HR: 1340h
AN: T53A-1112    [Abstracts]
TI: Imaging Deep Structure of Sumatra Megaquake Fault Plane Using Long Offset Marine Seismic Reflection Data
AU: * Hananto, N
EM: hananto@ipgp.jussieu.fr
AF: Laboratoire de Geosciences Marines, Institut de Physique du Globe de Paris, 4 Place Jussieu, Tour 14, 5eme etage, Paris, 75252,
AU: Singh, S
EM: singh@ipgp.jussieu.fr
AF: Laboratoire de Geosciences Marines, Institut de Physique du Globe de Paris, 4 Place Jussieu, Tour 14, 5eme etage, Paris, 75252,
AU: Carton, H
EM: carton@ipgp.jussieu.fr
AF: Laboratoire de Geosciences Marines, Institut de Physique du Globe de Paris, 4 Place Jussieu, Tour 14, 5eme etage, Paris, 75252,
AB: Seismic reflection imaging in subduction zone environment is hampered by poor penetration of seismic energy in deformed sediments, seafloor scattering and severe water bottom multiples. To image deep structure, we require a very large source rich low frequencies and a very long streamer. We use the data acquired by WesternGeco marine vessel Geco Searcher in July 2006 towing two long streamers (5.5 and 12.5 km) and 10170 cubic inch airgun array source. Different offset data contain information on different structures. Therefore, instead of using conventional stacking procedure, we have developed offset optimisation and horizon consistent velocity analysis techniques where data from different offsets are stacked for different horizons, which provide a higher quality image, particularly of deep structures that are generally hindered by noise. Since deep reflectors are generally broken up due scattering noise from near surface structures and do not have diffraction tails, conventional post-stack migration of data leads to severe smiles at the extremities of deep reflections and scattered noise. We iteratively build a migration velocity based on constant velocity migration that provide the best migrated image of deep structure and then performed a 2D Kirchhoff migration technique leading to a better quality image. Our re-processed image clearly shows the top and bottom of the down going oceanic plate and deep penetrating faults that seem to cut through the oceanic crust and go down in the mantle.
DE: 3025 Marine seismics (0935, 7294)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting