HR: 0800h
AN: T51A-0307    [Abstracts]
TI: New Developments in the Study of Seismicity and Crustal Structure in the Western Hellenic arc
AU: * Papoulia, J E
EM: nana@ath.hcmr.gr
AF: Hellenic Center for Marine Research, Institute of Oceanography, 46,7 Km Athinon Souniou Ave., Athens, 19013, Greece
AU: Makris, J
EM: info@geopro.com
AF: GEOPRO GmbH, St. Annenufer 2, Hamburg, 20457, Germany
AU: Papadopoulos, G
EM: papadop@gein.noa.gr
AF: National Observatory of Athens, Geodynamic Institute, Lofos Nymfon, Thissio, Athens, 11810, Greece
AU: Nicolich, R
EM: r.nicolich@univ.trieste.it
AF: University of Trieste, Department of Civil Engineering, Via A. Valerio 10, Trieste, 34127, Italy
AU: Tsambas, A
EM: tsambas_a@yahoo.gr
AF: Hellenic Center for Marine Research, Institute of Oceanography, 46,7 Km Athinon Souniou Ave., Athens, 19013, Greece
AU: Ilinski, D
EM: info@geopro.com
AF: National Observatory of Athens, Geodynamic Institute, Lofos Nymfon, Thissio, Athens, 11810, Greece
AB: The western part of the Hellenic Arc between Pyrgos and Pylos, western Peloponnese, is one of the most seismically active areas in the whole Mediterranean. This area has been repeatedly affected by large magnitude earthquakes that have caused severe destruction and human loss (i.e. 1886 Philiatra M7.3, 1893 Zante-Keri M6.5, 1899 Kiparissia M6.5, 1947 Pylos M7.0, and 1997 Gargaliani M6.6). Some of the largest regional tsunamis in the Mediterranean Sea have also been observed in association with large earthquakes (i.e. 1630 and 1866, south-western Hellenic Arc), affecting near field as well as remote coastal segments in western Peloponnese, Crete, and as far as Alexandria (Egypt), Adriatic Sea and east Sicily. This situation requires urgent solutions for an effective risk management and mitigation plan. For this, it is essential to study the local seismic activity and define the active fault zones on/ and offshore with high accuracy and resolution required for a reliable seismic and tsunami hazard assessment. In the present study, we built a combined on/offshore seismic array consisting of 17 4C Ocean bottom Seismographs (OBS) and 15 land-stations with three 4.5-Hertz geophones in each locality, and recorded the seismic activity for a period of 2 months. We located more than 3,500 earthquakes by using minimum of 6 stations, and applied a local velocity model that was obtained from active seismic experiments. The microseismicity map is associated with the active fault zones in the area. The shallow activity (0-15 Km depth) shows the deformation of the sediments and the upper crust. It is mainly concentrated around Zakynthos island and the offshore zone of Pylos. Seismicity associated with the deeper part of the crust (16 - 30 Km) coincides again with the tectonically uplifted block of Pylos, Messinia and also with the deformation below the island of Zakynthos. Deeper seismicity follows the subduction zone below western Peloponnese with constantly increasing depth towards the western and eastern parts of it. In a specific zone associated with the transtensional basin between Zakynthos and Pylos, the seismicity extends to depths more than 80 Km. This deep activity is associated with a major fault zone that is displacing vertically two different crustal units of the western Hellenic collision zone. Focal mechanisms associated with this fault zone demonstrate mainly dextral strike slip movements. The active seismic experiments that mapped the geometry of the sediments and crust clearly show that the internal Hellenic zones are thrusted over the external ones and the uplifted units exposed on the island of Zakynthos and that of Messinia are highly elevated blocks of the thrust belts. The present paper is a contribution to the EC, FP6 FrameWork, SEAHELLARC project no. 037004.
DE: 8100 TECTONOPHYSICS
DE: 8164 Stresses: crust and lithosphere
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting