PS-InSAR analysis of Colli Albani volcanic area: … WS5...PS-InSAR analysis of Colli Albani...

PS-InSAR analysis of Colli Albani volcanic area:

comparison with in-situ data and modeled source to

define a possible H-3 scenario

Stramondo S.1, De Lotto P.2, Bignami C.1

1 Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy2 CESI, Milan, Italy

27/04/2009 TF Workshop, ESA-Esrin

27/04/2009 TF Workshop, ESA Esrin 2

Summary

Introduction

The Colli Albani volcanic complex

The SAR dataset and the PS-InSAR products (H-1)

GPS and leveling (H-2)

Data comparison

Preliminary model (H-3)

Conclusion

The Colli Albani volcanic area

The test site of H-3 product of Terrafirma project has been selected in the

Colli Albani volcanic area

Being close to the metropolitan area of Rome (about 15 km SE), this area is

of great interest for geophysicists

The Colli Albano volcano has a complex caldera, whose last eruptive

products have been dated at 20 ky

Since the Roman age the whole area has been interested by swarms of

shallow, moderate magnitude, earthquake events

The most important episode has been registered in 1989-1990.

327/04/2009 TF Workshop, ESA Esrin

The Colli Albani volcanic complex

• First volcanic product age ~ 600.000

years

• Activity cycle of ~ 50.000 years in

the last 350.000 years (Marra et al,

2002)

• Most recent products age <5.000

years (Funiciello et al., 2002)

• The most recent activities recorded

on the West side of the caldera

• Seismic recurrences of stronger

events ~ 60 years (Amato e

Chiarabba, 1995)

• Earthquakes depth between 2 and 5

km (Amato e Chiarabba, 1995)

27/04/2009 4TF Workshop, ESA Esrin


Since 1950 leveling campaigns measured significative ground uplift up to 30 cm.

GPS data are also available even though the only three monuments measuring a

displacement are in areas with no PS.

To retrieve the deformation field the PS-InSAR technique has been applied to an ERS

dataset from ascending and descending path covering 1992-2000.

PS-InSAR detected a deformation pattern with the highest rates of uplift

concentrated in the area of Albano, Ariccia and Nemi craters. Although these main

effects the whole deformation field is also characterized by further signals at

different scales.

To explain the possible causes of such results a model has been compared with PS-

InSAR pattern. The best model is located beneath the Albano crater, while the other

source is 3 km south of the older Ariccia crater.

Looking at the Colli Albani volcanic area


Image number Date Miss Pass Normal Baseline [m]

1 28/04/1993 ERS-1 Ascending 418.81

2 02/06/1993 ERS-1 Ascending -493.38

3 07/07/1993 ERS-1 Ascending -13.77

4 11/08/1993 ERS-1 Ascending -782.22

5 15/09/1993 ERS-1 Ascending -802.03

6 30/06/1995 ERS-1 Ascending 433.98

7 01/07/1995 ERS-1 Ascending 386.23

8 13/10/1995 ERS-1 Ascending -777.16

9 27/01/1996 ERS-2 Ascending -634.72

10 05/04/1995 ERS-1 Ascending -634.74

11 06/04/1996 ERS-2 Ascending -520.86

12 24/08/1996 ERS-2 Ascending -160.57

13 22/03/1997 ERS-2 Ascending -24.64

14 31/05/1997 ERS-2 Ascending -213.51

15 05/07/1997 ERS-2 Ascending -150.54

16 09/08/1997 ERS-2 Ascending 0.0

17 17/10/1997 ERS-1 Ascending -106.98

18 18/10/1997 ERS-2 Ascending -362.25

19 22/11/1997 ERS-2 Ascending -72.34

20 11/04/1998 ERS-2 Ascending 208.74

21 16/05/1998 ERS-2 Ascending 19.66

22 25/07/1998 ERS-2 Ascending -638.46

23 30/04/1999 ERS-1 Ascending -144.81

24 01/05/1999 ERS-2 Ascending -99.89

25 04/06/1999 ERS-1 Ascending -528.08

26 10/07/1999 ERS-2 Ascending 279.74

27 14/08/1999 ERS-2 Ascending -604.15

28 26/11/1999 ERS-1 Ascending 238.13

29 27/11/1999 ERS-2 Ascending 489.94

30 05/02/2000 ERS-2 Ascending -948.71

31 15/04/2000 ERS-2 Ascending 384.12

32 24/06/2000 ERS-2 Ascending -356.72

33 02/09/2000 ERS-2 Ascending -932.62

34 11/11/2000 ERS-2 Ascending 311.77

The SAR dataset and the PS-InSAR products (H-1)7 y

ears

of

acquis

itio

ns


Image number

Date Miss PassNormal Baseline

[m]

