The April 6 th 2009, L Aquila (Italy) earthquake: DInSAR analysis and seismic source model inversion

Transcription

1 ESA ESRIN 30th November - 4th December 2009 Frascati, Italy The April 6 th 2009, L Aquila (Italy) earthquake: DInSAR analysis and seismic source model inversion Simone Atzori, Christian Bignami, Marco Chini, Christodoulos Kyriakopoulos, Salvatore Stramondo, Cristiano Tolomei, Elisa Trasatti and Stefano Salvi Istituto Nazionale di Geofisica e Vulcanologia

2 L Aquila EQ context 2/19

3 27 apr jul 2008 DInSAR pairs 11 mar apr apr apr apr 2009 Envisat Asc Envisat Dsc COSMO SkyMed Asc ALOS Asc Images processed with SARscape Topography subtracted with a 5-m DTM (from Airborne SAR) Linear trends removed with GPS (permanent stations) 3/19

4 Envisat ASC (C-band) (11/03/09-15/04/09) GPS stations 4/19

5 Envisat DSC (C-band) (27/04/08-12/04/09) 5/19

6 ALOS PALSAR (L-band) (20/07/08-22/04/09) 113 km 70 km 6/19

7 COSMO SkyMed Asc (X-band) (04/04/09-12/04/09) 45 km Among its strength points are its flexibility (it can operate in three different modalities, routine, crisis or emergency) and its short revisit time from ASI website 7/19

8 GPS stations Five new stations were added 5 days before the main event* * Anzidei et al., Coseismic deformation of the destructive April 6, 2009 L Aquila earthquake (central Italy) from GPS data, GRL (36), L17307, doi: /2009gl039145, /19

9 Modeling Non-linear inversion (fault geometries) with analytical homogeneneous elastic model (Okada). Linear inversion (slip distribution) with analytical homogeneous elastic model. Linear inversion with analytical layered elastic model (Wang). Linear inversion with Finite Element model CFF analysis (stress transfer over surrounding faults). Non-linear joint inversion of geodetic and seismological (teleseismic) data 9/19

10 Subsampling 10/19

11 Geodetic Model and seismicity From non-linear inversion of DInSAR and GPS data: Length (km) in [10-20] Width (km) in [5-15] Depth (km) in [0-8] Strike angle ( ) in [ ] Dip angle 50.0 ( ) fixed Fault east (km) in [ ] Fault north (km) in [ ] Rake angle ( ) in [ ] Slip 0.51 (m) in [0-15] Aftershocks relocated with double difference technique (and 1-D velocity model)*. * from Chiaraluce et al., 2009 [in prep.] 11/19

12 Numerical fault modelling We use Finite Element Methods to define a more realistic model of the crustal structure, including: surface topography medium anisotropy vertical and lateral discontinuities Masterlark D seismic tomography by De Gori and Chiarabba [in prep.] 12/19

13 Complex geological structure The tomography evidences a lateral and vertical heterogeneous elastic structure Vp, Vs velocities transformed into elastic parameters (rigidity, Poisson coeff.) Tomography cross sections 13/19

14 FE heterogeneous model Slip distribution Results Maximum Slip 0.9 m Mean Rake -90 Misfit 4.1 M geod Nm M w = 6.1 Resolution matrix Method Slip (m) 14/19

15 Slip distribution and structure on fault Slip distribution Shear modulus The coseismic slip is distributed along the strike direction, in an area of low seismicity; Slip is concentrated between 5-8 km depths; Slip is inhibited at greater depths because of the high rigidity values. 15/19

16 Postseismic COSMO Asc Envisat Dsc Envisat Asc ALOS Galvani A. et al, DEFORMAZIONE INTER E POSTSISMICA DA DATI GPS DEL BACINO DELL'AQUILA, 28 Convegno Nazionale GNGTS, sessione 1.2, Novembre /19

17 COSMO acquisitions from 6/4 to 22/4 Satellite Date & Time Mode Beam Polar. Looking side Satellite Date & Time Mode Beam Polar. Looking side S1 6/4/ HI 0B VV RD S3 14/4/ HI 15 HH RD S 1 7/4/ HI 5 HH L A S 2 14/4/ HI 0B VV RD S 3 8/4/ HI 14 HH R A s2 15/4/ HI 5 HH LA S3 8/4/ HI 24 VV RD S1 15/4/ HI 14 HH RA S2 8/4/ H I 9 H H R D S 1 1 5/4/ HI 24 VV RD S1 8/4/ S 2 15 HH LD S3 15/4/ HI 0B VV RD S 2 9/4/ HI 15 HH L A S 3 16/4/ S 2 9 HH LA S 1 9/4/ S 2 7 HH R A S 1 16/4/ HI 9 HH RD S3 9/4/ HI 10 HH RD S2 16/4/ S 2 14 HH LD S3 10/4/ HI 15 HH L A S 1 17/4/ HI 15 HH LA S2 10/4/ S 2 0D HH L A S 2 17/4/ S 2 7 HH RA S1 10/4/ HI 18 HH R A S 3 17/4/ S 2 15 HH LD S1 10/4/ HI 19 VV RD S2 18/4/ HI 18 HH RA S2 10/4/ HI 0B HH LD S2 18/4/ HI 19 VV RD S1 11/4/ HI 23 HH L A S 1 18/4/ HI 0B HH LD S3 11/4/ S 2 0D HH L A S 3 19/4/ HI 18 HH RA S1 11/4/ HI 5 HH RD S2 19/4/ HI 23 HH LA S3 11/4/ HI 0B HH LD S3 19/4/ HI 19 VV RD S1 12/4/ HI 11 HH L A S 2 19/4/ HI 5 VV RD S2 12/4/ HI 9 HH R A S 3 20/4/ HI 5 VV RD S3 12/4/ HI 14 HH LD S2 20/4/ HI 11 HH LA S3 13/4/ HI 9 HH R A S 1 20/4/ HI 9 HH RA S2 13/4/ S 2 33 HH R A S 3 21/4/ HI 11 HH LA S2 13/4/ HI 15 HH RD S1 21/4/ HI 15 HH RD S1 14/4/ HI 0A HH R A S 2 22/4/ HI 19 HH LD S3 14/4/ S 2 33 HH R A S 1 22/4/ HI 0B VV RD 17/19

18 Conclusions COSMO SkyMed and Envisat provided useful information for the onfield survey teams during the emergency, defining the exact location of the active fault. ALOS passed too late but can contain info about postseismic displacement. Two completely independent datasets (from geodesy and seismology) defined with high precision the location and orientation of the Paganica fault. The tomography evidences lateral and vertical elastic heterogeneities, with a potential effect on coseismic slip distribution. The coseismic slip is distributed along the strike direction, in an area of low seismicity. Slip is concentrated between 5-8 km depths and it is inhibited at greater depths because of the high rigidity values. Most of the posteismic signal happens in few days after the EQ; COSMO SkyMed shown its high flexibility, unfortunately (apparently) not oriented to DInSAR analysis. Precise integration of DInSAR and GPS allows the detection of low frequency displacement components. 18/19

19 Thank you! 19/19

20 Thank you! Public research in Italy is experiencing one the worse period ever; please be sure to support our new campaign: 20/19