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International Conference Vajont2013 - 8 October

International Conference Vajont2013 - 8 October

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3 notti studying and monitoring 3 notti studying and monitoring Presentation Transcript

  •  Padua, (October 8-10, 2013 ) Studying and monitoring large landslides with persistent scatterer data Davide Notti (*), Claudia Meisina (*), Alessio Colombo(**), Luca Lanteri (**) & Francesco Zucca (*) (*) Univ. di Pavia Dipartimento di Scienze della Terra e dell’Ambiente (**) ARPA - Piemonte - (Italy)
  • Studying and monitoring large landslides with persistent scatterer data INTRODUCTION  It is important to study large landslides of slow type. Even if a catastrophic collapse is improbable, they cause direct and indirect damage and are often associated with more rapid and dangerous landslides processes…. It is difficult to map and monitoring with traditional monitoring these landslides: low rate of movement, large extensions and logistic problems. The Persistent Scatterer Interferometry (PSI) techniques through an elaboration of temporal series of SAR satellite images allow to detect slow ground displacement (from few mm/yr to some cm/yr) where radar targets are widespread diffused. Several geological processes can be detected and monitored: subsidence, tectonics, periglacial processes and Extremely and very slow landslides (Cruden and Varnes, 1996) From 1992…. a progressive improvement of sensors, data covertures and processing International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data AIMS OF THE WORK Test the potentially of the PSI techniques in the study of large slow landslides (> 0.2 km2) At regional Scale: PSI capability to update landslides inventory (e.g. state of activity,..) and to monitor landslides in comparison with other instruments; At local scale: to analyze the large landslide kinematics through specific case histories in the Alps with particular focus on spatial and temporal analysis of the movement. The study ares is the NW Italy (Alps, Ligurian Alps, Langhe Hills and Oltrepò Pavese) The PS data used come from Radarsat (2003-2010) satellite and ERS (1992-2000) satellite processed with SqueeSAR™ (Ferretti et al, 2011) and PSInSAR™ (Ferretti et al, 2001) algorithm. Cooperation with: International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data GEOLOGICAL SETTINGS An Heterogeneous geological settings and wide areas (16’000 km2) Typical Processes:  Deep Seated Gravitational Slope Deformation (DSGSD) in the Alps especially calcschist and gneiss formations  Complex landslides (Oltrepò Pavese) in NW in the Apennine  Planar slide in Langhe Hills. Large landslides distributions (From IFFI landslides inventory) International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 1. Analysis at regional scale 1820 large landslides In the Alps about 60% of large landslides have useful PS (> 2 PS and > 30 PS/km 2) data (using Radarsat SqueeSAR). In Langhe Hills and Apennines the percentage of landslides with significant PS data is lower.   Only a small percentage of this have significant PS movement. International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 1. Analysis at regional scale  For DSGSD in the ALPS it is interesting also to consider the results for different lithologies: The percentage of landslides suitable for PSI analysis is related with talus and debris  The percentage of “PS active landsides” depends from the type of deformation and it is in agreement with previous study (Forlati et al, 1995) % suitable DSGSD for PS analysis (ALPS) 100% 90% 80% 70% Ductile deformations Brittle deformations Non Active Active 60% 50% 40% 30% 20% 10% 37% 14% 15% 0% 9% 0% Calchschist Minute Gneiss Augen Gneiss Limestone / Dolomite Serpentines International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 1. Analysis at regional scale PS and other monitoring systems in Piemonte Region PS + other Motoring 100% Only other Monitoring 80% Only PS Monitoring 60% No informations Respect to in situ monitoring PSI techniques provide a large database of landslides monitored. 40% 20% 0% ALPS Langhe Hills 100% Monitored landslide in The Alps vs average Vslope 90% The PS have not programmed distributions while monitoring system are installed where necessary 80% % Monitored Landslides On the other hand the monitoring systems are installed on landslides that present relevant movement. 70% 60% 50% 40% 30% 20% 10% 0% > -5 -5 / -10 -10 / -15 Vslope class International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 ) <- 15
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale The case Histories are representative of large landslides in the NW Alps. In Each case PS data play a different role…. 1 2 3 1) Alpe Baranca : Only PS 2) 3) Brenvetto: PS + GPS Rosone: Many monitoring systems, modeling. International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.1 DSGSD - Alpe Baranca Val Mastallone International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.1 DSGSD - Alpe Baranca DSGSD with brittle behavior: > relevant bulge of profile > Talus and rockfall International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.1 DSGSD - Alpe Baranca No monitoring, Geomorphological evidence After 2000 flood event a scarp appeared in the upper part of landslide, with PS it is possible to well discriminate the stable and unstable area Radarsat Data show faster movement then ERS International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.1 DSGSD - Alpe Baranca No monitoring, Geomorphological evidence After 2000 flood event a scarp appeared in the upper part of landslide, with PS it is possible to well discriminate the stable and unstable area Radarsat Data show faster movement then ERS International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.1 DSGSD - Alpe Baranca Good orientation Deep of sliding Surface unknown slope It was possible to resolve the EW and vertical component of the velocity Structural and geomorphological survey : Maffeo and Zanotelli, 2008 International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.1 DSGSD - Alpe Baranca but not significant acceleration was detected from TS, Radarsat data show a possible unwrapping errors Radarsat SqueeSAR 2001 2000 1999 1998 