Exploitation of Amplitude and Phase of Satellite SAR Images for Landslide Mapping: The Case of Montescaglioso (South Italy)

Abstract

Pre-event and event landslide deformations have been detected and measured for the landslide that occurred on 3 December 2013 on the south-western slope of the Montescaglioso village (Basilicata Region, southern Italy). In this paper, ground displacements have been mapped through an integrated analysis based on a series of high resolution SAR (Synthetic Aperture Radar) images acquired by the Italian constellation of satellites COSMO-SkyMed. Analysis has been performed by exploiting both phase (through multi-image SAR interferometry) and amplitude information (through speckle tracking techniques) of the satellite images. SAR Interferometry, applied to images taken before the event, revealed a general pre-event movement, in the order of a few mm/yr, in the south-western slope of the Montescaglioso village. Highest pre-event velocities, ranging between 8 and 12 mm/yr, have been recorded in the sector of the slope where the first movement of the landslide took place. Speckle tracking, applied to images acquired before and after the event, allowed the retrieval of the 3D deformation field produced by the landslide. It also showed that ground displacements produced by the landslide have a dominant SSW component, with values exceeding 10 m for large sectors of the landslide area, with local peaks of 20 m in its central and deposit areas. Two minor landslides with a OPEN ACCESS Remote Sens. 2015, 7 14577 dominant SSE direction, which were detected in the upper parts of the slope, likely also occurred as secondary phenomena as consequence of the SSW movement of the main Montescaglioso landslide.

Satellite radar data for back-analyzing a landslide event: the Ponzano (Central Italy) case study

“…The rapid motion tracking is an amplitude-based technique that is ideally suited for detecting and measuring the displacement rates that exceed those measurable with a standard multiinterferometric approach (Raspini et al 2015). In fact, the maximum displacement detectable between two acquisitions is equal to λ/4, where λ is the wavelength of the radar signal, 1.4 and 0.7 cm for C-and X-band sensors, respectively (Crosetto et al 2016).…”

“…The RMT algorithm allows tracking changes between two acquisitions of a SAR satellite directly working on the amplitude information contained in the images. The offset, i.e., the component of the displacement vector along the range and azimuth directions, is calculated by performing a standard cross-correlation analysis on the two overlapping SAR images (Raspini et al 2015). The precision of this analysis, based on the speckle tracking, is in the order of 1/50th to1/ 20th of an image pixel (De Zan 2014) and depends on the coherence of the image, the dimension of the investigated area (in terms of number of pixels), and on the signal-to-noise ratio (Raspini et al 2015).…”

“…The offset, i.e., the component of the displacement vector along the range and azimuth directions, is calculated by performing a standard cross-correlation analysis on the two overlapping SAR images (Raspini et al 2015). The precision of this analysis, based on the speckle tracking, is in the order of 1/50th to1/ 20th of an image pixel (De Zan 2014) and depends on the coherence of the image, the dimension of the investigated area (in terms of number of pixels), and on the signal-to-noise ratio (Raspini et al 2015). In this case, a pixel patch of 50 pixels was used to calculate the amplitude offset, resulting in a precision of 2-3 cm (Paradella et al 2015).…”

“…Among them, two InSAR (interferometric synthetic aperture radar) techniques, PSInSAR (Ferretti et al 2001) and its evolution SqueeSAR (Ferretti et al 2011), have been widely exploited for the detection, mapping, definition of the state of activity, and monitoring of slow-moving landslide (Meisina et al 2008;Herrera et al 2011Herrera et al , 2013Bianchini et al 2013;Lu et al 2014;Notti et al 2014;Bianchini et al 2015a, b;Oliveira et al 2015;Raspini et al 2015;Bardi et al 2016;Calvello et al 2016;Béjar-Pizarro et al 2017).…”

“…For the characterization of the landslide, two different types of SAR processing techniques were chosen to (i) investigate the prefailure movements, exploiting the SqueeSAR analysis of C-band (RADARSAT-2 and Sentinel-1) SAR images, covering the period March 2003-February 2017 and focusing mainly on the monitoring of buildings and infrastructures; (ii) analyze the surface change during the main landslide deformation phase exploiting the amplitude signal through the rapid motion tracking (RMT) technique (Paradella et al 2015;Raspini et al 2015) applied to X-band TerraSAR-X SAR images acquired immediately before and after the landslide failure.…”