HR: 0800h
AN: T41A-0353    [Abstracts]
TI: Deep Structure of the Northeastern Gulf of Aden Margin From Wide-Angle Seismic Network
AU: Watremez, L
EM: watremez@ccr.jussieu.fr
AF: Laboratoire de Tectonique, CNRS-UPMC, 4 place Jussieu, cedex 05, Paris, 75252, France
AU: * Leroy, S
EM: sylvie.leroy@lgs.jussieu.fr
AF: Laboratoire de Tectonique, CNRS-UPMC, 4 place Jussieu, cedex 05, Paris, 75252, France
AU: Rouzo, S
EM: stephane.rouzo@lgs.jussieu.fr
AF: Laboratoire de Tectonique, CNRS-UPMC, 4 place Jussieu, cedex 05, Paris, 75252, France
AU: d'Acremont, E
EM: elia.dacremont@upmc.fr
AF: Laboratoire de Tectonique, CNRS-UPMC, 4 place Jussieu, cedex 05, Paris, 75252, France
AU: Tiberi, C
EM: tiberi@ccr.jussieu.fr
AF: Laboratoire de Tectonique, CNRS-UPMC, 4 place Jussieu, cedex 05, Paris, 75252, France
AU: Burov, E
EM: evgenii.burov@lgs.jussieu.fr
AF: Laboratoire de Tectonique, CNRS-UPMC, 4 place Jussieu, cedex 05, Paris, 75252, France
AU: Al-Lazki, A
EM: lazki@squ.edu.om
AF: University Sultan Qaboos, P.O. Box 50, Al-Khod, Muscat, PC123, Oman
AB: The Gulf of Aden is an oblique rift system with spreading segments connected by several transform faults. Rifting in the gulf began ca. 35 Ma ago when the Afar hotspot activity takes place. Onset of spreading recorded by the first magnetic anomaly (A5d) is dated at least 17.6 Ma. We describe first results from the Encens seismic experiment in the northeastern Gulf of Aden and present crustal-scale images across three second-order segments between Alula-Fartak and Socotra fracture zones. Each of these segments was instrumented with 10-15 km, evenly spaced ocean-bottom seismometers complemented onshore by an array of seismometers. 8000 shots from the 8410 in3 ( ~ 138 l) source on board R/V L"Atalante (Ifremer) have been recorded, providing an extensive dataset, with offsets up to 180 km. Excellent-quality data from this dense source and receiver coverage enable the modeling of the P-waves across and along the strike of the ocean-continent transition (OCT) and continental margin for the different rift segments. Coincident multichannel seismic data is used to better constrain the structure down to the basement, and the crustal structure is eventually validated through the modeling of synthetic gravity anomalies. Our results indicate that a single morphology and geometry of the continental margins does not exist in the eastern Gulf of Aden. Indeed, distinct styles of rifting occur within the first-order segmentation of the gulf, which may be related to pre-rift history and to the syn or post-rift magmatism. The continental crust has a maximum of 35 km thickness in the west and 32 km in the east, with velocities ranging from 6 to 7.3 km/s. The base of the oceanic crust has relatively low P-wave velocities ranging from 6.6 to 7.5 km/s, and a thickness of about 5 km in the west and 7 km in the east. A 130 km long gradual thinning of the crust is observed while the OCT width ranges from 20 to 30 km. The transitional crust is around 8 km thick and the P-wave velocities are upper than 6 km/s. The mantle has P-wave velocities lower than 8 km/s, probably implying serpentinization of the mantle and/or hot mantle. Thermomechanical models contribute to understand the first order parameters that influence passive margins evolution from rifting to present.
DE: 0935 Seismic methods (3025, 7294)
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8109 Continental tectonics: extensional (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting