[1] This paper presents a tomographic study on the S wave velocity structure of China and adjacent regions. Group velocity dispersions of fundamental Rayleigh waves along more than 4000 paths were determined with frequency-time analysis. The study region was divided into a 1°Â 1°grid, and velocities in between grid nodes were calculated by bilinear interpolation. The Occam's inversion scheme was adopted to invert for group velocity distributions. This method is robust and allows us to use a fine grid in model parameterization and thus helps to restore a more realistic velocity pattern. Checkerboard tests were carried out, and the lateral resolution was estimated to be 4°-6°in China and its eastern continental shelves. The resulting group velocity maps from 10 to 184 s showed good correlation with known geological and tectonic features. The pure path dispersion curves at each node were inverted for shear wave velocity structures. The threedimensional velocity model indicates thick lithospheres in the Yangtze and Tarim platforms and hot upper mantles in Baikal and western Mongolia, coastal area and continental shelves of eastern China, and Indochina and South China Sea regions. The Tibetan Plateau has a very thick crust with a low-velocity zone in its middle. Beneath the crust a north dipping high-velocity zone, mimicking a subducting plate, reaches to 200 km in depth and reaches to the Kunlun Mountains northward. In northern Tibet a low-velocity zone immediately below the Moho extends eastward then turns southward along the eastern edge of the plateau until it connects to the vast low-velocity area in Indochina and the South China Sea.INDEX TERMS: 7218 Seismology: Lithosphere and upper mantle; 7255 Seismology: Surface waves and free oscillations; 9320 Information Related to Geographic Region: Asia;

No abstract

No abstract

No abstract

SKS wave splitting measurement is a powerful tool to characterize mantle deformation and study the dynamics and evolution of continents. We have made measurements of SKS wave splitting beneath the China mainland and adjacent regions. Our goal is to obtain the magnitude and orientation of upper mantle anisotropy and provide constraints for the evolution model of the crust and mantle. We use the technique of Silver and Chan to determine SKS wave splitting parameters at more than 80 three‐component broadband stations in China and neighboring regions, including the azimuths of fast polarization direction (ϕ) and delay times of split shear wave (δt). The fast wave polarization directions at most stations share a common preferred orientation in a same tectonic block. The fast axes show good correlation with the past and present‐day tectonic movement. Delay times range from 0.4s to 2.4s with an average about 1.2s. According to the splitting parameters of SKS wave, anisotropic characteristics in the study region are analyzed to investigate the dynamic process in the Earth.

[1] We present a surface wave study aimed to resolve the azimuth-dependent propagation velocities of Rayleigh waves (10 -184s) in East Asia. The resultant anisotropy patterns demonstrate that East Asia consists of a number of tectonic domains, each displays a characteristic and selfconsistent deformation mode. The depth variation of the anisotropy pattern in each domain helps to understand the boundary actions on the lithosphere and the depth-varying deformation styles owing to rheology change.

This paper presents the result of a surface wave study on azimuthal anisotropy in the crust and upper mantle of North China, and makes a preliminary comparison with the result of S‐wave splitting in the region. The anisotropy pattern of Rayleigh waves of different periods exhibits obvious lateral variation, which is closely related with the tectonic divisions and vertical layering of the crust and upper mantle of North China. In the stable blocks of Ordos and Alxa significant anisotropy is rather uniform in the lithospheric mantle down to 160 km; while in the eastern part of the North China Craton, where lithosphere thinning occurred in Meso‐Cenozoic time, no azimuthal anisotropy is detected in the depth range of 80~150 km, which may indicate that no significant horizontal tectonic movement occurred during the process of lithospheric thinning. The anisotropy in the study region is characterized by obvious layering, as evidenced by the inversion result from surface waves. On the other hand the remarkable scatter of apparent splitting parameters may also be attributed to multi‐layering and/or slanting symmetry axis of the anisotropy. Assuming a multi‐layer anisotropy model, the differences between surface wave and S‐wave splitting in most cases can be qualitatively explained. In the future study the detecting depth and resolving power of surface wave should be increased and more splitting measurements are needed in order to establish a quantitative or semi‐quantitative 3D anisotropy model.

We advance evidence for the existence of seismic anisotropy in the upper mantle beneath Southern Germany from the dispersion of Love and Rayleigh waves. The evidence is based upon a substantial Love‐Rayleigh discrepancy observed between periods of 40 s and 120 s. An isotropic mantle model clearly fails to explain the observed dispersion curves. Systematic inversion experiments with transversely isotropic models show that anisotropy at depths between 70 km and 200 km is sufficient to explain the observed dispersion curves. Our data require neither anisotropy at greater depths nor anisotropy in the crust though we cannot exclude its presence there. A search for azimuthal anisotropy of Rayleigh wave propagation indicates a weak, but possibly insignifant azimuthal anisotropy of about 1% for periods less than 40 s with fast directions between 20 and 50 degrees east of north. At larger periods azimuthal anisotropy is less than 1% and the fast directions scatter considerably as period varies.