COSMO-SKYMED AND RADARSAT-2 JOINT ANALYSIS AND MODELING FOR THE

EVALUATION OF POTENTIAL DEFORMATIONS CAUSED BY THE LARGE MASS MOVEMENTS

SURROUNDING THE FIASTRA LAKE DAM

Matteo Albano1, Christian Bignami1, Roberto Devoti1, Fabrizio Lombardini2, Marco Moro1, Marco Polcari1, Sergey

Samsonov3, Michele Saroli4, Salvatore Stramondo1, Federico Viviani21 2 3 4

Outline

• Study Area & Previous work• Deep-seated Gravitational Slope Deformation• Dataset• SAR velocity maps• GPS & Corner Reflectors installation• SAR Tomography 4D• Conclusions

Study area

• The rectangle shows the area of Frascare Mountain, in central Apennines at the top of the Sibillini Mountain thrust next to the Lower Lias–Upper Eocene calcareous formations.

• It contain Oligocene marls that formed during the Tortonian–Lower Pliocene compressive tectonic phase

Deep-seated Gravitational Slope Deformation (DGSD) characteristics

• Involved mass volume (of about hundreds km3);• Width and length extension (few kilometers);• Thickness (from about 60 m up to hundreds of meters);• Movement rates (from few millimeters per year up to

few centimeters per year);• The mechanical and dynamic behaviour is affected by

gravitational creep phenomena.

DGSD typology

• Sackung or rock flow• Sliding planes are not always

recognizable

• Lateral spread• It is due to rocks with a fragile

behavior superimposed on a more plastic bedrock

• Block slide• Sliding planes (preexistent or

new) are well defined

Morphological characteristics

Visible from local survey or (better) from aerial photo (stereo)• Double ridges• Linear and bent depressions (natural trenches)• Scarps and counterscarps• Bulging lower slopes

• Photogeological analysis allowed to identify different morphological features that indicated DGSDs, such as double crest lines, scarps, counterslope scarps, slope-parallel trenches, fractures, open fissures and small depressions that were linearly aligned tothe NE.

• Podalla DGSD has been assigned to sackung “category”, moving towards NW and controlled by NE-striking. In addition it is characterized by a NW-dipping sliding plane up to approximately 500–600 m depth and there evolving in a shear zone.

• The top of the sackung is limited by the presence ofarcuated trenches.LEGEND1) slope waste deposits; 2) slides; 3) flows; 4) rock falls; 5) DGSD upper limit; 6) strata attitude; 7) normal faults and thrusts; 8) tectonized zones; 9) main edges of structural scarps; 10) trenches; 11) structurally conditioned downcutting stream.

Trenches near the top of Mt. Frascare. Greater trenches are mainly occupied by debris and vegetation. However, small recent trenches (on the right) are less open, not filled by debris, and do not contain vegetation.

Fresh crack widening up to a few cm per year. The crack has opened more than 0.5 m.

On field evidences

Previous studies• DInSAR SBAS (Small BAseline Subset)

technique applied to measure movement rate for selected test areas.

• The selected test areas were previously identified by both aerial photos and using 32 ERS radar images spanning 1993-2000.

• More than 15 cm of surface displacement along satellite LoS (Line of Sight) occurred across the Podalla DGSD.

• The displacement time series showed non-linear deformation rates, including accelerated movement correlated with strong rainfall.

• The highest deformation rates occurred at very fresh-looking extensional fractures occurred in the Upper Trench zone.

Available sataset

• COSMO-SkyMed (CSK) and Radarsat-2 (R2) images• CSK dataset is composed by 23 SLC images ->

November 2010 to December 2013, desc. orbit• R2 dataset, it consisted of 36 Standard -3 (S3)

images -> January 2009 and April 2013, asc. orbit

• CSK processed by IPTA Multi-baseline approach• R2 processed by SBAS approach

CSK results• 30 interferograms generated

• Max baseline: spatial 200 m, temporal 400 days

• Topo phase removed by Tin-Italy DEM (10 m pixel resolution)

• 2.8 mm/yr max velocity detected in LoS

• Bottom part of DGSD is moving (??)

• No coherent points from the upper part of DGSD to be more confident about the results

• Further analysis will focus on the exploitation of CR for better constraining the deformation trend

R2 results• 50 interferograms generated

• Max baseline: spatial 200 m, temporal 400 days (Please check and edit, can you add a time/space plot of interf.??)

• Topo phase removed by ASTER DEM (30 m pixel resolution)

Mm/yr or cm/yr ???

• R2 velocity LoS indicates stability of the DGSD

• Or very low rate non detectable with C-band sensors????

• Other comments????

GPS and CR installation• Installation campaign on December 10 & 11, 2014

• 2 CR installed: designed to match an X-band SAR sensor -> trihedral shape type, in perforated aluminium, and elevation pointing capability, with a side length of 60 cm

• 2 GPS receivers to have independent measurements (few meters far from the CRs)

Integrated Geodetic Station (IGS)

First GPS outcomes

• Observation period: Dec. 10, 2014 to June 24, 2015

• The distance between the two GPS stations is decreasing at a rate of -5.2 mm/yr (to be confirmed after a full annual cycle).

• Deformation may be triggered (or modulated) by heavy rain

Acknowledgements:Rainfall data supplied by: Regione Marche, Dip. Politiche Integrate di Sicurezza e per la Protezione CivileGPS data of station CAM1 supplied by : NetGeo, Topcon Positioning Italy S.r.l.

Time series of the baseline between Fiastra-Top vs.-Bottom station

First GPS outcomes cont.d

Time series of the baseline between the two Fiastra stations, Top (FIAA) and Bottom (FIAB) w.r.t. CAM1 station (at 14-16 km distance)• Both baselines are increasing with time, but at different rates

• The FIAA station seems more influenced by rainfall events

• Root-mean-squared (RMS) of residuals ~ 3mm

SAR 4D Tomography

• 4D Differential Tomography: 3D + time• Synergically integrate the DinSAR and the 3D SAR

Tomography concepts

Conclusions • X- and C-band data exploited to study Deep-seated

Gravitational Slope Deformations (DGSD)• ASI-CSA Joint Project• CSK results….tbd• R2 results …tbd• Preliminary GPS data ….and CR….

Future work•4D tomography•CR deformation analysis (new data acquisition is planned)•Update GPS time series