Depth-variant azimuthal anisotropy in Tibet revealed by surface wave tomography

• Published in: Geophysical research letters Vol. 42; no. 11; pp. 4326 - 4334
• Main Authors: Pandey, Shantanu, Yuan, Xiaohui, Debayle, Eric, Tilmann, Frederik, Priestley, Keith, Li, Xueqing
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 16.06.2015; John Wiley & Sons, Inc; American Geophysical Union
• Series: Depth-variant azimuthal anisotropy in Tibet revealed by surface wave tomography
• Subjects: Alignment; Anisotropy; Asthenosphere; azimuthal anisotropy; Cenozoic; Deformation; Deformation mechanisms; Depth; Direction; Earth Sciences; Lithosphere; Mathematical models; Plate motion; Plates (tectonics); Polarization; Rayleigh wave; Rayleigh waves; Sciences of the Universe; Shear; Shear strain; shear wave splitting; Splitting; Strain; Subduction; Surface water waves; surface wave; Surface waves; Tibet; Tomography; Tibet; China; Myanmar (Burma); Pakistan, Himalayas; China, People's Rep., Xizang; China, People's Rep
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL063921

Azimuthal anisotropy derived from multimode Rayleigh wave tomography in China exhibits depth‐dependent variations in Tibet, which can be explained as induced by the Cenozoic India‐Eurasian collision. In west Tibet, the E‐W fast polarization direction at depths <100 km is consistent with the accumulated shear strain in the Tibetan lithosphere, whereas the N‐S fast direction at greater depths is aligned with Indian Plate motion. In northeast Tibet, depth‐consistent NW‐SE directions imply coupled deformation throughout the whole lithosphere, possibly also involving the underlying asthenosphere. Significant anisotropy at depths of 225 km in southeast Tibet reflects sublithospheric deformation induced by northward and eastward lithospheric subduction beneath the Himalaya and Burma, respectively. The multilayer anisotropic surface wave model can explain some features of SKS splitting measurements in Tibet, with differences probably attributable to the limited back azimuthal coverage of most SKS studies in Tibet and the limited horizontal resolution of the surface wave results. Key Points Surface wave tomography revealed depth‐dependent azimuthal anisotropy in Tibet The dominant fast direction is EW at shallower depths and NS at greater depths The surface wave model can predict some features of SKS splitting measurements