1997 10 1996 1995 ERS TS 2000 TS 0 -10 6 M Rainfall 1700 October 2000 Flood event 1400 -20 1100 -30 800 -40 500 -50 200 International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.2 Brenvetto Landslide N Soana, Valley (NW –Alps) close to Piamprato village. The landslides is located in the calcschist-ophiolitic complex between Gran Paradiso Massif and Sesia-Lanzo unit. Notable quaternary deposits glacial and colluvial deposits International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.2 Brenvetto Landslide A Complex landslides inside a DSGSD with strong evidence of deformation. Rockfall and rapid flow in the lower part of the slope (a relict landslide blocked the Soana stream) Possible damages to main road of the valley F. CARRARO, M. G. FORNO, P. C. BOCCA (1995) - Fenomeni gravitativi nell'alta Val Soana (Torino).Mem. Soc. Geol. It., 50 (1995), 45-58. International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.2 Brenvetto Landslide  PS and GPS show the relative strong movement of the complex landslide ( > 100 mm/yr) while DSGSD seems stable  A good agreement between data of the two different monitoring systems  Good PS spatial density allow to well define the landslide boundary International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.2 Brenvetto Landslide  PS and GPS show the relative strong movement of the complex landslide ( > 100 mm/yr) while DSGSD seems stable  A good agreement between data of the two different monitoring systems  Good PS spatial density allow to well define the landslide boundary International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.2 Brenvetto Landslide PS and GPS show a good agreement also for the time series. The movement is linear and is not significantly affected by rainfall or snow melting The velocity of this landslide is close to the limit of PS techniques, and some error of unwrapping can cause a little underestimation of movement International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.3 DSGSD - Rosone A Simple geological settings… Augen Gneiss International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.3 DSGSD - Rosone The landslides affect a pen-stock and hydro-electric plant so from 60’s it is monitored and modeled and many literature is available on this deformations.. Chiriotti, E. (1997): Mathematical modeling of the behavior of the large deep-seated gravitational slope deformation of Rosone (in Italian). PhD thesis, Politecnico di Torino, Italy; FORLATI F., GIODA G. & SCAVIA C. (2001) Finite element analysis of a deep seated slope deformation. In printing: Rock Mech. and Rock Eng. PISANI G., CASTELLI M. & C. SCAVIA C. (2010) - Hydrogeological model and hydraulic behavior of a large landslide in the Italian Western Alps. Nat. Hazards Earth Syst. Sci., 10, 2391–2406, 2010 RAMASCO M., STOPPA T. & SUSELLA G. (1989) - La deformazione gravitativa profonda di Rosone in Valle dell'Orco. Bollettino della Società Geologica Italiana, 108(03), 1989, pp. 401- PS can help? International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.3 DSGSD - Rosone Geomorphological map from Ramasco et al, 1989 International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.3 DSGSD - Rosone The PSI analysis is possible only in the sector A and B: - The sector A presents weak movements (5 mm/yr) in the eastern part and moderate movements (up to 10 mm/yr) - The sector B is characterized by moderate movements from 10 to 20 mm/yr. It is possible to see that a scarp borders a sub-sector with major movement. - The sector C does not have significant PS data. The GPS and optical measurements show a velocity from 45 up to 130 mm/yr. Direction of the movement: SSE; VLOS / VSLOPE = 0.65 International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.3 DSGSD - Rosone Sliding surface from inclinometers A B C Velocity mm/yr Landslide sectors GPS Optical Inclin. PSI Vslope A 12 5 < 10 4 - 10 B 20 15 10 - 30 10 - 20 C 45 - 130 38 - 43 n/a n/a 2001-2011 2001-2011 1991-2008 2003-2009 Period International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data 2. Analysis at local scale 2.3 DSGSD - Rosone The TS show a weak change in the trend Slow movement in the period 20052008 may be related to dry period;  No critical events during PS monitoring (2003-2009) International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data Conclusions At regional scale the most interesting results are :  in the Alps where the new processing techniques like SqueeSAR allow a high density of targets in the area covered by talus and debris more than 50 % of large landslides are suitable for PS analysis  Respect to in situ monitoring PSI techniques provide a large database of landslides monitored. On the other hand traditional monitoring is installed only where it is necessary.  Only few new large landslides were discovered with PS data. PSI techniques are more useful to update landslides state of activity and boundary.  The analysis of the data confirm that the DSGSD in calcschist formations in Western Alps are the more active than others. International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data Conclusions At local scale the most interesting results are : 1. Alpe Baranca DSGSD the role of PSI coupled with geomorphological analysis was fundamental because it was the only available monitoring system. PS data ERS (19922000) and RADARSAT (2003-2009) confirm the movement of the unstable sector before and after the paroxysm event of October 2000 (even if it is not registered). 2. The Brenvetto complex landslide. is an example of good integration of PSI and GPS data; both spatial and temporal distributions of the movement (time series) agree and well match the geomorphological evidence. 3. The Rosone Landslides is one of the most studied landslides in western Alps. In this case the PSI data confirm the already dense and heterogeneous monitoring system network and the other evidence. It was decided to integrate and largely replace the old monitoring system with a regular PSI analysis for the slower sectors (A and B). International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )
  • Studying and monitoring large landslides with persistent scatterer data Thanks for your attention ! International conference Vajont, 1963-2013 - Padua, (October 8-10, 2013 )