Shear wave anisotropy beneath the Tibetan Plateau
作者： Daniel E. McNamara , Thomas J. Owens , Paul G. Silver , Frances T. Wu
DOI: 10.1029/93JB03406
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摘要: Eleven broadband digital seismic stations were deployed across the central Tibetan Plateau in first extensive passive-source experiment attempted within Plateau. One year of recording resulted 186 event-station pairs which we analyze to determine characteristics shear wave splitting upper mantle beneath array. Measurements fast polarization direction (ϕ) and delay time (δt) for SKS direct S arrivals reveal systematic variations along north-south oriented In north region plateau, very large times are observed at three stations, largest is BUDO with δt=2.4 s. However, TUNL, off northern edge plateau 110 km from BUDO, sites south δt decreases by nearly a factor 3. We also observe rotation ϕ about 45° (NE) 90° (E-W) A previously identified zone inefficient Sn propagation correlates well our observations. The suggest that relateively high number anisotropic crystals preferentially alligned mantle-lid, portion most cases, directions appear be parallel surface geologic features suggesting as much 200 has been involved collisional deformation produced
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