Al-Amri, A.

Hansen, S.

Nyblade, A.

Park, Y.

Rodgers, A.

Tkalcic, H.

UNT Digital Library

LLNL-PROC-406567Structure of the Lithosphere andUpper Mantle Across the ArabianPeninsulaA. Al-Amri, A. Rodgers, S. Hansen, A. Nyblade, Y.Park, H. TkalcicAugust 26, 2008American Geophysical UnionSan Francisco, CA, United StatesDecember 15, 2008 through December 19, 2008Disclaimer  This document was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor Lawrence Livermore National Security, LLC, nor any of their employees makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or Lawrence Livermore National Security, LLC. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or Lawrence Livermore National Security, LLC, and shall not be used for advertising or product endorsement purposes.  Structure of the Lithosphere and Upper Mantle Across the Arabian PeninsulaAbdullah Al-AmriGeology and Geophysics Department, King Saud University, Riyadh, Saudi ArabiaArthur RodgersAtmospheric, Earth and Energy Division, Lawrence Livermore National Laboratory, Livermore CA USASamantha Hansen, Andrew NybladeDepartment of Geosciences, Pennsylvania State University, State College, PA USAYongcheol ParkNational Institute of Meteorological Research, Seoul, South KoreaHrvoje TkalcicResearch School of Earth Sciences, The Australian National University, Canberra ACT, AustraliaTectonic structure of the Arabian Peninsula is revealed by analysis of modern broadband (BB) waveform data from the region.  This presentation will report inferences of seismic structure of the Arabian Peninsula using various techniques and interpretations of its tectonic significance.  Several studies have been undertaken using data from the Saudi Arabian National Digital Seismic Network (SANDSN) which consists of 38 (26 BB, 11 SP) stations, mostly located on the Arabian Shield.  Additional data were taken from the 1995-7 Saudi Arabian IRIS-PASSCAL Deployment (9 BB stations) and other stations across the Peninsula.  Crustal structure, inferred from teleseismic P-wave receiver functions, reveals thicker crust in the Arabian Platform (40-45 km) and the interior of the Arabian Shield (35-40 km) and thinner crust along the Red Sea coast.  Lithospheric thickness inferred from teleseismic S-wave receiver functions reveals very thin lithosphere (40-80 km) along the Red Sea coast which thickens rapidly toward the interior of the Arabian Shield (100-120 km).  We also observe a step of 20-40 km in lithospheric thickness across the Shield-Platform boundary.  Seismic velocity structure of the deep upper mantle inferred from teleseismic P- and S-wave travel time tomography reveals large differences between the Shield and Platform, with the Shield being underlain by slower velocities, ±3% for P-waves and ±6% for S-waves.  Shallower upper mantle structure inferred from Rayleigh wave phase velocities and indicates that low-velocity material is channeled beneath the Red Sea below 150 km and pools beneath the Arabian Shield above this depth.  Seismic anisotropy inferred from shear-wave splitting, reveals a splitting time of approximately 1.4 seconds, with the fast axis slightly east of north.  The shear-wave splitting results are surprisingly consistent across the Peninsula, with a slight clockwise rotation parallel for stations near the Gulf of Aqaba.  In summary, these results allow us to make several conclusions about the tectonic evolution and current state of the Arabian Plate.  Lithospheric thickness implies that thinning near the Red Sea has accompanied the rupturing of the Arabian-Nubian continental lithosphere.  The step in the lithospheric thickness across the Shield-Platform boundary likely reveals a pre-existing difference in the lithospheric structure prior to accretion of the terranes composing the eastern Arabian Shield.  Tomographic imaging of upper mantle velocities implies a single large-scale thermal anomaly underlies the Arabian Shield and is associated with Cenozoic uplift and volcanism.  Hot material from the Afar Hot Spot is channeled along the Red Sea by lithospheric topography.This abstract is prepared for the 2008 American Geophysical Union Meeting, December 15-19 2008 and will be submitted to Special Session T19: Tectonic Structure of the Middle East    This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Structure of the Lithosphere and Upper Mantle Across the Arabian Peninsula

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