The fate of the colliding Indian and Asian tectonic plates below the Tibetan high plateau may be visualized by, in addition to seismic tomography, mapping the deep seismic discontinuities, like the crust-mantle boundary (Moho), the lithosphere-asthenosphere boundary (LAB), or the discontinuities at 410 and 660 km depth. We herein present observations of seismic discontinuities with the P and S receiver function techniques beneath central and western Tibet along two new profiles and discuss the results in connection with results from earlier profiles, which did observe the LAB. The LAB of the Indian and Asian plates is well-imaged by several profiles and suggests a changing mode of India-Asia collision in the east-west direction. From eastern Himalayan syntaxis to the western edge of the Tarim Basin, the Indian lithosphere is underthrusting Tibet at an increasingly shallower angle and reaching progressively further to the north. A particular lithospheric region was formed in northern and eastern Tibet as a crush zone between the two colliding plates, the existence of which is marked by high temperature, low mantle seismic wavespeed (correlating with late arriving signals from the 410 discontinuity), poor Sn propagation, east and southeast oriented global positioning system displacements, and strikingly larger seismic (SKS) anisotropy.Tibetan lithosphere | receiver functions | anisotropy I t has long been recognised that the Tibetan plateau was created by the collision of the northward moving Indian plate and the relatively stationary Asian plate, which began about 50 million yr ago (1). However, the mode of deformation of the mantle lithospheres (2) remained largely unknown. A fundamental question is whether the postcollision convergence of India and Asia, estimated at >2;000 km (3, 4), was accommodated by homogeneous thickening or plate subduction (2). Global positioning systems (GPS) measurements have shown that at present an eastward motion dominates the surface deformation of northern and eastern Tibet (5). GPS and seismic anisotropy (6) indicate extrusion also of the deep Tibetan lithosphere to the east and southeast. Most surface wave studies revealed a thick lithosphere beneath much of the plateau (7-12), whereas body wave tomography observed the subducted Indian mantle lithosphere characterized by high wavespeed, in contrast to the Asian mantle lithosphere (13-15). Recently a high resolution P travel time tomographic study (15) imaged the high velocity Indian lithosphere in western Tibet below the entire plateau down to 300-400 km depth. In eastern Tibet, however, the front of the Indian plate is located south of the Yarlong-Zangbo Suture (YZS) (15). Relatively slow wave speeds are found in the upper mantle below the central and northeastern parts of the plateau. Modeling indicates that the Tibetan part of the lithosphere originated from the progressive accretion of a number of continental or island-arc type blocks before India came into direct contact with Asia (16) or stepwise subduction of the Asian pl...

We have obtained velocity images of the uppermost mantle beneath China by performing tomographic inversion of both Pn and Sn traveltimes. From the Annual Bulletin of Chinese Earthquakes, 99,139 Pn arrivals and 43,646 Sn arrivals were selected. Pn anisotropy was also obtained simultaneously with Pn velocity. Average Pn and Sn velocities are 8.05 and 4.55 km/s, respectively, and maximum velocity perturbations are about 3–4%. The Pn and Sn velocities are low in eastern China and high in western China. Particularly high velocities are associated with old basins (for example, Tarim, Junggar, Turpan‐Hami, Qaidam, and Sichuan) and stable craton (for example, Ordos). Low Sn velocities are found mainly throughout North China. In addition, velocities are relatively low beneath the central Tibetan Plateau and the North‐South Seismic Zone (along 103°E). In Tarim and central China where we observe strong anisotropy, the fast Pn velocity directions are consistent with the directions of maximum principal compressive stress as well as directions of crustal movement determined from Global Positioning System. Beneath the India‐Eurasia collision zone, the Pn anisotropy direction is parallel to the collision arc and nearly perpendicular to both the direction of maximum compression and crustal movement resulting from pure shear deformation. Both the velocity variations and anisotropy indicate that the Tibetan Plateau was extruded, and the mantle material beneath the plateau has flowed around the East Himalaya Syntax, while the remaining material has diverted northwestward beneath the Tarim Basin.

