different LOS (Line of Sight) direction in which they are recorded
A belt of negative values is recognizable from Bologna to Rimini along the northern limit of Apennines chains
All of the GNSS data show lowering of the ground with different values depending on their site
Summary
Land subsidence is commonly defined as gentle and gradual lowering or sudden sinking of the ground surface (Galloway & Burbey, 2011). Subsidence phenomena mainly affect urban and greenhouses or nursery areas (Tomas et al, 2014; Del Soldato et al, 2018) because of water overexploitation, with serious consequences such as damage to linear infrastructures, e.g. bridges, roads or railways, and building stability issues due to differential settlement (Del Soldato et al, 2016; Faunt et al, 2016; Tomas et al, 2012). The monitoring of these phenomena plays a key role in the management of natural hazards for mitigating and minimizing the disaster losses and consequences. The Persistent Scatterers Interferometry (PSI) techniques (e.g. Ferretti, Prati, & Rocca, 2001; Berardino et al, 2002; Hooper et al, 2004; Ferretti et al, 2011) have been successfully adopted for a wide range of applications in disaster management, and it has extensively proven to be a valuable tool to detect ground deformations due to landslides (Solari et al, 2018; Del Soldato, Riquelme, et al, 2018a; Ciampalini et al, 2016) or subsidence (Bonì et al, 2017; Da Lio & Tosi, 2018; Da Lio & Teatini, 2018; Gao et al, 2018; Hung et al, 2017; Minh, Van Trung, & Toan, 2015; Aslan, Cakır, Ergintav, Lasserre, & Renard, 2018; Sun et al, 2017) or infrastructures stability (Di Pasquale et al, 2018)
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