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Dispense su telerilevamento radar per frane e subsidenza, parte 1
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Filippo Catani
Radar interferometry applications for the
detection and monitoring of ground displacements
Department of Earth Sciences CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT
PRESIDENCY OF THE COUNCIL OF MINISTERS
Scheme of presentation
• Materials and methods – Satellite SAR interferometry – Ground-based SAR interferometry
• Applications – Inventory and motion survey – Monitoring and interpretation – Rapid mapping – Instant mapping – Failure forecasting – Early-warning – Emergency management
Sarno, 5 May 1998
153 victims Hundreds of homeless
Debris flows
Law n.267/1998: Landslide risk zonation Regional landslide inventories 2 million landslides mapped at 1:10.000 Lanslide risk areas ca. 10.000 areas classified at extremely high risk (R4) Social impact ca. 60 victims per year Economic impact ca. 1 - 2 billion Euro per year (0.15% of GDP) Unstable urban areas 1,306 to be stabilized 323 to be relocated
National risk zonation
Risk class Level Description Measures
R4 Very high Major risk for human life. Desctruction of buildings and infrastructures
Reconstruction forbidden, relocation or stabilization compulsory
R3 High Major losses for buildings and infrastructures. Possible risk for human life
Severe building restrictions. Stabilization works required.
R2 Medium Expected damage for buildings and infrastructures. No risk for life
Medium building restrictions
R1 Low Limited expected loss General risk prevention measures
R0 Negligible No expected loss None
Pho
to in
terp
reta
tion
I1: Scarps, terraces, counterslopes
I2: Sharp variation of curvature in the longitudinal profile
I6: Sharp difference in vegetation inside/outside the landslide
I3: Irregular drainage system, water ponds, internal drainage depressions, stream channel deviation
I4: Bedrock outcrops, soil erosion, denudation
I5: Presence of rapid-growth vegetation
1. Active (moving) – R4
2. Suspended (seasonally) – R4
3. Dormant (recurrent) – R3
5. Naturally stabilized – R2-R1
6. Artificially stabilized – R2-R1
7. Relict – R0
State of activity and risk zonation
UNESCO WP/WLI (1993)
PS technique
Satellite SAR interferometry
Department of Earth Sciences CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT
PRESIDENCY OF THE COUNCIL OF MINISTERS
θ=23°
Radar Satellites
SAR = Synthetic Aperture Radar
Radar satellites
Cosmo Sky Med
Etna
1’ acquisition 2’ acquisition
R1
Δ r
T0 T0+Δt Time Time
R1= R2
Permits to assess ground deformations with centimetric accuracy
Laion Landslide
SAR interferometry
San Francisco
Bay
Permanent Scatterers technique
multi-image processing
tem
po
100 Km 100 Km
ESA - ERS
35 giorni
Dataset of SAR images
pixel by pixel analysis
Processing technique of SAR images which allows to assess deformations with millimetric accuracy on single specific points (PS), coincident with highly reflective elements on the ground surface
San Francisco International Airport
Ascending and descending data
LiSA technique
Ground-based SAR interferometry
Department of Earth Sciences CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT
PRESIDENCY OF THE COUNCIL OF MINISTERS
Portable SAR apparatus known as LISA (Linear Synthetic Aperture Radar), developed by the Joint Research Centre of the European Commission
Ground based SAR interferometry
Continuous-wave stepped-frequency (CW-SF) radar based on a Network
Analyser (NWA) operating in the frequency band 17.0-17.1 GHz
Ground-based InSAR
The synthetic aperture is obtained sliding the antennas
along a linear rail
2.8m
target area
Rx Tx
sled
source NWA
computer
linear rail
:
European Commission Joint Research Centre
Acquisition of raw data
Network
Analyzer
Interferometry Image 1
Image 2
Interferogram (phase difference)
phas
e w
rapp
ing LO
S displacement (m
m)
Phase Wrapping: Large displacement generates fringes
Decorrelation: Rapid motion causes “salt &
pepper” texture
Coherence ( 0 <Γ <1) gives an estimate of the error in measured differential phase
Phase wrapping and decorrelation
Interferogram on DTM
Arno River Basin
Inventory and motion survey
Department of Earth Sciences CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT
PRESIDENCY OF THE COUNCIL OF MINISTERS
PS ERS descending 1992-2002
total: 327 942 PS
PS ERS ascending 1992-2002
total: 263 321 PS
Landslide inventory map
27 270 mapped landslides 8.8 % landslide density
74% earth slides and flows 19% shallow landslides and creep 5% debris flows 2% others
LegendLandslide polygons
attiv
instab
quiesc
Landslidelines
attivinatt
PS ascendingVel (mm/y)") -29.18 - -5.00") -4.99 - -3.00
") -2.99 - -1.25
") -1.24 - 1.25
") 1.26 - 3.00
") 3.01 - 5.00
") 5.01 - 29.05
PS DescendingVel (mm/y)$+ -29.18 - -5.00
$+ -4.99 - -3.00
$+ -2.99 - -1.25
$+ -1.24 - 1.25
$+ 1.26 - 3.00
$+ 3.01 - 5.00
$+ 5.01 - 29.05
G PS_rufina
PS and landslide map
active inactive dormant
active inactive dormant
active inactive
A
D C
B
E
F
Updating landslide inventory
C’
Landslide A Activity: confirmed Boundary: modified
Landslide B Activity: modified Boundary: modified
Landslide E New detection
Landslide F Activity: modified Boundary: confirmed Landslide D
New detection
Landslide C Activity: modified Boundary: modified
MATRIX OF ACTIVITY ERS < 2mm ERS > 2mm
ENVISAT < 2 mm Stable Dormant
ENVISAT > 2 mm Active (reactivated)
Active (continuos)
Activity matrix
HAZARD MAP
Expected loss: R = ~ 5.6 billion Euro in 30
years (0.5°/° GDP)
Risk Map: R= H·V·E
Revised hazard area with PS information
!( 5.01 - 29.05
!( 3.01 - 5.00
!( 1.26 - 3.00
!( -1.24 - 1.25
!( -2.99 - -1.25
!( -4.99 - -3.00
!( -29.18 - -5.00
Vel (mm/y)APSA
stabilizzata
quiesc
instab
attiv
Landslide
B B
A A
5
5
Arno River
The Carbonile landslide
Active Inactive Dormant Stabilized
Stabilization works (drainage wells & subhorizontal drainages)
Effectiveness of stabilization measures
Cirò Marina
Monitoring and interpretation
Department of Earth Sciences CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT
PRESIDENCY OF THE COUNCIL OF MINISTERS
PS RADARSAT ascending 2003-2005
Displacement = 4-12 mm/year
PS RADARSAT descending 2003-2005
Displacement= 4-8 mm/year
Reconstruction of the slip surface • Graphical method for reconstructing
the slip surface (Carter & Bentley, 1985; Cruden, 1986) used in Structural Geology
• Input data: position of the main scarp and displacement vectors within the landslide mass
• Assumption: rigid deformation within each slice (Mertie, 1947)
Reconstruction of the slip surface
Pro
dond
ità(m
p.c
.)
Distanza (m)
Sezione CD
N1 N6N3 N4 N5 N7 N8O1O2
O4
V2
V3
V4
V5
V6V7
V8
Pro
dond
ità(m
p.c
.)
Distanza (m)
Sezione EF
Interpolation
depth (m)
250
0
N
Interpolation of multiple sections
Data available only above the sea level
Extrapolation
depth (m) 350
0
N
Extrapolation of the sections below the sea level based on a constant reduction of the local inclination of the slip surface
Possible interpretation
Prof
ondi
tà
Distanza (m)
Sezione Porto Turistico
Presence of multiple slip surfaces
Shallow landslide in the area of the harbour
N
depth (m b.s.l.) 350
0
depth (m) 350
0
Comparison with bathymetry
Multi-beam by UNIROMA1-DST (F. Chiocci)
Estimated landslide volume = 1 billion m3 = 1 km3
Cerzeto (CZ)
Rapid mapping
Department of Earth Sciences CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT
PRESIDENCY OF THE COUNCIL OF MINISTERS
Cavallerizzo di Cerzeto: 7 march 2005
Satellite ERS1/2
Orbit descendent
Startdate 15/09/1992
Enddate 05/01/2001
No. of images 70
No. of PS 4642
Satellite RADARSAT
Orbit ascendent
Startdate 18/03/2003
Enddate 26/11/2005
No. of images 38
No. of PS 7869
Ikonos image rendered on DEM
and PS
Cavallerizzo di Cerzeto
Initial landslide map (PAI)
Cavallerizzo di Cerzeto
after photo-interpretation
Cavallerizzo di Cerzeto
after radar-interpretation
of ERS/ ENVISAT data
Cavallerizzo di Cerzeto
after radar-interpretation of RADARSAT
data
Tufillo
Instant mapping
Department of Earth Sciences CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT
PRESIDENCY OF THE COUNCIL OF MINISTERS
Tufillo
GPRS data
transmission
ENVISAT ascending 2002-2006
Punto Tufillo 469120E 4640895N (UTM 33)
0
2
4
6
8
10
12
14
16
18
20
24/05/2002 10/12/2002 28/06/2003 14/01/2004 01/08/2004 17/02/2005 05/09/2005 24/03/2006 10/10/2006
Time [days]
Dis
plac
emen
t [m
m]
velocity = 9 mm/year