HR: 09:00h
AN: T41A-05    [PDF]
TI: Structure and evolution of a splay fault system in the Tokai segment of Nankai Trough.
AU: * Lallemant, S J
EM: siegfried.lallemant@geol.u-cergy.fr
AF: Departement des Sciences de la Terre, Universite de Cergy-Pontoise, CNRS UMR 7072, 3 avenue du Parc, 8 Le Campus, Bat. I, Cergy-Pontoise, 95031 France
AU: Henry, P
EM: henry@geologie.ens.fr
AF: Laboratoire de Geologie, Ecole Normale Superieure, 24 rue Lhomond, Paris, 75005 France
AU: Martin, V
EM: vmartin@geologie.ens.fr
AF: Laboratoire de Geologie, Ecole Normale Superieure, 24 rue Lhomond, Paris, 75005 France
AU: Martin, V
EM: vmartin@geologie.ens.fr
AF: Centre de Geophysique, Ecole des Mines de Paris, 35 rue St Honore, Fontainebleau cedex, 77305 France
AU: Noble, M
EM: noble@geophy.ensmp.fr
AF: Centre de Geophysique, Ecole des Mines de Paris, 35 rue St Honore, Fontainebleau cedex, 77305 France
AU: Dessa, J
EM: dessa@obs-vlfr.fr
AF: Geosciences Azur, Observatoire Oc‚anographique de Villefranche, La Darse BP 48, Villefranche sur mer, 06235 France
AU: Operto, S
EM: operto@obs-vlfr.fr
AF: Geosciences Azur, Observatoire Oc‚anographique de Villefranche, La Darse BP 48, Villefranche sur mer, 06235 France
AB: The Eastern Nankai Margin was investigated within the framework of the KAIKO-SFJ project by 3D reflection imaging and dense OBS surveying, which yield complementary images of the margin above the seismogenic zone. Prominent features are reflective large scale thrusts observed within the backstop beneath the forearc basin. However, these faults are inactive and distinct from the currently active splay fault system. Subducting basement topography is defined from depth migrated sections. In this area, the volcanoes associated with the Paleo-Zenisu body are not in contact with the wedge backstop and probably lie outside of the seismogenic zone. A deeper body is present but its lateral extension is not known and the uplift and folding of the forearc basin occurred in two phases during the Quaternary and cannot be entirely related to the subduction of the imaged oceanic crust topography. Comparison with the neighbouring Tonankai segment shows the same general structure (suggesting a similar accretion history), but less affected by subducting basement topography. Active splay faults in both segments root at the seaward edge of the backstop, which suggests discontinuities in the accretionary process contribute to define the seismogenic zone. Subducting basement topography is only one factor influencing the splay fault system, which may be better understood combining dynamic branching and shear partitioning processes.
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 8105 Continental margins and sedimentary basins
DE: 9320 Asia
SC: Tectonophysics [T]
MN: 2003 Fall Meeting