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This paper aims to improve the robustness of interpretation in the S receiver function (SRF), a technique commonly used to retrieve forward scattering of S -to- P converted waves (Sdp) originated from the lithosphere–asthenosphere system (LAS) beneath the stations. Although the SRF does not suffer interferences from backward scattering waves such as the first multiples from the Moho, one major drawback in the method is that Sdp phases can interfere with P coda waves and it is conceivable that these signal-generated noise may be misinterpreted as Sdp phase from the LAS beneath seismic stations. Through systematic analysis of full-waveform synthetics and SRFs from catalogued source parameters, we find that the strong P coda waves before the S wave in the longitudinal-component waveforms result in unwanted signal-generated noise before the S wave in the synthetic SRFs. If the mean amplitude of SRFs after the S wave is large, dubious signal-generated noise before the S arrival are strong as well. In this study, we honor the level of these unwanted signal-generated noise and devise data-oriented screening criteria to minimize the interference between P coda waves and genuine S -to- P converted waves. The first criterion is LQR, a direct measure of the amplitude ratio between longitudinal P coda waves and radial S wave in the waveform data. The second criterion is AMP, the amplitude of SRFs after the S arrival. We illustrate that these criteria effectively measure the energy level of mantle waves such as the SP wave. With synthetics and real data, we demonstrate the effectiveness of LQR and AMP criteria in minimizing these unwanted signal-generated noise in the stacked SRFs down to 1–2 per cent, improving detection threshold and interpretation of Sdp phases from seismic discontinuities in the LAS. [ABSTRACT FROM AUTHOR]

Abstract: Using the teleseismic P- and S-wave receiver functions of the dense linear temporary seismic array, the crust and uppermost mantle structures beneath the deep large faults in the northeastern margin of the Tibetan Plateau were imaged. The images of the first converted wave and the multiples indicated that the North Fault Zone of West Qinling (NWQ) Mountain and Diebu–Lueyang (DBL) faults cut the Mohorovicic (Moho) Discontinuity and cause an obvious difference feature for the Moho in the two sides of the faults. The higher Vp/Vs ratio and lower velocity layer is found beneath the west portion of the array near the Tibetan Plateau, which implies a lower crust channel flow coming from the Tibetan Plateau. The weak Moho and higher Vp/Vs ratio beneath the eastern portion of the array near the Ordos suggest the upwelling of the hot mantle material. The results also indicate an obvious deformation in the upper crust with the lower Vp/Vs ratio beneath the middle of the array. Such upper crust deformation is closely related to the topography of the surface; therefore, we deduce that the deformation of the brittle upper crust is accompanied by the formation of the local topography during the uplift of the Tibetan Plateau, which is also the primary reason for the active seismicity in the study region. The deformation of the lithosphere–asthenosphere boundary (LAB) can also be associated with the formation of the diapir caused by the upwelling hot materials in the upper mantle due to the uprising of the thrusting plate caused by the subduction of the India Plate. The existence of the lower crust channel flow, the crust shortening, and the mantle diapir in the local region simultaneously implies that the elevation and formation of the Tibetan Plateau cannot be explained with a single model. The higher resolution results for the crust and the mantle, especially beneath the block boundary region, are necessary to construct the completed geodynamic model to understand the formation of the Tibetan Plateau. [Copyright &y& Elsevier]

As a traditional method, passive seismic exploration is used to construct the body-wave velocity structure of the upper crust, but it is cost-ineffective and depth-limited when applied to large areas. In this study, we use another more economical method to determine the S-wave velocity (SWV) of the upper crust based on the principle that the amplitude of the direct P-wave on the teleseismic receiver function is sensitive to the upper crust. Using the amplitudes of the massive receiver functions from permanent broadband seismic stations, the SWV structure of the upper crust is obtained in the coastal area of South China (CASC). A pattern of high to low SWVs is exhibited across the study area, with SWVs varying about 2.5–3.7 km/s from west to east. In the profile parallel to the coastline, lateral variations in the SWV correspond to the fault zone, indicating that the cutting depth of most coastal faults is approximately 10 km. Referring to previous studies, we deduce that the low SWV in most sub-areas can be interpreted as the joint effect of the sedimentary layer of the alluvial plain and the accumulation of underground heat flows, in addition to multistage fracturing tectonism. Moreover, the gradual change in the SWV in each profile from the surface to approximately 10 km is correlated with multiple invasions and the coverage of volcanic rocks, to a certain extent. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crustal anisotropy is mainly distributed in the middle-lower crust of the South China block. • The dominant fast direction is generally near NW–SE with average delay time ∼ 0.33 s. • The crust-mantle may be coupled deformation. • A few NE–SW directions of anisotropy may be the "fossil" deformation during the Paleozoic. Exploiting the teleseismic waveform data from permanent seismic stations distributed in the South China block, we obtained the crustal anisotropy parameters at 51 stations by fitting the azimuthal variations of arrival times of the P M s converted wave of radial receiver functions. The results show the dominant direction of fast wave polarity in the South China block is NW–SE, which is basically consistent with the absolute plate motion direction. Combining the shear wave splitting and GPS results, we speculated that the tectonic extension of the Paleo-Pacific plate subduction dominates the crust–mantle anisotropy, which reflects the large-scale tectonic stress setting of the South China block. The fast wave directions of NE–SW and E–W calculated by a few stations might represent a local complex tectonic environment, and the crustal anisotropy of NE–SW is well related to the tectonic deformation in Paleozoic. The delay time of slow waves caused by crustal anisotropy ranges from 0.14 s to 0.71 s, with an average of 0.33 s. The delay time of Jiangnan orogenic belt, which located in the southeast of Yangtze block, is particularly large, which reflects the complex and intense intra-continental tectonic movements since Neoproterozoic. The crustal anisotropy along the southeast coast can be contributed to the local lithosphere underplating caused by the upwelling of asthenosphere in Cretaceous. [ABSTRACT FROM AUTHOR]