1 11/06/1992 ERS-1 Descending 250.76

2 16/07/1992 ERS-1 Descending -247.47

3 24/09/1992 ERS-1 Descending -223.54

4 29/10/1992 ERS-1 Descending 675.91

5 03/12/1992 ERS-1 Descending 196.88

6 07/01/1993 ERS-1 Descending -610.56

7 22/04/1993 ERS-1 Descending 678.21

8 01/07/1993 ERS-1 Descending -440.55

9 09/09/1993 ERS-1 Descending 625.72

10 18/11/1993 ERS-1 Descending 647.89

11 20/05/1995 ERS-1 Descending -215.95

12 24/06/1995 ERS-1 Descending -601.80

13 25/06/1995 ERS-2 Descending -724.91

14 03/09/1995 ERS-2 Descending -314.43

15 07/10/1995 ERS-1 Descending 387.43

16 08/10/1995 ERS-2 Descending 865.40

17 25/02/1996 ERS-2 Descending 807.95

18 30/03/1996 ERS-1 Descending -465.03

19 31/03/1996 ERS-2 Descending -570.17

20 04/05/1996 ERS-1 Descending 750.75

21 05/05/1996 ERS-2 Descending 667.12

22 09/06/1996 ERS-2 Descending -640.33

23 14/07/1996 ERS-2 Descending 314.83

24 18/08/1996 ERS-2 Descending -234.12

25 22/09/1996 ERS-2 Descending -22.88

26 27/10/1996 ERS-2 Descending 856.64

27 01/12/1996 ERS-2 Descending 842.26

28 05/01/1997 ERS-2 Descending -137.07

29 09/02/1997 ERS-2 Descending 360.06

30 16/03/1997 ERS-2 Descending 0.0

31 25/05/1997 ERS-2 Descending -97.48

32 03/08/1997 ERS-2 Descending -90.13

33 07/09/1997 ERS-2 Descending 415.42

34 11/10/1997 ERS-1 Descending 83.96

35 12/10/1997 ERS-2 Descending 311.69

36 16/11/1997 ERS-2 Descending 101.30

37 21/12/1997 ERS-2 Descending 33.54

38 25/01/1998 ERS-2 Descending -291.42

39 05/04/1998 ERS-2 Descending -541.66

40 10/05/1998 ERS-2 Descending 575.29

41 14/06/1998 ERS-2 Descending 854.91

42 19/07/1998 ERS-2 Descending -732.79

43 23/08/1998 ERS-2 Descending -339.12

44 27/09/1998 ERS-2 Descending 595.32

45 01/11/1998 ERS-2 Descending 774.68

46 06/12/1998 ERS-2 Descending -426.16

47 13/02/1999 ERS-1 Descending 1029.07

48 14/02/1999 ERS-2 Descending 823.05

49 20/03/1999 ERS-1 Descending 110.31

50 21/03/1999 ERS-2 Descending 46.10

51 25/04/1999 ERS-2 Descending -278.48

52 29/05/1999 ERS-1 Descending 742.79

53 30/05/1999 ERS-2 Descending 681.06

54 04/07/1999 ERS-2 Descending -179.37

55 08/08/1999 ERS-2 Descending 690.06

56 12/09/1999 ERS-2 Descending -744.93

57 16/10/1999 ERS-1 Descending 61.62

58 17/10/1999 ERS-2 Descending -265.08

59 21/11/1999 ERS-2 Descending -248.07

60 26/12/1999 ERS-2 Descending 338.05

61 29/01/2000 ERS-1 Descending -177.71

62 14/05/2000 ERS-2 Descending 920.49

63 18/06/2000 ERS-2 Descending -222.99

64 01/10/2000 ERS-2 Descending -514.00

65 05/11/2000 ERS-2 Descending 245.04

66 10/12/2000 ERS-2 Descending -414.82

8 years of acquisitions



Ascending Orbit Descending Orbit

SAR acquisition geometry over the test site

34 ERS1-2 data

28/04/93 - 11/11/00

n° PS: 280000

coherence >0.7



Ascending data

66 ERS1-2 data

11/06/92-19/12/00

n° PS: 240000

coherence >0.7



Descending data

Colli Albani

vertical velocity

map at 200 m

spaced grid



Colli Albani

EW velocity

map at 200 m

spaced grid




GPS measurements in

1995, 1996, 1997,

1998 do not show

significative

deformation except,

in 1995-96, when 2

cm subsidence has

been measured at

ING, CVA and VVR

(probably due to

shallow earthquakes

in 1995).

Later ING continuous

GPS is stable and can

be considered the

reference point and

PS have been

rescaled referred to it.

GPS and levelling (H-2)

17 levelling benchmarks are

available.

They were measured in two

campaings, IGM 1950 and

1997.

We selected 10 benchmarks

that are within the Asc and

Desc PS common area.


Average velocity levelling 1950 - 1997

vel

oci

ty (

mm

/y)


The maximum

uplift is detected in

Albano and Ariccia

villages (about 29

cm)

Average velocity levelling 1950 - 1997

vel

oci

ty (

mm

/y)

vel

oci

ty (

mm

/y)

Average velocity descending PS

Average velocity ascending PS

vel

oci

ty (

mm

/y)




Average velocity levelling 1950 - 1997vel

oci

ty (

mm

/y)

Vertical PS Velocity (mm/yr)

-0.5

0

0.5

1

1.5

2

2.5

3

20.0 25.0 30.0 35.0 40.0

vel

oci

ty (

mm

/y)




- The average velocity measured from levelling is obtained as

displacement/n° years. This clearly implies the hypothesis of constant rate

(1950-1997).

- The PS Asc and Desc velocity, so as the Vertical velocity, measure the

average displacement in the time interval 1992-2000.

- The different amount of average displacements can be explained as due

to a slowing phase of the phenomenon. At the moment, we have no further

measurements (GPS, levelling) enforcing such hypothesis.

Preliminary model (H-3)


Two Mogi point-pressure

sources have been used

aligned NS 7 km afar.

The N source is at 7 km

depth the S at 5 km.

The model is in general

agreement with

geophysical and

volcanological data

The EW PS map has been

used to provide further

constraints to the source

position.

Conclusions


The Colli Albani area has been investigated to detect possible surface

effects of deep volcanic and seismic activity.

Although the different time intervals we compared PS result 1992-2000,

leveling campaigns 1950-1997, GPS measurements.

In general, the model is in agreement with geophysical and

volcanological data.

The monitoring of the Colli Albani should provide a complete

assessment of the volcanic hazard in this area, strongly inhabited and

highly vulnerable.

New PS processing covering 2001-2009 would be necessary.

PS-InSAR analysis of Colli Albani volcanic area: … WS5...PS-InSAR analysis of Colli Albani...

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