SBAS-DInSAR time series in the last eighteen years at Mt. Etna volcano (Italy)
G. SOLARO 1 , F. CASU 1 , L. PAGLIA 1 , A. PEPE 1 , S. PEPE 1 , E. SANSOSTI 1 , P. TIZZANI 1 , R. LANARI 1
1. IREA – CNR, Naples (Italy)
Summary We investigate deformation phenomena affecting Mt. Etna by exploiting the Small BAseline Subset (SBAS) technique that permits to produce mean deformation maps and time series relevant to large areas obtained by using relatively low resolution DInSAR interferograms . We present first preliminary COSMO-SkyMed results (2009-2010 time interval) in term of spatial and temporal deformation . W e benefit from the availability of ERS-ENVISAT multi-orbit (ascending and descending) data in order to discriminate the vertical and East-West components of the volcano edifice displacements and generate the relevant time series.
SBAS-DInSAR algorithm: key aspects To produce deformation times-series from a SAR dataset, the SBAS approach:
properly “links” the interferometric SAR data subset (if present) separated by large baselines (the SVD method is applied).
exploits interferograms characterized by a “small baseline” in order to mitigate decorrelation phenomena;
“ merging” SAR data acquired by different sensors with the same illumination geometry, as for the case of ERS-1/2 and ENVISAT IS2 .
≈ 1 - 2 mm/year on the mean deformation velocity
≈ 5 - 10 mm on the single displacement
ERS ERS ERS ERS ERS ENVISAT ENVISAT
Two scale SBAS approach Multi-look Interferogram Low resolution detects the ground deformation ,particularly those related to volcanoes Low Spatial resolution processing Resolution 100x100m Single-look Interferogram Resolution 5x20m Full resolution is useful to detect and follow the deformation of localized structures Full Spatial resolution processing
1992- 2006 Vertical/East-West ERS - ENVISAT mean velocities for Etna Vertical East-West Neri et al. 2009, GRL [mm/yr] > 15 <-15 Down Up [mm/yr] > 20 <-20 West East
We use two different strategies analysis Cumulative displacements and deformation time series analysis 2000-2003 time interval = non-linear deformation 1994-2000 and 2003-2008 time interval = linear trend of deformation deformation velocity analysis Our goal is to provide an interplay between surface volcano deformation and volcanic activity
Etna SAR Velocity maps We analysed the 1994-2000 and 2003-2008 time interval because of their linear behaviour of deformation trend
Eastern flank velocity profiles analysis There is a general correspondence between the discontinuities in velocity and active faults confirming that the known faults are active during 1994-2008
Eastern flank histograms velocity analysis Sectors 2,6,7 and 8 show narrower histograms with a clear peak indicating a homogeneous ew velocity and a rigid behaviour of that block
Weastern flank velocity profiles analysis This flank conists of three main blocks
Weastern flank histograms velocity analysis Sectors 9 and 10 are in part kinematically distinct both moving toward west
Three main processes affecting the observed volcano deformation Solaro et al. (2010) Journal of Geophysical Research vol. 115, B10405, 2010.
COSMO-SkyMed results Mean deformation velocity map Orbit:descending Band X ( = 3.1 cm) Resolution: 25x25m Time interval: July 2009 – December 2010 Mean velocity [cm/yr] > 5 <-5 COSMO-SkyMed: 8 days ENVISAT: 35 days
COSMO-SkyMed results Mean deformation velocity map Orbit:descending Band X ( = 3.1 cm) Resolution: 25x25m Time interval: July 2009 – December 2010 Mean velocity [cm/yr] > 5 <-5 Pernicana Fault
Direzione di vista Direzione di volo Atmospheric noise 30/03/2010 - 07/04/2010; spatial baseline : 133 m M=3.6 eqk occurred on April 3rd 2010
COSMO-SkyMed – ENVISAT comparison COSMO-SkyMed ENVISAT Revisiting time: 8 days Period: July 2009 – December 2010 Band X ( = 3.1 cm) Resolution: 25 x 25 meters Revisiting time : 35 days Period: 1992 – 2010 Band C ( = 5.6 cm) Resolution: 90 x 90 meters
Confronto COSMO-SkyMed - ENVISAT: Etna Revisiting time: 35 days Period: 1992 – 2010 Band C ( = 5.6 cm) Resolution: 90 x 90 meters COSMO-SkyMed ENVISAT Revisiting time: 8 days Period: July 2009 – December 2010 Band X ( = 3.1 cm) Resolution: 25 x 25 metri
COSMO-SkyMed – ENVISAT comparison COSMO-SkyMed ENVISAT M=3.6 eqk occurred on April 3rd 2010
CSK notes It is clearly visible how the 8 (and 4)-days COSMO-SkyMed repeat pass permits to better detect and model the ongoing deformation with respect to the 35-days ENVISAT data. Indeed, for instance, we can appreciate the jump due to the M=3.6 April 3 rd , 2010 earthquake It is evident the increased spatial density of the COSMO-SkyMed measurements with respect to the ENVISAT ones Using of X-band data sensor for volcano monitoring and Civil Protection purposes