C.Tolomei , S. Atzori, J. P.Merryman, G. Pezzo, S. Salvi (1)

IGARSS 2011 – 24-29 July, Vancouver, Canada

Investigating the seismic cycle in Italy by multitemporal analysis of

ALOS, COSMO-SkyMed and ERS/Envisat DInSAR data sets

C.Tolomei, S. Atzori, J. P.Merryman, G. Pezzo, S. Salvi (1)

(1) Istituto Nazionale di Geofisica e Vulcanologia - Rome, italy


Outline

1. The SIGRIS Project (funded by Italian Space Agency):exploiting Earth Observation data for seismic risk management

2. SAR data processed and DInSAR techniques used

3. The Straits of Messina and the L’Aquila cases

4. Conclusions

Further information: www.sigris.it


Two operations mode

To generate EO-based, value-added products for the operational use by the National Civil Protection Service in two risk management phases:

1. Knowledge & Prevention, i.e. support to the Seismic Hazard assessment

2. Warning & Crisis, i.e. support to the Emergency management

1. During normal routine operations, the products for the Knowledge & Prevention (i.e. support to Seismic Hazard Assessment), are generated

2. During a seismic Crisis, activated by the INGV surveillance system (SISMAP) for earthquakes > M5.5, products are generated in near-real time, in incremental versions

To identify factors limiting the EO data exploitation


What we produceGround velocity maps at the fault scale

The SIGRIS PR1 products are maps showing the small (mm/yr) progressive movements of the Earth’s surface occurred over a period of years.

We use them to quantify the crustal deformation associated to the seismic cycle, in particular in the inter-seismic and post-seismic phases.

The amount and patterns of crustal deformation are related to the tectonic stress accumulated and then released during the earthquakes.


What data we useSAR data

•Same viewing geometry (interferometric acquisitions)•From ascending and descending passes•Consistent datasets (15-20 images minimum) •Minimum acquisition frequency: 2 months for L-band, 1 month for C-band, 10

days for X-band (note: some images can be discarded during processing)

CGPS data

• Site displacement time series for the 3 cartesian components• Minimum 3 stations per SAR coverage for a correct SAR-GPS integration• To estimate and remove possible ramps

X-Band: Cosmo-SkyMed (April, 2009 ->), asc-desc C-Band: ERS1/2 (1992-2001), asc-desc ENVISAT (2003-2010), asc-desc L-Band: ALOS (2007->), asc


DInSAR techniques

We use multitemporal InSAR techniques:SBAS-Small BAseline Subset (IREA-CNR), SARscape (Sarmap);

Permanent Scatterers (T.R.E.,Milano).

We validate the result using:CGPS levelling lines

Geological and seismological data.

• Bernardino P. et al., 2002, A new algorithm for surface deformation monitoring based on Small Baseline Differential SAR Interferograms. IEEE Trans on Geosci. and Remote Sensing, 40.

• Ferretti, A., C. Prati, and F. Rocca (2001), Permanent scatterers in SAR interferometry, IEEE Trans. Geosci. Remote Sens., 39(1), 8– 20.


SIGRIS Test Sites

The SIGRIS Project considers 4 test areas in Italy.

We processed over 1100 SAR images from ERS, ENVISAT, ALOS, and COSMO-SkyMed satellites.

We generated, validated, and delivered to the Italian Civil Protection over 100 PR1 product items.


The Straits of Messina

The largest earthquake of the XX century in Italy Mw = 7.1, in 1908

Debated earthquake source (at least 5 different fault models)

To be crossed by a 4-km long suspended bridge

From Amoruso et al, 2002, JGR

Inter-seismic phase


Ground deformation using time-series DInSAR

SAR Data:

ERS (1992-2001)

71 images (D), 37 (A)

ENVISAT (2003-2008)34 images (A)

ALOS (2007-2010)

22 images (A)

COSMO-Skymed (2009-2010)17 images (D)


Mean Ground Velocity Maps (LoS)

Ascending Orbit Descending orbit

ERS+ENVISAT


Time Series examples


Up & East Velocity Maps

Up Component East Component

• look angle = variable along the swath • We constrained the SAR North component based on the CGPS one.


Up Component_+

LegendUp Velocity (mm/yr)


East Component

4 mm/yr

0 mm/yr

-5 mm/yr

-1 mm/yr

-4 mm/yr

-9 mm/yr

LegendEast Velocity (mm/yr)

IGARSS 2011 – 24-29 July, Vancouver, Canada Temporal span: 10/01/07- 05/06/10 22 images

ALOS Mean Ground Velocity Map (LoS)

Processed with SARscape


What ALOS can detect

2

1

1

N SS W E

2

2007-2010 1992-2010


COSMO-SkyMed Ground Velocity map (LoS)

Ascending orbit

1

2

1

1

2 2

Area 11st of October, 2009:Mud landslide, 30 casualties


The April 6, 2009 L’Aquila earthquakeCo-seismic &post-seismic phase


Co-seismic deformation maps: first clear SAR interferogram (ENVISAT desc)

-27 cm LoS displacement


Co-seismic deformation maps: second clear SAR interferogram (COSMO asc)

-25 cm LoS displacement


Co-seismic deformation maps: vertical ground displacement


Co-seismic deformation maps: East ground displacement


The L’Aquila case

Descending Orbit

• 52 images (Envisat)• From February,2003

to July, 2010• 135 interferograms

Ascending Orbit

• 34 images (Envisat)• From September, 2003

to June, 2010 • 91 interferograms


Descending PassAscending Pass26/02/2003- 14/07/2010 02/09/2003- 22/06/2010

ASAR Mean Velocity Map (LoS)

earthquake


ALOS Mean Velocity Map (LoS)Track 639 Frame 830

Temporal span:15/01/2007-26/07/2010


16 images


Temporal span:29/04/2009-13/10/2009

23 slc usedAscending Orbit

COSMO-SkyMed Mean GroundVelocity Map (LoS)


earthquakeearthquake


COSMO-SkyMed Displacement Map (LoS)


Conclusions Multitemporal InSAR techniques are able to measure the ground deformation

related to the seismic cycle, down to 1 mm/yr (inter-seismic phase); In our setting we find that, for the measurements of low-level inter-seismic

deformation, the C Band is the best suited, while the X Band is too subject to temporal decorrelation, and the L band lacks sensitivity;

The post-seismic trends are best measured using X band data (higher resolution);

All SAR systems used are well suited for co-seismic deformation mapping, although shorter revisit intervals (2-3 days) are needed for fully operational applications;

Continuity of data acquisition and archival is needed to effectively measure the long-term deformation associated to the seismic cycle;

Using images from different sensors (C, L, X band) in a synergistic way, allows cross-validation and more significant results.

Acknowledgements: Dr. Paolo Riccardi, Dr. Alessio Cantone (SARMAP); Dr. Simona Zoffoli, Italian Space Agency.


Thank youfor your attention!

C.Tolomei , S. Atzori, J. P.Merryman, G. Pezzo, S. Salvi (1)

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