HR: 1340h
AN: T33B-0547    [Abstracts]
TI: Advanced Seismic Imaging of Subduction Related Structures at the North Chile Convergent Margin
AU: * Sick, C
EM: sicky@geophysik.fu-berlin.de
AF: Freie Universität Berlin, Fachrichtung Geophysik Malteserstr. 74-100, Berlin, D-12249 Germany
AU: Buske, S
EM: buske@geophysik.fu-berlin.de
AF: Freie Universität Berlin, Fachrichtung Geophysik Malteserstr. 74-100, Berlin, D-12249 Germany
AU: Shapiro, S
EM: shapiro@geophysik.fu-berlin.de
AF: Freie Universität Berlin, Fachrichtung Geophysik Malteserstr. 74-100, Berlin, D-12249 Germany
AB: Within the framework of the CINCA project in 1995, the subducting Nazca plate offshore Chile between approximately 19°S and 26°S has been investigated. The aim of this study was to deliver improved images of the structures of the oceanic crust as well as of the subducting plate and the oceanic Moho. We processed two marine profiles crossing the trench using different imaging techniques. First, we applied prestack Kirchhoff depth migration to the data to get an impression of the main structures within the crust. In some depth regions along the profiles, the resulting images are dominated by strong migration smiles. To avoid these artifacts and to improve the seismic images, we applied Fresnel migration to the data sets. As an extension of Kirchhoff depth migration the Fresnel migration restricts the migration operator to the area in the subsurface that physically contributes to the recorded signal. The resulting sections from both processing techniques give detailed insights into the subsurface structures and especially of the subducting Nazca plate near the trench region. While the Kirchhoff results show the typical horst-and-graben structures of the ocean bottom in the bending zone of the subducting plate seaward of the trench, the Fresnel images additionally exhibit structures indicating that also thrust faulting might be present. East of the trench, subducted horst-and-graben structures in the subsurface can be observed as well as fault systems at the continental slope parallel to the subducting plate. Several features can be seen in both sections but the Fresnel migration leads to more continuous images of the subsurface structures as for example of the normal fault system below the continental slope.
DE: 7200 SEISMOLOGY
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8104 Continental margins: convergent
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: Fall Meeting 2005