Maya ILIEVA1,2,3, Rana CHARARA1,3, Pierre BRIOLE3

1 University “Pierre and Marie Curie” Paris – 6, France2 Bulgarian Academy of sciences, Laboratory of geodesy, Sofia, Bulgaria

3 École Normale Supérieure, Laboratory of geology, Paris, France

Maya ILIEVA1,2,3, Rana CHARARA1,3, Pierre BRIOLE3

1 University “Pierre and Marie Curie” Paris – 6, France2 Bulgarian Academy of sciences, Laboratory of geodesy, Sofia, Bulgaria

3 École Normale Supérieure, Laboratory of geology, Paris, France

IntroductionIntroduction

In the area of Eastern Mediterranean the African plate goes under the Eurasia plate and the latter collides with the Apulian plate. The studied zone is also determined as a complex junction of several more tectonics blocks which drift in different directions and with different velocities.

The investigation covers the Gulf of Patras and Central Ionian Islands. The area of Patras is a transition zone between the Corinth rift and the northwestern end of the Hellenic arc, while in the area of the Central Ionian Islands the transition zone between the West Hellenic arc and the Apulian plate is recognized as Kephalonia Fault Zone (KFZ) with strike-slip faulting.

For the study of the Lefkada earthquake, from the available 13 ascending (Asc) and 20 descending (Desc) ENVISAT images, 7 Asc and 9 Desc, respectively, were used. There is one image before the earthquake for both groups in this set. 21 Asc and 36 Desc interferograms were processed with ROI_PAC software Version 3. This data set was used to generate Maps of coherence. On the base of the known fault parameters, synthetic models for expected interferograms were created.

ReferencesReferences

ANALYSIS OF THE DEFORMATIONS OF WESTERN CORINTH RIFT BY SATELLITE GEODESY

Seismicity and Fault systemSeismicity and Fault system

KFZ and the northwestern part of the WHA are the seismically most active region of Greece. One of the most significant recent events (M = 6.3) in the studied area occurred on August 14, 2003 northwest of the Lefkada island. The maximum intensity has been evaluated as Io = VII+ to VIII in the town of Lefkada (Pavlides et al., 2004).

Studied areas are characterized by high seismicity and natural hazard potential. There is serious seismic risk not only for the city of Patras, which is one of the biggest cities in Greece, but also for the neighbouring towns and villages.

Fig.1. Sachpazi et al. (2000)

InSARInSARGPS measurementsGPS measurements

Avallone A., P. Briole, A.M. Agatza-Balodimou, H. Billiris, O. Charade, C. Mitsakaki, A. Nercessian, K. Papazissi, D. Paradissis, G. Veis (2004). Analysis of eleven years of deformation measured by GPS in the Corinth Rift Laboratory area, special issue of the C.R. Acad. Sci, 336, 301-311.Briole P., A. Rigo, H. Lyon-Caen, J.-C. Ruegg, K. Papazissi, C. Mitsakaki, A.M. Balodimou, G. Veis, D. Hatzfeld, A. Deschamps (2000). Active Deformation of the Corinth Rift, Greece: Results from repeated GPS surveys between 1990 and 1995, J. Geophys. Res, 25605-25625.Nyst, M., and W. Thatcher (2004), New constraints on the active tectonic deformation of the Aegean, J. Geophys. Res., 109, B11406Hollenstein C, A. Geiger, H.G. Kahle, G. Veis ( 2006). CGPS time-series and trajectories of crustal motion along the West Hellenic Arc, Geophys. J. Int., 164, 182-191.Hollenstein Ch., M.D. Müller, A.Geiger, H.-G. Kahle (2008). GPS-Derived Coseismic Displacements Associated with the 2001 Skyros and 2003 Lefkada Earthquakes in Greece. Bulletin of the Seismological Society of America, Vol. 98, No. 1, pp. 149-161.Sachpazi M., A. Hirn, C. Clément, F. Haslinger, M. Laigle, E. Kissling, P. Charvis, Y. Hello, J.-C. Lépine, M. Sapin, J. Ansorge (2000). Western Hellenic subduction and Cephalonia Transorm: local earthquakes and plate transport and strain. Tectonophysics, 319, 301-319.Pavlides S.B., G.A. Papadopoulos, A. Ganas, G. Papathanassiou, V. Karastathis, D. Keramydas, A. Fokaefs (2004). The 14 August 2003 Lefkada (Ionian sea) earthquake. 5 th International Symposium on Eastern Mediterranean Geology, Tessaloniki, Greece, 14-20 April 2004.http://www.openchannelfoundation.org/projects/ROI_PAC

Fig.10. Differential Asc Interferogram030321-041105

Fig.13. Differential Desc Interferogram030625-040714

Fig.11. Map of coherence from 21 Asc interferograms

Fig.14. Map of coherence from 36 Desc interferograms

AcknowledgementsAcknowledgements

We would like to thank Panagiotis Elias, Aurore Franco, Antonios Mouratidis for their invaluable help.

Fig.2 Fig.3

Fig.4

Two GPS campaigns were carried out in 2003 and 2006, All data were processed using GAMIT software Version 10.7 and the same processing strategies. We used precise orbits and GPS data from ten surrounding IGS stations to tie our network to ITRF2000.

Only the horizontal solutions are presented here and also some vectors from others grouped by Nyst (Nyst et al. 2003) that show that the average uncertainties of the velocity vectors are in the order of ± 30 mm/yr.

The difference between the velocity of point PRSL and the other points define the Western Block of Central Greece, in which they show that the northern limit of the block is located to the north of Trichonis Lake.

The residual of the velocity field after a block rotation of 5+0.5˚/Myr till zero velocity for PRSL is presented. In “Europe fixed”, the Rotation Pole is located at 21.12˚E, 39.09˚N (Avallone et al. 2004).

Fig.5

Fig.8 Fig.9

Fig.6. The 14 August 2008 Lefkada earthquake and the aftershocks

Fig.12. Synthetic Asc Interferogram

Fig.15. Synthetic Desc Interferogram

Fig.7. Coulomb stress distribution after the Lefkada earthquake