HR: 14:25h
AN: S23D-04    [Abstracts]
TI: Structure and Evolution of the Accretionary Margin of Java-Sumatra. Seismic Data and Numerical Modeling Comparisons.
AU: * Kopp, H
EM: hkopp@ifm-geomar.de
AF: IfM-Geomar Abteilung Geodynamik, Wischofstr. 1-3, Kiel, 24148, Germany
AU: Hindle, D
EM: dhindle@ifm-geomar.de
AF: Geologisches Institut Universitaet Freiburg, Albertsrasse 23b, Freiburg, 79104, Germany
AB: We present a numerical model for the evolution of an accretionary prism along a subduction margin. We find the mechanical partitioning of the growing prism into active region, abutting against a deformable backstop, and a relatively undeformed forearc basin is a function of the double tapered basal geometry, where the dip of the detachment is assumed to be opposite above oceanic or continental lithopshere. Varying properties of both materials and detachment can be used to adjust the surface slope and hence geometry of the system, but mechanical partitioning remains essentially the same with the regions becoming broader or narrower. The model appears to closely reproduce the geometry of the Sumatra-Java prism, where a high accretion margin has produced the same distinct mechanical units. Newly prestack depth-migrated marine seismic data reveal the extent and geometry of the active deformation of the deformable backstop, and give indications of some material passing into a subduction channel below the accretionary complex. The deformable backstop appears to be composed of multiple duplex structures, but present day tectonic activity is mostly in the form of transtensive or transpressive deformation, possibly reactivating older dip-slip, accretionary structures. The numerical approach used in the simulation (distinct elements) shows great promise in modelling large deformation in situations such as accretionary prisms, and has also been adapted to incorporate the role of fluid pressure and migration in tandem with large deformation (shortening of the order of 100's of kilometres).
DE: 1031 Subduction zone processes (3060, 3613, 8170, 8413)
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8020 Mechanics, theory, and modeling
DE: 8045 Role of fluids
DE: 8104 Continental margins: convergent
SC: Seismology [S]
MN: 2007 Fall Meeting