TXT-tool 4.039-3.2: How to Assess Landslide Activity and Intensity with Persistent Scatterer Interferometry (PSI): The PSI-Based Matrix Approach
Cigna, Francesca ; Bianchini, S. ; Casagli, N.
Feb - 2018
Book Title :

type: Book Section

Abstract
This paper provides a step-by-step analysis and discussion of the ‘PSI-based matrix approach’, a methodology that exploits ground deformation velocities derived through Persistent Scatterer Interferometry (PSI) for the assessment of the state of activity and intensity of extremely to very slow landslides. Two matrices based on historical and recent PSI data are designed respectively for landslides already mapped in preexisting inventories and for newly identified phenomena. A unique intensity scale is proposed applicable to both cases. An example application in the 14 km2 area of Verbicaro in Northern Calabria (Italy) is presented. For this sample site, PSI data derived from SAR (Synthetic Aperture Radar) images acquired by ERS1/2 and RADARSAT1/2 satellites in the period 1992–2011 are employed. Ground velocities measured along the satellite Line Of Sight (LOS) are projected along the maximum slope directions to derive more reliable deformation rates. An activity threshold of ±5 mm/year is determined by applying the average projected velocity of local slopes to the PSI data precision. The intensity threshold between extremely and very slow phenomena (16 mm/year) is reduced by ~20% to account for temporal and spatial averages, being applied to attribute representative velocities to each landslide. The methodology allows assessing the state of activity and the intensity for 13 of the 24 landslides pre-mapped in the 2007 inventory and for two newly identified phenomena. Results, as well as the major factors influencing the approach, are shown and discussed. Pending issues of the proposed methodology are critically tackled and include the lack of PSI data within the landslide boundaries, temporal coverage of the available estimates, need of field checks, and operative procedures to set the activity and intensity thresholds.

keywords : Landslides Persistent scatterer interferometry State of activity Intensity SAR interferometry PSI-based matrix