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We apply seismic tomography to 590,213 P‐wave arrival‐time data of 23,486 local earthquakes and 300,051 relative travel‐time residuals of 27,492 teleseismic events to study the 3‐D velocity structure of the crust and upper mantle beneath the entire Philippine Sea Plate (PSP) and its adjacent areas. Our results reveal significant high‐velocity anomalies beneath the Philippine Trench, the Japan‐Izu‐Bonin‐Mariana Trench, and the Nankai Trough, which reflect the subducted Philippine Sea slab, the Pacific slab, and the Shikoku Basin, respectively. On the basis of the tomographic images, we construct morphological models of these slabs. The slab morphologies become complex from the east to west. Taking into account previous results of geochemistry, paleomagnetism and numerical simulations, we deem that the complicated morphologies of the subducted slabs are related to the slab age, subduction rate, collision between different plates, clockwise rotation of the PSP, and retreat rate of trenches. Plain Language Summary: The Philippine Sea Plate (PSP) is almost entirely surrounded by subduction zones. We use P‐wave tomography to study the 3‐D velocity structure of the crust and upper mantle beneath the entire PSP for a better understanding of the slab geometry and subduction dynamics. Our tomographic results reveal obvious high‐velocity (high‐V) anomalies beneath the trenches around the PSP, which reflect the subducting Philippine Sea slab, the Pacific slab, and the Shikoku Basin. We construct morphological models of these slabs according to their high‐V anomalies. These slab exhibit quite different morphologies. Taking into account previous geochemical, paleomagnetic and numerical simulation results, we think that the complex slab morphologies are related to the slab age, subduction rate, collision between different plates, clockwise rotation of the PSP, and retreat rate of oceanic trenches. Key Points: P‐wave tomography is applied to investigate 3‐D velocity structure down to 800 km depth beneath the entire Philippine Sea PlateThe subducting Pacific and Philippine Sea slabs exhibit quite different morphologiesThe morphological differences are caused by the slab age, subduction history and interactions between slab and surrounding mantle [ABSTRACT FROM AUTHOR]

Massive lithospheric thinning occurred in eastern China and large‐scale magmatism in South China occurred in the Mesozoic. Some geodynamic models have been proposed to explain their mechanisms, but are not consistent with each other. We apply anisotropic tomography to 32,728 P‐wave travel time data of 479 teleseismic events recorded at 225 stations to study the 3‐D anisotropic Vp structure of the upper mantle beneath central‐east China. P‐wave radial anisotropy is investigated for the first time in the study region. Our results show that an obvious low‐velocity zone exists in the asthenosphere under the eastern part of our study region, which represents upwelling thermal flow from the Cathaysia block to the North China block (NCB) according to the results of azimuthal and radial anisotropies. A distinct high‐velocity zone with weak radial anisotropy exists under the middle Yangtze block, which is explained as the stable cratonic root. Two other weak high‐velocity zones appear near or within the mantle transition zone under the middle‐lower Yangtze River and the eastern NCB, which might be detached lithosphere or the stagnant Pacific slab. Combining with previous geological and geochemical results, we consider that both the NCB and the South China block have undergone a common geodynamic process in the Mesozoic due to their similar age trending of igneous rocks, which could be explained by a flat‐slab subduction model and a ridge subduction model. These two models are associated with the paleo‐Pacific plate subduction that might have played a key role in the evolution of eastern China. Key Points: Anisotropic tomography is applied to study the 3D anisotropic velocity structure under central‐east ChinaMantle flow with low P‐wave velocity upwells and moves from the Cathaysia block to the North China blockThe paleo‐Pacific plate subduction might have prompted the thermal material migration [ABSTRACT FROM AUTHOR]

Abstract: During 2006 to 2007, a small array of broadband seismic stations was deployed across the eastern Qaidam–Kunlun border. Receiver functions derived from this data set show a coherent P-to-S converted phase from the Moho at ~65km to ~58km below sea level (b.s.l.) from south to north beneath the Kunlun mountains. The Moho is observed at ~45km b.s.l. beneath the Qaidam basin. A sharp offset of ~15km in the Moho depth is observed just beneath the Qaidam–Kunlun border. The close correlation between the surface topography and the sharp Moho offset substantiates the view that the Kunlun crust is weaker than that of the Qaidam basin and thickens vertically in response to compression between India (through the Tibetan plateau) and the Qaidam basin. Furthermore, a strong steeply north-dipping converted phase can be seen from ~5 to 15km b.s.l. north of the North Kunlun Fault, which is likely a major south-directed thrust fault partially responsible for the thickening of the Kunlun crust. [Copyright &y& Elsevier]

• Tomography with a dense seismic array reveals the upper-mantle structure in SE China. • A low-velocity zone with high Poisson's ratio exists under the western Cathaysia block. • The low-velocity zone reflects thermal flow causing the late Mesozoic mineralization. Our study region is located in the Cathaysia block (CB), Southeast China. The most significant feature of the CB is the widespread Mesozoic magmatism and poly-metallic mineralization. However, there is still no consensus on their genesis and related tectonic processes. In this study, we determine high-resolution (0.3° in the horizontal direction) tomographic images of Vp and Vs and Vp/Vs ratio in the crust and upper mantle using 6773 P-wave and 4526 S-wave travel-time data of teleseismic events recorded by a broadband linear seismic array. The array was deployed by our team in the middle part of the CB, consisting of 81 portable stations with an interval of 5–8 km. Our tomographic results reveal two obvious low-velocity (low-V) zones with high Vp/Vs ratio (high-σ) beneath the Nanling ore belt and the Wuyishan terrane, which may reflect magmatic channels formed by partial melting that may provide heat for metal mineralization. Two high-V anomalies with low-σ are located beneath the western Wuyishan terrane and the eastern CB, which may represent refractory lithosphere or remnants of delaminated lithospheric material caused by underplating of the magma due to the subduction of the paleo-Pacific plate and its following rollback. There exists an anomaly with low-Vp, high-Vs and low-σ at depths of 150–300 km beneath the western Wuyishan terrane, which may be related to the reserved trace of magmatic conduits. On the basis of the tomographic results, we propose a geodynamic model to explain the deep mechanism of mineralization beneath the CB. [ABSTRACT FROM AUTHOR]

A mineralization zone exists in the Middle and Lower Yangtze River (MLYR) region. Previous studies have shown that this zone might be caused by the rich ejection of magma in the Mesozoic. We have applied the teleseismic tomography method to determine a 3-D P-wave velocity structure of the mantle down to 500km depth beneath this region by using 14,740 P-wave arrival times collected from 519 teleseismic events recorded by 46 portable and 47 static seismic stations located in this region. The relative residual times used for the tomography are calculated by the modified multi-channel cross-correlation method which increases not only the efficiency but also the data precisions up to 0.01s. The grid space is set as 1°×1° horizontally and 50–100km vertically. Our tomographic results show that the lithosphere with high velocity anomalies is separated into two parts: one locates above the depth of 100km and the other at the depths between 250km and 400km, and the asthenosphere with low velocity anomalies locates between these two parts of lithosphere, which indicates that the lithosphere delaminated together with the asthenosphere upwelling. The detachment of lithosphere might relate to the subduction of the western Pacific slab. Therefore, our study provides clear evidence to geoscientists for understanding the deep dynamic process beneath this region and a three-stage geodynamic process is developed based on the new evidence. [ABSTRACT FROM AUTHOR]

[Display omitted] • A teleseismic full waveform inversion method is used to study the crustal velocity. • A low velocity zone corresponds to the faulting, seismic zone, and ore deposits very well. • The seismic pumping might cause the upwelling of thermal flow. It is crucial to image the crustal velocity structure with higher resolution to understand the relationship between crustal seismicity and metallogenic mechanisms, which remain challenging targets for conventional seismic tomography. Teleseismic tomography via body-waves can image velocity well in the upper mantle, but poorly in the crust. In this study, we have developed a teleseismic full waveform inversion (TFWI) method based on the frequency-wavenumber spectral element method (FK-SEM) hybrid to improve the resolution of teleseismic P-waves in the crust. We used the TFWI method to study the crustal velocity by using two large teleseismic events recorded by 29 portable stations with ~5 km intervals across the Zhenghe-Dapu Fault (ZDF) in the Cathaysia Block. This is the first attempt using the FK-SEM hybrid on real data. As expected, we obtained a 2D velocity model in the crust that had high lateral resolution. There is an obvious low velocity zone (LVZ) in the crust below east side of the ZDF, while a relatively high velocity anomaly exits within its west side. Combined with previous geochemical and geological results, this LVZ is explained as remnant magma due to the large-scale magmatism in the Late Jurassic and Early Cretaceous. According to the spatial correlation among the LVZ, local earthquakes, faulting, and major ore deposits, we consider that seismic pumping might be a mechanism of thermal fluid transport for the mineralization. [ABSTRACT FROM AUTHOR]