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
IGARSS 2011 – 24-29 July, Vancouver, Canada
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
IGARSS 2011 – 24-29 July, Vancouver, Canada
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
IGARSS 2011 – 24-29 July, Vancouver, Canada
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.
IGARSS 2011 – 24-29 July, Vancouver, Canada
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
IGARSS 2011 – 24-29 July, Vancouver, Canada
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.
IGARSS 2011 – 24-29 July, Vancouver, Canada
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.
IGARSS 2011 – 24-29 July, Vancouver, Canada
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
IGARSS 2011 – 24-29 July, Vancouver, Canada
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)
IGARSS 2011 – 24-29 July, Vancouver, Canada
Mean Ground Velocity Maps (LoS)
Ascending Orbit Descending orbit
ERS+ENVISAT
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Time Series examples
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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.
IGARSS 2011 – 24-29 July, Vancouver, Canada
Up Component_+
LegendUp Velocity (mm/yr)
IGARSS 2011 – 24-29 July, Vancouver, Canada
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
IGARSS 2011 – 24-29 July, Vancouver, Canada
What ALOS can detect
2
1
1
N SS W E
2
2007-2010 1992-2010
IGARSS 2011 – 24-29 July, Vancouver, Canada
COSMO-SkyMed Ground Velocity map (LoS)
Ascending orbit
1
2
1
1
2 2
Area 11st of October, 2009:Mud landslide, 30 casualties
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The April 6, 2009 L’Aquila earthquakeCo-seismic &post-seismic phase
IGARSS 2011 – 24-29 July, Vancouver, Canada
Co-seismic deformation maps: first clear SAR interferogram (ENVISAT desc)
-27 cm LoS displacement
IGARSS 2011 – 24-29 July, Vancouver, Canada
Co-seismic deformation maps: second clear SAR interferogram (COSMO asc)
-25 cm LoS displacement
IGARSS 2011 – 24-29 July, Vancouver, Canada
Co-seismic deformation maps: vertical ground displacement
IGARSS 2011 – 24-29 July, Vancouver, Canada
Co-seismic deformation maps: East ground displacement
IGARSS 2011 – 24-29 July, Vancouver, Canada
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
IGARSS 2011 – 24-29 July, Vancouver, Canada
Descending PassAscending Pass26/02/2003- 14/07/2010 02/09/2003- 22/06/2010
ASAR Mean Velocity Map (LoS)
earthquake
IGARSS 2011 – 24-29 July, Vancouver, Canada
ALOS Mean Velocity Map (LoS)Track 639 Frame 830
Temporal span:15/01/2007-26/07/2010
Processed with SARscape
16 images
IGARSS 2011 – 24-29 July, Vancouver, Canada
Temporal span:29/04/2009-13/10/2009
23 slc usedAscending Orbit
COSMO-SkyMed Mean GroundVelocity Map (LoS)
Processed with SARscape
earthquakeearthquake
IGARSS 2011 – 24-29 July, Vancouver, Canada
COSMO-SkyMed Displacement Map (LoS)
IGARSS 2011 – 24-29 July, Vancouver, Canada
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.
IGARSS 2011 – 24-29 July, Vancouver, Canada
Thank youfor your attention!