Geophysical processes and biosphere: article

Аnnotation: In this paper, deep structure of the crust and the upper mantle beneath South-Eastern Asia are studied from surface wave tomography data. For this purpose, a representative dataset of group velocity dispersion curves of Rayleigh (6522 seismic paths) and Love waves (4489 seismic paths) is compiled using a frequency-time analysis technique in the period range 10-250 s. Group velocity distributions at separate periods are calculated using a surface wave tomography method developed for a spherical surface on the basis of the collected data. In total, 18 maps are obtained for each wave type and their horizontal resolution is estimated. To facilitate the interpretation of these maps, local dispersion curves of Rayleigh and Love waves are inverted to SV - and SH -wave velocity sections, respectively, for three different regions: the Tibetan plateau, the Indian plate and the South China sea. Therefore, the obtained distributions of surface wave group velocities allow us to analyze the main large-scale structural features of the crust and the upper mantle beneath south-eastern Asia and connect the revealed velocity heterogeneities with different tectonic units. It is found that at the period of 20 s, minimums of Rayleigh and Love wave group velocities are observed under the regions characterized by large sediment thickness. Minimum and maximum group velocities at the period of 50 s are mainly related to the areas with the thickened and thinned crust, respectively. With increasing the period up to 150 s, the highest group velocity values are attributed to stable tectonic structures (Indian plate, China-Korean and South China platforms, Tarim basin), and their lower values are observed beneath the marginal seas at the east of the study area and the Indochina peninsula. At larger periods, the group velocity variations become smooth, indicating less homogeneous structure of the subasthenospheric layers of the upper mantle, and are not obviously connected with geological structures of the study area.