Thursday, 30 August 2007 - 4:20 PM
4.P2.C-3

Upper mantle anisotropy from teleseismic SKS splitting beneath Lützow-Holm Bay region, East Antarctica

Yusuke Usui, Transdisciplinary Research Integration Center, Research Organization of Information and Systems, 1-9-10 Kaga, Itabashi-ku, Tokyo, 173-8515, Japan, Masaki Kanao, Polar Data Center, National Institute of Polar Research, 1-9-10 Kaga, Itabashi-ku, Tokyo, Japan, Atsuki Kubo, Kochi Earthquake Observatory, Faculty of Science, Kochi University, 2-17-47, Asakura Honmachi, Kochi, 780-8073, Japan, Yoshihiro Hiramatsu, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan, and Hiroaki Negishi, Earthquake Disaster Mitigation Research Center, National Research Institute for Earth Science and Disaster Prevention, 1-5-2, Wakinohama-Kaigandori, Chuo, Kobe, 651-0073, Japan.

Investigations of digital seismograph records from eight stations around the Lützow-Holm Bay region have improved our understanding of the evolution of the Antarctic plate through the analysis of SKS wave splitting from teleseismic events. The observed delay times are around 1.2 s and are equal to the global average of SKS splitting. The observed fast polarization directions are mainly oriented NE–SW in the region. This direction is consistent with the paleo-compressional stress during the Pan-African age (~500 Ma). We consider that the origin of mantle anisotropy is the lattice-preferred orientation which was caused by Gondwana assembly, rather than the present asthenospheric flow that is parallel to the absolute plate motion. The anisotropy is assumed to have been produced during the Pan-African orogeny and the pre-existing structure may also influence the formation of the anisotropy during Gondwana break-up.

[Manuscript]

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