1 DETECTION OF GROUND MOTION IN THE LISBON REGION WITH PERSISTENT SCATTERER INTERFEROMETRY (PSI)

Abstract: We present evidence of ground motion detected in and around Lisbon with Radar Interferometry (Persistent Scatterer Interferometry- PSI). The work was done in the scope of GMES Terrafirma project, and two datasets of PSI data were used, with different orbital tracks. The first, provided by Tele Rilevamento Europa, is a standard TRE's PSInSAR processing chain H1 map of the Lisbon area. It covers the period from 1992 to 2003 and uses 55 Synthetic Aperture Radar Scenes from the ESA satellites ERS1/2 (orbital track 452, descending pass). The second set of data spans the period 1992-2006 and was provided by Altamira Information: it consists of (1) a standard SPN H1 product map of the area to the South of Lisbon, and (2) the result of running the SPN medium resolution processor for the Lisbon area and northwards. The Altamira maps were produced using 100 SAR scenes from both ERS1/2 and ENVISAT satellites (orbital track 223, descending pass). The delivered PSI maps give, for the spanned period, the mean velocity (in the line of sight of the satellite) and velocity time series for over 500.000 points in the area. The PSI maps were interpolated, detrended, contrast-enhanced, and compared with mapped geological features, soil classes, aeromagnetic and gravimetric data. At a regional scale, the results show a correlation between deep geological features inferred from geophysical techniques and psi-derived velocity patterns. At a more local scale, the main results are the detection of an area of ground subsidence (~6Km2) in the centre of Lisbon, and of another area possibly affected by slope movement in the north of Lisbon, close to the main highway. 1