Deep-seated Gravitational Slope Deformation (DGSD) triggered by the 2009 L’Aquila earthquake detected by X-band DInSAR
M. Chini1, M. Moro1, M. Saroli2, S. Stramondo1, C. A. Brunori1 and S. Salvi1
1 Istituto Nazionale di Geofisica e Vulcanologia
Advances in the Science and Applications of SAR Interferometry
ESA ESRIN30th November - 4th December 2009Frascati, Italy
2 University of Cassino
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
Outline
• Dataset: COSMO-SkyMed X-Band SAR
• Deep-seated Gravitational Slope Deformation (DGSD): characteristics
• April 6th, 2009, L’ Aquila earthquake
• Results
• Conclusions
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
- COSMO-SkyMed is a constellation of 4 satellites (three already in orbit) developed by the Italian Space Agency.
- COSMO is aimed to provide fast, metric resolution all-weather imagery for disaster management. It hosts a flexible multi-mode X-band Synthetic Aperture Radar (SAR), with right and left-looking imaging capabilities, incidence angle range 20°-60°, and 12 hours minimum revisit time (full constellation).
- The first ever seismological application of COSMO DInSAR is the May 12, 2008, Sichuan (China) earthquake.
COSMO-SkyMed X-Band SAR
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
Deep-seated Gravitational Slope Deformation (DGSD): characteristics
• Involved mass volume (of about hundreds m3);
• Width and length extension (few kilometers);
• Thickness (from about 60 m up to hundreds of meters);
• Movement rates (from few millimeters per year up to few centimeters per year);
• The mechanical and dynamic behavior is affected by gravitational creep phenomena.
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
shear contraction zone
• Sackung or rock flow
Sliding planes are not always recognizable
• Lateral spreadIt is due to rocks with a fragile behavior superimposed on a more plastic bedrock
• Block slideSliding planes (preexistent or new) are well defined
DGSD typology
• Sagging of Mountain slopes (Hutchinson, 1988). Comparable to Sackung phenomena by Zischinski.
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
Morphological characteristics
• Double ridges
• Linear and bent depressions (natural trenches)
• Scarps and counterscarps
• Bulging lower slopes
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
April 6th, 2009, L’Aquila earthquake
A Mw 6.3 earthquake occurred on April 6th, 2009 (01:32 GMT) few km from L’Aquila city.
The seism hit a densely populated region of the Apennines and was felt all over Central Italy.
The earthquake has been imaged by COSMO-SkyMed that acquired a number of data thanks to the request of the Department of Civil Protection to ASI.
06/4/2009
07/4/2009
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
Co-seismic deformation pattern
Colle Clinelle
Colle Campetello
COSMO-SkyMed
dataset acquisition:
04/04/2009
12/04/2009
Geometric resolution: 5m
Perpendicular baseline: 430m
Look angle: 35°
1 color cycle = 1.5 cm LOS
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
Colle Campetello sackung
The entire deformation is located in the major trench zonesIt is up to 4-5 cm
Colle Campetello
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
Major trench zone
“Colle Campetello” sackung 3D view
A
BA B
B
A
Major trench zone
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
Colle Campetello Main trench
OpeningOpeningOpeningOpeningOpeningOpening
trench
trenchOpeningOpeningOpening
OpeningOpeningOpening
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
“Colle Clinelle” sagging
The entire deformation is located in the major trench zonesIt is about 3 cm
A BC
AB
C
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
The B portion of the profile corresponds with the main trench zone and a prevalent vertical movement is expected.
The C portion of the profile is less steep. It is in agreement with the sagging model where part of the DGSD is laterally moving.
A
B
C0
-2
-3
cm
-1
“Colle Clinelle” deformation profile
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
“Colle Clinelle” sagging 3D view
AB
C
Major trench zone
Front of DGSD.Zone of major lateral movement
Zone of major vertical movement
A BC
Major trench zone
Advances in the Science and Applications of SAR Interferometry ESA ESRIN, 30th November - 4th December 2009 Frascati, Italy
Conclusions
The HR SAR of COSMO- SkyMed (and DInSAR outcomes) and photogeological analysis allowed us to verify the seismic triggering of DGSD for the L’Aquila earthquake.
The observed deformations are co-seismic only, since no movements have been detected in the post-seismic interferograms.
The measured deformation varies from 3 up to 5 cm for Colle Clinelle and Colle Campetello, respectively.
The study demonstrate that the Mw 6.3 L’Aquila earthquake induced a ground shaking large enough to trigger pre-existing DGSDs.
Bigger earthquakes may reactivate a larger number of DGSD, it seems to be a reliable hypothesis, leading to increase the likelihood of a catastrophic collapse.
