HR: 1340h
AN: T23A-1198    [Abstracts]
TI: Lithospheric and Upper-Mantle Structure of the Red Sea and Arabian Peninsula
AU: * Hansen, S E
EM: shansen@es.ucsc.edu
AF: University of California, Santa Cruz, 1156 High St., Santa Cruz, CA 95064, United States
AU: * Hansen, S E
EM: shansen@es.ucsc.edu
AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94551, United States
AU: Schwartz, S Y
EM: susan@es.ucsc.edu
AF: University of California, Santa Cruz, 1156 High St., Santa Cruz, CA 95064, United States
AU: Rodgers, A J
EM: rodgers7@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94551, United States
AU: Gaherty, J B
EM: gaherty@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, P.O. Box 1000 61 Route 9W, Palisades, NY 10964, United States
AU: Al-Amri, A M
EM: amsamri@ksu.edu.sa
AF: King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia
AB: Using broadband seismic data recorded by various networks, a variety of techniques have been employed to investigate the lithospheric and upper-mantle structure of the Red Sea and Arabian Peninsula. This presentation will summarize our findings and conclusions about the tectonic evolution and current state of the Arabian Plate. S-wave receiver functions provide constraints on the lithospheric thickness and reveal very thin lithosphere (40-80 km) along the Red Sea coast, which thickens rapidly toward the interior of the Arabian Shield (100-120 km). A step of 20-40 km in lithospheric thickness is also observed at the Shield-Platform boundary. Mantle anisotropy has been analyzed using shear-wave splitting of teleseismic SKS waveforms. The consistent north-south oriented fast directions are not adequately explained by end-member models of fossilized anisotropy and present-day plate motion and have instead been explained by a combination of plate- and density-driven flow in the asthenosphere. Further constraints on the upper mantle velocity and anisotropy have been obtained by jointly inverting the receiver function constraints with frequency dependent surface wave phase delays. The results demonstrate that the thin lithospheric lid is underlain by a pronounced low-velocity zone and that anisotropy is required in both the lithosphere and asthenosphere. Attenuation and thermal estimates are also being explored and preliminary results will be presented. The combined results of these studies support a two-stage rifting history for the Red Sea, where extension and erosion by asthenospheric flow are responsible for variations in the lithospheric thickness. These lithospheric variations guide asthenospheric flow beneath western Arabia and the Red Sea, leading to a large-scale thermal anomaly that is associated with Cenozoic uplift and volcanism. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under contract W-7405-Eng-48. UCRL-ABS-234290.
DE: 7218 Lithosphere (1236)
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8109 Continental tectonics: extensional (0905)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting