The northeastern Tibetan Plateau (NE Tibet) is undergoing extensive outward expansion toward the Asian continent, generating significant intracontinental deformation. However, how the plateau and adjacent cratons respond to this process remains insufficiently understood. Here, we present refined three-dimensional P- and Swave velocity models of the crust and upper mantle beneath NE Tibet, which provide new constraints on plateaucraton interactions. Prominent velocity contrasts in the upper mantle between the plateau (low velocities) and the adjacent blocks (high velocities) suggest that the plateau expansion has been, to first order, impeded by the surrounding blocks. However, several dipping high-velocity anomalies in the upper mantle indicate that parts of the cratonic lithosphere may have been disrupted, possibly in response to the extruded mantle flow from the plateau. Furthermore, a normal-to-low velocity zone in the upper mantle beneath the Qinling Orogen may represent an asthenospheric channel for the eastward extrusion of the Tibetan asthenosphere. A vertically extensive low-velocity anomaly from the surface to similar to 600 km depth beneath the Yinchuan-Hetao Graben around the Ordos Block may reflect an upper-mantle plume related to the plateau expansion. Our study confirms that both the plateau and its surrounding regions have responded significantly to the plateau expansion process during the India-Asia continental collision.

As the most seismically active regions in the world, oceanic subduction zones show contrasting seismicity in different regions. To investigate the relationships among the thermal structure, metamorphism, deformation, and fluid activity of oceanic subduction zones, we summarized progress in numerical modeling of oceanic subduction zones, pressure and temperature paths of high- and ultrahigh-pressure metamorphic rocks and ophiolites, deformation of the subduction plate interface, seismic observations in subduction zones, and stabilities of hydrous minerals. The thermal structure of subduction zones not only controls depths of dehydration embrittlement of hydrous minerals, but also affects the mechanical coupling state of the subduction plate interface, eclogitization of the subducted oceanic crust, and phase transition of metastable olivine in the subducted lithospheric mantle. Dehydration embrittlement of hydrous minerals is the primary mechanism of intermediate-depth earthquakes in subduction zones. Earthquakes in warm subduction zones predominantly occur at shallow to intermediate depths, where most hydrous minerals dehydrate at depths of 80–160 km beneath the arc and the amounts of earthquakes decrease sharply below 160 km. By contrast, earthquakes in cold subduction zones distribute continuously to 300 km and hydrous minerals release water at greater depths. Nominally anhydrous minerals and dense hydrous magnesium silicates could carry water down to depths >300 km, resulting in localized water enrichment in the mantle transition zone. More experimental and seismic evidence is needed to decipher how fluid activity triggers slow earthquakes and deep-focus earthquakes. Knowledge about the origins of ophiolites and fossil earthquakes in ancient subduction zones will provide new insights into the tectonic evolution, the deep water cycle, and earthquake mechanisms of oceanic subduction zones.

High-resolution detection of hidden geological faults is vital for city planning, earthquake disaster prevention and large-scale engineering construction. This study deployed 229 short-period seismometers across a 10x30 km region within the Xianlin area of Nanjing. Of which, 199 formed a 2-D array and 30 formed a linear array. Various methods were applied to detect hidden faults in the study area. Using ambient noise tomography, a 3-D S-wave velocity structure was obtained from the surface to a depth of 6.0 km, allowing the first locations of a hidden fault to be mapped via velocity anomalies. A linear array was subsequently deployed based on these early findings, and the horizontal-to-vertical spectral ratio (HVSR) method was applied to estimate bedrock depth and define shallow fault features in greater detail. Finally, a shallow seismic exploration was performed to verify the detection results of ambient noise tomography and HVSR analysis. The results indicate the presence of a hidden fault in the study area, which manifests as a distinctive area of alteration in the high- and low-velocity anomalies in the 3-D S-wave velocity structure. Significant variation was identified in the sediment layer thickness in the shallow subsurface, as observed in the HVSR records. In addition, shallow seismic exploration defined important wave-group phase-axis discontinuities in areas with abrupt sedimentary thickness changes. Thus, the hidden fault identified in this study is a normal fault with a nearly north-dipping direction, dip angle of approximately 60 degrees and fault displacement of approximately 30 m. By linking these results with previous data, it is possible to suggest that such hidden faults are part of the Mufushan-Jiaoshan Fault. Future urban designs and buildings must thoroughly consider the seismic dangers in this region and apply suitable mitigation strategies.

The Tanlu Fault is a significant fault in East China that has been associated with numerous destructive earthquakes in its central-south segment. However, the mechanisms behind these earthquakes remain unclear. This study aims to shed light on the seismic velocity structures of the crust and upper mantle under East China and their influence on the region's seismotectonics. Our findings reveal that the upper mantle structures play a crucial role in regional seismotectonics. The 1668 Tancheng earthquake (M 8.5) is located above remarkable upper-mantle high-velocity bodies on both sides of the Tanlu Fault. Thus, it was likely produced by the interaction between the North China and Yangtze plates, with the lithospheric mantle significantly affecting the plate interaction. Another group of earthquakes of magnitude M 5-6 is located in the Subei-Yellow Sea Basin (SYSB). We have imaged a low-velocity body in the upper mantle, which is believed to represent hot and buoyant materials under the SYSB. This anonymous body may reduce the vertical stress in the crust and provide fluids to fault planes, thereby facilitating moderate-to-large earthquakes in the crust. These new findings provide valuable insight into the seismotectonics of East China, particularly the role of the upper mantle structures in shaping the region's seismic activity.

The Mongolian Plateau located between the Siberian Craton and the North China Craton developed after multiple tectonic evolutions. It is proposed to be related to the far-field effect of the Indo-Asian collision in the Cenozoic. In this study, we inverted for high-resolution S wave velocity structures of Mongolia using Rayleigh wave tomography to constrain the plateau evolution. In particular, we obtained crustal and upper mantle seismic structures under Gobi Desert by combining Mongolian and Chinese datasets. The study reveals strong low-velocity anomalies in the lower crust immediately beneath the Hangay Dome, while the low-velocity zones are imaged beneath the dome margins in the upper mantle. The results imply that the Hangay Dome was formed by mantle upwelling into the crust from major faults following lithospheric delamination. Under the South Gobi Desert, we imaged several inclined high-velocity patches in the upper mantle, indicating the subducted slabs formed in the Paleozoic. The ancient structures in the upper mantle led the Indo-Asian collision to propagate further to southern Mongolia.

Turkey has been undergoing compressional and extensional tectonics that greatly influences the major surface features following northward plate convergences since the Miocene. Despite increasing efforts in last few decades aiming to elucidate the current architecture of the crust and mantle beneath Turkey, several issues regarding the depth extent of the deformation zones, crust‐mantle interaction (e.g., coupling and decoupling) in relation to the deformation, and stress transmission in the lithosphere remain elusive. Inversion of 204,531 P wave arrival times from 8,103 local crustal earthquakes yields high‐resolution 3‐D P wave isotropic and azimuthal anisotropic velocity models of the crust and uppermost mantle beneath Turkey. Major outcomes of the present work are low‐velocity anomalies or velocity contrasts down to the uppermost mantle along the North and East Anatolian Fault Zones. We observe the fast velocity directions (FVDs) of azimuthal anisotropy in the lower crust and uppermost mantle parallel to the regional maximum extensional directions in western Turkey, whereas parallel to the surface structures in the crust and uppermost mantle beneath south-eastern Turkey. Our isotropic/anisotropic images strongly imply vertically coherent deformation between the crust and uppermost mantle in western and south-eastern Turkey. However, in central northern Turkey, the FVDs in the uppermost mantle are oblique to both the FVDs in the lower crust and the maximum shear directions derived from GPS measurements, suggesting that the crust and lithospheric mantle are decoupled.

Tectonics in Northeast Asia are characterized as the deep subduction of the Pacific Plate and the induced volcanism in Northeast China. Seismic anisotropy due to deformations is essential for understanding the mantle dynamics. However, the routine SKS splitting captures the accumulated seismic anisotropy from core‐mantle boundary to the surface, so the interpretation of the SKS splitting measurements is nonunique. Here, benefiting from abundant deep‐focus earthquakes in the subducting Pacific Plate, we measured shear wave splitting using both the SKS and local S waves recorded at Station MDJ to discriminate the anisotropy at different depths under Northeast China. We obtained 61 SKS and 22 local S wave splitting parameters. The SKS splitting measurements show apparent azimuthal variations that can be modeled by two‐layer anisotropy. The fast polarization directions (FPDs) of anisotropy in the upper and lower layers are NE‐SW and NW‐SE, which may be explained by the lithospheric deformation accompanying the Mesozoic fault activity and the asthenospheric deformation due to motion of the Eurasian Plate, respectively. The FPDs of the local S wave splitting measurements are parallel to the direction of the Pacific Plate subduction; the variation of the delay times is related to the take‐off angles. The observations can be explained by the inclined symmetry axis of the aligned metastable olivine in the subducting Pacific Plate.

The eastern margin of the Tibetan plateau is under ongoing expansion. Rise and growth of the Longmenshan are results of the interaction between the Songpan-Ganzi Terrane and the Sichuan Basin. In order to understand the block interactions in the eastern plateau margin, we studied the crustal structures using P wave receiver functions (including H-k staking, CCP stacking, and velocity inversion) with the waveforms recorded by 115 portable stations. The Moho, indicated by clear Ps phases, is generally deeper in the Songpan-Ganzi Terrane than in the Sichuan Basin, while a step is notable under the Longmenshan fault zone. We found a low velocity anomaly in the mid-lower crust below the Songpan-Ganzi Terrane and Longmenshan fault zone, which may imply the accumulated partial melting materials in the deep crust under the eastern plateau margin. Clear P-to-s converted phases are found within the crust of the Sichuan Basin. They look as apparent huge anticline structures, which may be caused by ancient crustal deformation under the stable craton.

Turkey has been undergoing compressional and extensional tectonics that greatly influences the major surface features following northward plate convergences since the Miocene. Despite increasing efforts in last few decades aiming to elucidate the current architecture of the crust and mantle beneath Turkey, several issues regarding the depth extent of the deformation zones, crust‐mantle interaction (e.g., coupling and decoupling) in relation to the deformation, and stress transmission in the lithosphere remain elusive. Inversion of 204,531 P wave arrival times from 8,103 local crustal earthquakes yields high‐resolution 3‐D P wave isotropic and azimuthal anisotropic velocity models of the crust and uppermost mantle beneath Turkey. Major outcomes of the present work are low‐velocity anomalies or velocity contrasts down to the uppermost mantle along the North and East Anatolian Fault Zones. We observe the fast velocity directions (FVDs) of azimuthal anisotropy in the lower crust and uppermost mantle parallel to the regional maximum extensional directions in western Turkey, whereas parallel to the surface structures in the crust and uppermost mantle beneath south-eastern Turkey. Our isotropic/anisotropic images strongly imply vertically coherent deformation between the crust and uppermost mantle in western and south-eastern Turkey. However, in central northern Turkey, the FVDs in the uppermost mantle are oblique to both the FVDs in the lower crust and the maximum shear directions derived from GPS measurements, suggesting that the crust and lithospheric mantle are decoupled.

The southeastern (SE) Tibetan plateau is uplifting accompanying strong seismicity, but the relationship between the crustal structure and tectonic process in this region is still unclear. Seismic anisotropy provides important clues for the deformation mechanism. Here we applied the harmonic decomposition approach and further conducted a Markov-Chain-Monte-Carlo (MCMC) inversion to analyze the crustal anisotropy from receiver functions using waveforms recorded by dense stations in the SE Tibetan plateau. More spatial details on the crustal anisotropy and interface are determined consequently. While the anisotropies in the upper crust are relatively weak (~2%), the anisotropies in the mid-lower crust are mostly stronger than 4%. The fast polarization directions (FPDs) in the mid-lower crust show a dominant circular pattern, in good coherence with the topographic contours, indicating that the crustal deformations in the SE Tibetan plateau may be mainly controlled by the gravity potential. Because of the significant Moho steps along the plateau margin, the extruded deep crustal materials are blocked by the strong crust around so that the minerals are aligned to be sub-parallel to the plateau margins.

The expansion of the Tibetan Plateau in its southeastern margin causes high seismic hazards in southwest China, even if some earthquakes are located far away from the expansion frontier in the southern Sichuan Basin. In this study, we determined the high-resolution P-wave velocity structure of the crust beneath the southern margin of the Sichuan Basin with an updated data set. We find low-velocity anomalies in the upper and lower crust whereas high-velocity anomalies between them; large earthquakes are spatially related to the low-velocity anomalies in the lower crust. The results indicate that the southern margin of the Sichuan Basin has been weakened laterally by the deep crustal extrusion related to the expansion of the SE Tibetan Plateau. We infer that the shallow crust might have been broken in association with the strike-slip faults during the plateau expansion, leading to large earthquakes.

深反射地震采集要获取地下深度超过30 km处的莫霍面信息,通常采用大药量炸药激发,炸药激发对生态环境影响较大,不符合绿色环保的勘探发展方向.本研究旨在探索采用可控震源实施深部探测的可行性,及与可控震源激发相匹配的最佳的接收方式.通过对辽东地区开展的可控震源和炸药激发对比试验分析表明,采用高精度可控震源EV56激发,SN5-5低频检波器2支串联的接收方式,可以获得较好的深层地壳结构图像.试验的成功,为后续采用可控震源进行深地地质探测提供了有效的科学依据,具有重要的实际参考价值.

We study the 3‐D P wave velocity structure of the crust and mantle down to 1,000‐km depth beneath the central and eastern United States. A 3‐D velocity model is obtained by conducting a joint inversion of 236,670 arrival times of local earthquakes and 870,455 relative traveltime residuals of teleseismic events recorded by the EarthScope/USArray Transportable Array. Significant low‐velocity (low‐V) anomalies are revealed in the crust beneath the eastern arm of the Midcontinent Rift and the Triassic Basins along the East Coast, whereas a prominent high‐velocity (high‐V) anomaly is visible beneath the Llano Uplift in central Texas. The stable North American Craton exhibits high‐V anomalies at depths of 65–250 km. Low‐V anomalies exist along the eastern and southern margins of the craton, which may reflect relatively thin lithosphere there. A prominent low‐V anomaly is revealed at depths of 50–200 km beneath the New Madrid Seismic Zone, which is bounded by high‐V anomalies to its southeast and northwest. This feature reflects a weak lithosphere surrounded by relatively strong cratonic regions and stress concentration caused intraplate seismicity in the New Madrid region. Two high‐V bodies appear in the mantle transition zone (410‐ to 660‐km depths) beneath the Interior Low Plateaus, the central Great Plains, and the Central Lowland, which may reflect the subducted Farallon plate or delaminated lithosphere. At depths of 800–1,000 km, a high‐V anomaly is visible beneath the southeast United States, which may be the subducted Hess Rise conjugate.

A high-resolution model of 3-D P-wave velocity (Vp) tomography of the crust in the source area of the 2016 Kumamoto earthquake (M 7.3) in West Japan is determined using a large number of arrival times of first P waves and reflected Pwaves from the Moho discontinuity (PmP). The PmP data are collected from original seismograms of the Kumamoto aftershocks and other local crustal events in Kyushu. Detailed resolution tests show that the addition of the PmP data can significantly improve the resolution of the crustal tomography, especially that of the lower crust. Our results show that significant low-velocity (low-V) anomalies exist in the entire crust beneath the active volcanoes, which may reflect the pathway of arc magma. The 2016 Kumamoto earthquake occurred at the edge of a small low-V zone in the upper crust. A significant low-V anomaly is revealed in the lower crust beneath the source zone, which may reflect the arc magma and fluids ascending from the mantle wedge. These results suggest that the rupture nucleation of the 2016 Kumamoto earthquake was affected by fluids and arc magma.

Objectives: Results of the relationships between dietary consumption of refined grains and the risk of stroke are mixed. This study was based on a meta-analysis of prospective cohort studies. Methods: We systematically searched the MEDLINE (from January 1, 1966) and EMBASE (from January 1, 1974) databases up to November 30, 2014. Random-effects models were used to calculate summary relative risks (SRRs) and 95% confidence intervals (CIs). Between-study heterogeneity was assessed using Cochran's Q and I-2 statistics. Results: Eight prospective studies (7 publications) with a total of 410,821 subjects and 8284 stroke events were included in the meta-analysis. Overall, a diet containing greater amounts of refined grains was not associated with risk of stroke, with no evidence of heterogeneity among studies (SRR = 1.02; 95% CI, .93-1.10; P-heterogeneity = .970; I-2 = 0). In addition, no significant associations between consumption of refined grains and risk of stroke were found for both women and men, for both hemorrhagic and ischemic strokes, and for both incident and fatal strokes. These null results are consistent with those of linear dose-response meta-analyses (SRR = .98; 95% CI, .73-1.03 for per 3 servings/day). Consumption of white rice was not associated with risk of stroke (SRR = 1.01; 95% CI, .93-1.11; P-heterogeneity = .966; I-2 = 0). Conclusions: The current meta-analysis provides some evidence for the hypothesis that consumption of refined grains was not associated with risk of stroke and its subtypes.

The Mayile ophiolitic mélange (MOM) is located in the southwestern part of the West Junggar (NW China) and forms part of the Southern Altaids. The MOM comprises ultramafic rocks, gabbro, pillow and massive lavas, abyssal radiolarian cherts and volcaniclastic rocks. Zircons with magmatic crystallization features including oscillatory zoning and high Th/U values from the isotropic gabbro within the MOM yield LA-ICP-MS U–Pb age of 572±9Ma (MSWD=1.0) marking the timing of crystallization of these rocks as late Neoproterozoic. Geochemically, the basalts of the corresponding gabbros from MOM display OIB-type alkali basalt and E-MORB-type tholeiitic basalt features. Both of these groups are characterized by LILE and LREE enrichment and HREE depletion, very weak or no Eu anomalies (Eu/Eu*=0.9–1), and no obvious Nb, Ta and Ti negative anomalies, suggesting a typical OIB affinity. We propose that these volcanic rocks were derived from a mantle plume-related magmatism associated with the evolution of the Paleoasian Oceanic system, with the mantle source containing 2%–5% garnet, ∼2% spinel and ∼2% amphibole. The basalts show within-plate affinity marked geochemical similarities with those from Hawaii and Xigaze seamount, suggestive of their intra-oceanic setting. Subduction of the oceanic lithosphere commenced during late Cambrian to early Ordovician, with the eventual accretion of the seamounts in the fore-arc together with oceanic fragments forming the Mayile ophiolitic mélange.