Rayleigh-wave phase velocities in French Polynesia |
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| Authors: | Emile A Okal Jacques Talandier |
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| Institution: | Department of Geology and Geophysics, Box 2161, Yale University, New Haven, Connecticut 06520, USA;Laboratoire de Détection et Géophysique, Commissariat àl'Energie Atomique, Bo te Postale 640, Papeete, Tahiti, French Polynesia |
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| Abstract: | b
Rayleigh-wave phase velocities are investigated in the period range 17–100 s by the two-station method over several paths covering most of French Polynesia. Our results confirm the validity of theoretical models obtained through regionalization of data pertaining to longer paths. They also exhibit a 2–3.5 per cent anisotropy, with the axis of maximum velocity oriented in the direction of spreading of the plate. Part of this anisotropy is, however, due to the presence of the Tuamotu archipelago; when this is removed, the remaining anisotropy (about 1.5 per cent) correlates with the present direction of spreading, indicating that a relaxation of the anisotropy has taken place since the East Pacific ridge jump. Finally, the presence of the Tuamotu Islands explains anomalous waveshapes for surface waves travelling in their vicinity, due to multipathing through their faster structure. |
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