Università degli Studi di Firenze. Università degli Studi di Palermo

Advanced interpretation of

PSI time series for mapping and

characterization of geological hazards:

Naro (Italy) case study

C

IGNA

F.

, D

EL

V

ENTISETTE

C., L

IGUORI

V., C

ASAGLI

N.

Terrafirma Workshop

Università degli Studi di Firenze

Department of Civil and Environmental Engineering

Department of Earth Sciences

CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT

PRESIDENCY OF THE COUNCIL OF MINISTERS

Outline

•

Persistent Scatterer Interferometry

•

Test area: Naro (Italy)

–

Geomorphologic and historical background

–

PSI time series analysis

–

Final results

Persistent Scatterer Interferometry

Multi-image

processing

TI

ME

n

SAR

images

Average LOS deformation rate

(precision ~ 0.1-1 mm/yr)

Displacement time-series

(precision ~ 1-3 mm on single measure)

Identification of potential

anomalies and/or accelerations

d

t

d

t

d

t

Persistent Scatterer Interferometry

Test area: Naro (Italy)

Geomorphologic & historical background

Vanelle St.

Gesù Maria St.

February 4

th

_{, 2005 event}

• Severe ground deformations

• Opening of fractures (aperture up

to 5-10 cm) in buildings and road

infrastructure

• Last documented reactivations:

1997, 1942, 1940, 1934, 1908

Test area: Naro (Italy)

Geomorphologic & historical background

NW view

SE view

Morphologic scarps

Morphologic scarps

W view

First hypotheses

• landslide or tectonics?

Field observations

• NNW-SSE stress distribution

(same as regional tectonics)

• well-marked scarps of probable

Test area: Naro (Italy)

PSI time-series analysis

Vanelle St.

Gesù Maria St.



larger extension of

affected area



rapid displacements

detected in 2005

N. acquisitions

54

RSAT

Processed area

35

km

2

Identified PS

2587

Mean PS density

74

PS/km

2

Max PS density

1471

PS/km

2 -30 -20 -10 0 10 20 30 M a r-03 O ct -03 A p r-04 N o v -04 M a y -05 D e c -05 Ju l-06 Ja n -07 D isp la ce m e n t [ m m ] Time A1JZ8

LOS

displ

acemen

t

[mm]

Time

4

th

_{February 2005}

Test area: Naro (Italy)

PSI time-series analysis

-20 -15 -10 -5 0 5 10 15 20

M

ar

-03

Ju

l-03

N

o

v-03

M

ar

-04

Ju

l-04

N

o

v-04

M

ar

-05

Ju

l-05

N

o

v-05

L

O

S

d

is

p

la

c

e

m

e

n

t

[m

m

]

Time

PS Code: A04YZ Vel: 0.0 mm/yr Coher: 0.94

-20 -15 -10 -5 0 5 10 15 20

M

ar

-03

Ju

l-03

N

o

v-03

M

ar

-04

Ju

l-04

N

o

v-04

M

ar

-05

Ju

l-05

N

o

v-05

L

O

S

d

is

p

la

c

e

m

e

n

t

[m

m

]

Time

PS Code: A05SQ Vel: -11.6 mm/yr Coher: 0.93

-20 -15 -10 -5 0 5 10 15 20

M

ar

-03

Ju

l-03

N

o

v-03

M

ar

-04

Ju

l-04

N

o

v-04

M

ar

-05

Ju

l-05

N

o

v-05

L

O

S

d

is

p

la

c

e

m

e

n

t

[m

m

]

Time

PS Code: A05NX Vel: -5.6 mm/yr Coher: 0.78

-20 -15 -10 -5 0 5 10 15 20

M

ar

-03

Ju

l-03

N

o

v-03

M

ar

-04

Ju

l-04

N

o

v-04

M

ar

-05

Ju

l-05

N

o

v-05

L

O

S

d

is

p

la

c

e

m

e

n

t

[m

m

]

Time

PS Code: A05AB Vel: -4.6 mm/yr Coher: 0.79

Stability (S)

Linear trend (L)

Temporary change (T)

Permanent Change (P)

UNAFFECTED TARGETS

Test area: Naro (Italy)

PSI time-series analysis

Classification of PS time-series

UNAFFECTED TARGETS

d

t

d

t

AFFECTED TARGETS

d

t

d

t

Stability

Linear trend

Temporary

change

Permanent

change

Test area: Naro (Italy)

PSI time-series analysis

Classification of PS time-series

UNAFFECTED TARGETS

d

t

d

t

AFFECTED TARGETS

d

t

d

t

Stability

Linear trend

Temporary

change

Permanent

change

Very-high risk

,

historically known,

periodically recurring and

directly connected with

the 2005 reactivation

Medium risk

.

Fractures are isolated,

discontinuous and not

directly associated with

ground deformations in

the historical area

High risk

,

referable to geological

and tectonic structures

reactivated in 2005

Test area: Naro (Italy)

Preliminary risk mapping

Integration of PSI data

with geological,

structural and

geophysical surveys,

and distribution of

elements at risk

Concluding remarks

•

Naro



spatial and temporal behavior of 2005 deformations



larger extension than detected by field surveys



geological origin attributed to tectonics (Caltanissetta basin evolution)



surface evidence of deep-seated tectonic structures

•

Limitations of the PSI time series analysis



inappropriate model of phase variations through time (underestimation or

misunderstanding of real deformations; radar target exclusion)



aliasing of PSI measures (phase unwrapping errors; ambiguity)

•

Future perspectives



improvements using high resolution data (e.g. COSMO-SkyMed)

Thanks for your attention!

Francesca Cigna

francesca.cigna@unifi.it

Università degli Studi di Firenze

Department of Civil and Environmental Engineering

Department of Earth Sciences

CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT

PRESIDENCY OF THE COUNCIL OF MINISTERS

Università degli Studi di Palermo

Terrafirma Workshop

Frascati, 1

st

_{December 2010}