We analyze the teleseismic waveform data recorded by 42 temporary stations from the Y2 and ANTILOPE‐1 arrays using the P and S receiver function techniques to investigate the lithospheric structure beneath western Tibet. The Moho is reliably identified as a prominent feature at depths of 55–82 km in the stacked traces and in depth migrated images. It has a concave shape and reaches the deepest location at about 80 km north of the Indus‐Yarlung suture (IYS). An intracrustal discontinuity is observed at ~55 km depth below the southern Lhasa terrane, which could represent the upper border of the eclogitized underthrusting Indian lower crust. Underthrusting of the Indian crust has been widely observed beneath the Lhasa terrane and correlates well with the Bouguer gravity low, suggesting that the gravity anomalies in the Lhasa terrane are induced by topography of the Moho. At ~20 km depth, a midcrustal low‐velocity zone (LVZ) is observed beneath the Tethyan Himalaya and southern Lhasa terrane, suggesting a layer of partial melts that decouples the thrust/fold deformation of the upper crust from the shortening and underthrusting in the lower crust. The Sp conversions at the lithosphere‐asthenosphere boundary (LAB) can be recognized at depths of 130–200 km, showing that the Indian lithospheric mantle is underthrusting with a ramp‐flat shape beneath southern Tibet and probably is detached from the lower crust immediately under the IYS. Our observations reconstruct the configuration of the underthrusting Indian lithosphere and indicate significant along strike variations.

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Full suppression of type-I edge localized modes (ELMs) using n = 4 resonant magnetic perturbations (RMPs) as planned for ITER has been demonstrated for the first time (n is the toroidal mode number of the applied RMP). This is achieved in EAST plasmas with low input torque and tungsten divertor, and the target plasma for these experiments in EAST is chosen to be relevant to the ITER Q = 10 operational scenario, thus also addressing significant scenario issues for ITER. In these experiments the lowest neutral beam injection (NBI) input torque is around T NBI ∼ 0.44 Nm, which extrapolates to around 14 Nm in ITER (compared to a total torque input of 35 Nm when 33 MW of NBI are used for heating). The q 95 is around 3.6 and normalized plasma beta β N ∼ 1.5–1.8, similar to that in the ITER Q = 10 scenario. Suppression windows in both q 95 and plasma density are observed; in addition, lower plasma rotation is found to be favourabe to access ELM suppression. ELM suppression is maintained with line averaged density up to 60%n GW (Greenwald density limit) by feedforward gas fuelling after suppression is achieved. It is interesting to note that in addition to an upper density, a low density threshold for ELM suppression of 40%n GW is also observed. In these conditions energy confinement does not significantly drop (<10%) during ELM suppression when compared to the ELMy H-mode conditions, which is much better than previous results using low n (n = 1 and 2) RMPs in higher q 95 regimes. In addition, the core plasma tungsten concentration is clearly reduced during ELM suppression demonstrating an effective impurity exhaust. MHD response modelling using the MARS-F code shows that edge magnetic field stochasticity has a peak at q 95 ∼ 3.65 for the odd parity configuration, which is consistent to the observed suppression window around 3.6–3.75. These results expand the physical understanding of ELM suppression and demonstrate the effectiveness of n = 4 RMPs for reliable control ELMs in future ITER high Q plasma scenarios with minimum detrimental effects on plasma confinement.

The deep crustal deformation in the east Pamir in response to the Cenozoic collision with the Tien Shan and the Tarim Basin is so far poorly constrained. We present new insights into the crustal structure of the east Pamir and its surrounding regions using P receiver functions from 40 temporary and permanent seismic stations. The crustal thickness reaches a maximum of 88 km beneath the central and southern east Pamir and decreases sharply to 50–60 km along the southern Tien Shan and to 41–50 km below the Tarim Basin. The most prominent crustal structures involve a double Moho, suggesting eastward underthrusting of the Pamir lower crust beneath southern east Pamir, and two Moho offsets, supporting delamination of Asian lower crust below the central east Pamir and pure shear shortening along the northeastern margin between the Pamir and Tarim Basin.

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