HR: 0800h
AN: T31C-0595    [Abstracts]
TI: Structural Insight of the Eastern Marmara Sea by Combined Multichannel Seismics and Refraction Tomography
AU: DESSA, J
EM: dessa@geoazur.obs-vlfr.fr
AF: UPMC/UMR Géosciences Azur, 2 quai de la Darse, BP 48, Villefranche-sur-Mer, 06235, France
AU: CARTON, H
EM: carton@ipgp.jussieu.fr
AF: IPGP/Équipe de Géosciences Marines, 4 place Jussieu, Paris, 75252, France
AU: * SINGH, S C
EM: singh@ipgp.jussieu.fr
AF: IPGP/Équipe de Géosciences Marines, 4 place Jussieu, Paris, 75252, France
AB: At least the eastern 2/3 of the Marmara Sea constitute a well-documented seismic gap since they are the only part of the North Anatolian strike slip system that was not ruptured during the 20th century. The 60 km-long Cinarcik Basin is the easternmost basin of the Marmara Sea, immediately east of which the rupture of the destructive 1999 Izmit earthquake has stopped. The seismotectonic regime within the Marmara Sea has been subject to debates, that have for a large part concerned the Cinarcik basin, and whose implications are important in terms of seismic hazard in the densely populated area of Istanbul. Different hypotheses have been proposed, essentially based on shallow geophysical studies. Deep investigations are a necessary complement to gain a better insight of the structures and their evolution. We present here the results obtained from data collected during the SEISMARMARA cruise in 2001. A dense set of 81 multichannel seismic lines has been acquired whose shots were also recorded by an array of 13 ocean bottom seismometers deployed throughout the basin. Wide-angle data were processed by refraction tomography that provided a 3D model of P-wave velocities spanning over 66x36 km. The MCS data were classically processed through a stacking and migration procedure, and eventually depth-converted using the velocity model. This provides us with both a quantitative assessment of the broad structures and a geometrically accurate image of the fine structural setting down to ~ 8 km depth. The interpretation of these data brings an insight of the crustal processes responsible for the formation of the basin and its subsequent evolution, recorded by the sedimentary in-fill. This analysis reveals high velocities within the basement underlying the basin, possibly implying a thinning of the lithosphere by removal of the upper crust. Within the sedimentary basin, a strong spatial variability and a significant tectonic complexity is observed; this is directly related to the dominant strike slip motion of the North Anatolian system and to the geometric complexity of structures with respect to this general kinematics.
DE: 3025 Marine seismics (0935, 7294)
DE: 3075 Submarine tectonics and volcanism
DE: 7270 Tomography (6982, 8180)
DE: 8012 High strain deformation zones
DE: 8111 Continental tectonics: strike-slip and transform
SC: Tectonophysics [T]
MN: 2007 Fall Meeting