HR: 11:05h
AN: S52A-04    [Abstracts]
TI: Seismic Structure and Activity of the North Anatolian Fault in the Sea of Marmara From the SEISMARMARA Leg1 Seismic Survey
AU: * Becel, A
EM: becel@ipgp.jussieu.fr
AF: Sismologie Experimentale, Institut de Physique du Globe de Paris, Case 89, 4 Place Jussieu, Paris Cedex 05, 75252 France
AU: Charvis, P
EM: charvis@obl-vlfr.fr
AF: IRD-Geosciences Azur, Quai de la Darse, Villefranche sur Mer, 06230 France
AU: de Voogd, B
EM: beatrice.devoogd@univ-pau.fr
AF: Departement des Sciences de la Terre, Universit‚ de Pau, Pau, 64012 France
AU: Galve, A
EM: galve@ipgp.jussieu.fr
AF: Sismologie Experimentale, Institut de Physique du Globe de Paris, Case 89, 4 Place Jussieu, Paris Cedex 05, 75252 France
AU: Hirn, A
EM: hirn@ ipgp.jussieu.fr
AF: Sismologie Experimentale, Institut de Physique du Globe de Paris, Case 89, 4 Place Jussieu, Paris Cedex 05, 75252 France
AU: laigle, m
EM: laigle@ipgp.jussieu.fr
AF: Sismologie Experimentale, Institut de Physique du Globe de Paris, Case 89, 4 Place Jussieu, Paris Cedex 05, 75252 France
AU: Lepine, J
EM: lepine@ ipgp.jussieu.fr
AF: Sismologie Experimentale, Institut de Physique du Globe de Paris, Case 89, 4 Place Jussieu, Paris Cedex 05, 75252 France
AU: Murai, Y
EM: murai@eos.hokudai.ac.jp
AF: Institute of Seismology and Volcanology, N10-W8, Sapporo, 060-0810 Japan
AU: Ozalaybey, S
EM: Serdar.Ozalaybey@posta.mam.gov.tr
AF: TUBITAK-MAM Marmara Research Center, Gebze, Kocaeli, 41470 Turkey
AU: Sapin, M
EM: sapin@ipgp.jussieu.fr
AF: Sismologie Experimentale, Institut de Physique du Globe de Paris, Case 89, 4 Place Jussieu, Paris Cedex 05, 75252 France
AU: Shimamura, H
EM: shima@eos.hokudai.ac.jp
AF: Institute of Seismology and Volcanology, N10-W8, Sapporo, 060-0810 Japan
AU: Singh, S
EM: singh@ipgp.jussieu.fr
AF: Geosciences Marines, Institut de Physique du Globe de Paris, Case 89, 4 Place Jussieu, Paris Cedex 05, 75252 France
AU: Taymaz, T
EM: taymaz@itu.edu.tr
AF: ITU, Istanbul Technical University, Maslak, Istanbul, 80626 Turkey
AB: The Sea of Marmara is the continuation to the West of the North Anatolian Fault (NAF) that produced the two destructive earthquakes of Izmit and Duzce in 1999 just to its East. It is prone to future major earthquakes as it has experienced in the past and is a present seismic gap. In 2001, the SEISMARMARA project was carried out in the whole North Marmara Trough with the aim to improve the knowledge of the regional tectonics and the evolution at crustal scale by imaging faults, basins and deep geological features by their structure. This experiment was a multi-method approach combining regional scale multichannel seismic profiles (MCS), refraction and wide-angle reflection towards OBS and land stations as well as earthquake recording by the same receivers. The traveltime modelling from coincident vertical reflection and refraction observations has been implemented for the two longest regional lines striking EW the Sea of Marmara : one line on the southern rim of the Trough and an other across the succession of basins and highs. The structural constraints for the shallow part is given by the MCS coincident data whereas the basement topography and the structure of the lower crust is sampled and modelled by the OBS and land stations data. This methodology is being extended to the transects that cross these two linesto sense the structure in space and with the help of new structural constraints obtained thanks to Pre-Stack Depth Migration (PSDM). The PSDM has been performed on 3 transects : 2 cross lines in the zone of the Central Basin and an other line in the region connecting the Central Basin to the Cinarcik Basin. The PSDM allowed us to image in details the fine heterogeneity related to the transtensionnal environment. The depth section across the deepest part of the Central Basin gives us information about the geometry and the detailed velocity field for the 5 km thick sedimentary layers when the depth section on the eastern side of this major basin reveals us clearly a new fault, distinct from the one commonly considered. This fault was simply suggested by a conventional seismic processing and which can be interpreted as the south boundary fault which could have caused the rhomboid Central Basin as a pull-apart. The depth section corresponding to the line across the small Kumburgaz Basin and the Central High brings us new constraints on the architecture of the NAF, especially on the northern rim of the Kumburgaz basin. Improving constraints on structure in this latter zone is of critical interest because this is the segment of the NAF which appears silent in current seismicity. This could be either because there is no active fault or because it is aseismic and creeping or in contrary because it is seismogenic and locked. It will be supplemented by detailed earthquake analysis on the OBS data of the survey.
DE: 7230 Seismicity and seismotectonics
DE: 7218 Lithosphere and upper mantle
DE: 3025 Marine seismics (0935)
SC: Seismology [S]
MN: 2004 AGU Fall Meeting