Department of Earth Sciences
CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT PRESIDENCY OF THE COUNCIL OF MINISTERS
Radar interferometry applications for the detection and monitoring of ground displacements Filippo Catani
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
Debris flows 153 victims Hundreds of homeless
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
Photo interpretation
I1: Scarps, terraces, counterslopes I2: Sharp variation of curvature in the longitudinal profile I3: Irregular drainage system, water ponds, internal drainage depressions, stream channel deviation I4: Bedrock outcrops, soil erosion, denudation I5: Presence of rapid-growth vegetation I6: Sharp difference in vegetation inside/ outside the landslide
State of activity and risk zonation 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 UNESCO WP/WLI (1993)
Department of Earth Sciences
CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT PRESIDENCY OF THE COUNCIL OF MINISTERS
Satellite SAR interferometry PS technique
Radar Satellites SAR = Synthetic Aperture Radar
θ=23°
Radar satellites
Cosmo Sky Med
Etna
SAR interferometry Time
T0 R1
Time
T0+Δt
R1= R2
Δr 1’ acquisition
2’ acquisition
Permits to assess ground deformations with centimetric accuracy
Laion Landslide
Permanent Scatterers technique pixel by pixel analysis ESA - ERS San Francisco International Airport
multi-image processing
San Francisco Bay
tempo
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
35 giorni
100 Km 100 Km
Dataset of SAR images
Ascending and descending data
Department of Earth Sciences
CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT PRESIDENCY OF THE COUNCIL OF MINISTERS
Ground-based SAR interferometry LiSA technique
Ground based SAR interferometry
Portable SAR apparatus known as LISA (Linear Synthetic Aperture Radar), developed by the Joint Research Centre of the European Commission
Ground-based InSAR Continuous-wave stepped-frequency (CW-SF) radar based on a Network Analyser (NWA) operating in the frequency band 17.0-17.1 GHz
target area
Tx
Rx
sled
linear rail 2.8m
source NWA
:
computer
The synthetic aperture is obtained sliding the antennas along a linear rail European Commission Joint Research Centre
Acquisition of raw data
Network Analyzer
Interferometry Image 1
LOS displacement (mm)
Image 2
phase wrapping
Interferogram (phase difference)
Phase wrapping and decorrelation Phase Wrapping: Large displacement generates fringes
Decorrelation: Rapid motion causes “salt & pepper� texture
Coherence ( 0 <Î&#x201C; <1) gives an estimate of the error in measured differential phase
Interferogram on DTM
Department of Earth Sciences
CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT PRESIDENCY OF THE COUNCIL OF MINISTERS
Inventory and motion survey Arno River Basin
PS ERS descending 1992-2002 total: 327 942 PS
PS ERS ascending 1992-2002 total: 263 321 PS
Landslide inventory map
74% earth slides and flows 19% shallow landslides and creep 5% debris flows 2% others
27 270 mapped landslides 8.8 % landslide density
PS and landslide map
Legend Landslide polygons
Landslide lines
attiv
attiv
instab
inatt
quiesc
PS ascending
PS Descending
Vel (mm/y)
Vel (mm/y)
")
-29.18 - -5.00
$ +
-29.18 - -5.00
")
-4.99 - -3.00
$ +
-4.99 - -3.00
")
-2.99 - -1.25
$ +
-2.99 - -1.25
")
-1.24 - 1.25
$ +
-1.24 - 1.25
")
1.26 - 3.00
$ +
1.26 - 3.00
")
3.01 - 5.00
$ +
3.01 - 5.00
5.01 - 29.05
$ +
5.01 - 29.05
")
G
PS_rufina
Updating landslide inventory Landslide A Activity: confirmed Boundary: modified Landslide B Activity: modified Boundary: modified
A
B F
active inactive active inactive dormant
active inactive dormant
C Landslide F Activity: modified Boundary: confirmed Landslide C Activity: modified Boundary: modified
D Câ&#x20AC;&#x2122; E
Landslide D New detection Landslide E New detection
Activity matrix
MATRIX OF ACTIVITY
ERS < 2mm
ERS > 2mm
ENVISAT < 2 mm
Stable
Dormant
ENVISAT > 2 mm
Active (reactivated)
Active (continuos)
HAZARD MAP
Risk Map: R= H路V路E
Expected loss: R = ~ 5.6 billion Euro in 30 years (0.5掳/掳 GDP)
Revised hazard area with PS information
Effectiveness of stabilization measures Stabilization works (drainage wells & subhorizontal drainages) Landslide attiv Active
Arno River
instab Inactive
quiesc Dormant
B
stabilizzata Stabilized
B
APSA Vel (mm/y)
5 A
A 5
The Carbonile landslide
!(
-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
Department of Earth Sciences
CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT PRESIDENCY OF THE COUNCIL OF MINISTERS
Monitoring and interpretation Cirò Marina
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 O4
Sezione EF N1
O1
N3
O2
N5
N4
Prodondità (m p.c.)
V2 V3
V4
V5 V6 V7 V8
Distanza (m)
Prodondità (m p.c.)
Sezione CD
Distanza (m)
N6
N7
N8
Interpolation N
0
depth (m)
250
Interpolation of multiple sections Data available only above the sea level
Extrapolation N
0 350
depth (m)
Extrapolation of the sections below the sea level based on a constant reduction of the local inclination of the slip surface
Possible interpretation
ProfonditĂ
Sezione Porto Turistico
Distanza (m)
Presence of multiple slip surfaces Shallow landslide in the area of the harbour
N
0
350
depth (m b.s.l.)
Comparison with bathymetry
0
depth (m) 350
Multi-beam by UNIROMA1-DST (F. Chiocci)
Estimated landslide volume = 1 billion m3 = 1 km3
Department of Earth Sciences
CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT PRESIDENCY OF THE COUNCIL OF MINISTERS
Rapid mapping Cerzeto (CZ)
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 photointerpretation
Cavallerizzo di Cerzeto after radarinterpretation of ERS/ ENVISAT data
Cavallerizzo di Cerzeto after radarinterpretation of RADARSAT data
Department of Earth Sciences
CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT PRESIDENCY OF THE COUNCIL OF MINISTERS
Instant mapping Tufillo
Tufillo
GPRS data transmission
ENVISAT ascending 2002-2006
Punto Tufillo 469120E 4640895N (UTM 33) 20
18
16
Displacement [mm]
14
12
10
8
6
4
2
0 24/05/2002
10/12/2002
28/06/2003
14/01/2004
01/08/2004
17/02/2005
Time [days]
velocity = 9 mm/year
05/09/2005
24/03/2006
10/10/2006