GA2015 SAR applicazioni frane parte1

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



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



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



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



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



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)


after photo-interpretation


after radar-interpretation

of ERS/ ENVISAT data


after radar-interpretation of RADARSAT

data

Tufillo

Instant mapping



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

Documents

GA2015 SAR applicazioni frane parte1