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High‐resolution seismic model is crucial for advancing our understandings on geological processes and enhancing seismic hazard mitigation programs. We construct a high‐resolution China Seismological Reference Model (CSRM‐1.0) in the top 100 km of the crust and uppermost mantle in continental China following a top‐down construction process. The employed seismic constraints include P‐wave polarization angle from tele‐seismic event, short‐period Rayleigh wave ellipticity from ambient noise, long‐period Rayleigh wave ellipticity from earthquake data, receiver function, empirical Green's function from ambient noise, Rayleigh wave phase/group velocity dispersion curves from regional earthquakes, and Pn‐wave travel time extracted from seismic data of 4,435 stations. CSRM‐1.0 has a spatial crustal resolution of ∼60 km beneath the north‐south seismic belt and trans‐North China orogen regions and ∼120 km beneath the rest of continental China, and a spatial mantle resolution of ∼300 km. CSRM‐1.0 exhibits prominent velocity heterogeneities in the crust and uppermost mantle and an eastward thinning of the crust, geographically correlating with geological settings. CSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution and improved model accuracy. Crustal composition inferred from CSRM‐1.0 exhibits a general transition from a felsic upper crust to a mafic lower crust. Mafic rocks in the lower crust are found predominantly along inter‐block boundaries and sporadically within the interiors of blocks, likely resulted from preferential inter‐block intrusions of magmas related to various oceanic plate subductions and the Emeishan mantle plume. This study contributes seismic constraints and CSRM‐1.0 to the CSRM product center (http://chinageorefmodel.org) as a backbone open‐access geophysical cyberinfrastructure. Plain Language Summary: High‐resolution seismic imaging of the crust and uppermost mantle offers crucial insights into regional geological histories and enhances seismic and volcanic hazard mitigation programs. We construct a high‐resolution China Seismological Reference Model (CSRM‐1.0) of the crust and mantle beneath continental China with various types of seismic constraints extracted from seismic data recorded by 4,435 stations deployed across continental China since 1990. CSRM‐1.0 has a spatial resolution of ∼60–120 km in the crust and 300 km in the uppermost mantle. CSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution and improved model accuracy. Crustal composition inferred from CSRM‐1.0 exhibits a general transition from a felsic upper crust to a mafic lower crust. Mafic rocks in the lower crust are found predominantly along inter‐block boundaries and sporadically within the interiors of blocks, likely resulted from preferential inter‐block intrusions of magmas related to various oceanic plate subductions and the Emeishan mantle plume. This study contributes seismic constraints and CSRM‐1.0 to the CSRM product center (http://chinageorefmodel.org) as a backbone open‐access geophysical cyberinfrastructure. Key Points: CSRM‐1.0 is constructed with various seismic constraints from data of 4,435 stations using a self‐consistent top‐down construction processCSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution, and enhanced model accuracyCSRM‐1.0 reveals major crustal mafic rocks related to the past subductions, an Emeishan mantle plume and geological inter‐block boundaries [ABSTRACT FROM AUTHOR]

The Tanlu Fault Zone (TLFZ) and Chifeng‐Kaiyuan Fault (CKF) serve as tectonic boundaries between the North China Craton (NCC) and the Central Asian Orogenic Belt (CAOB). Clarifying the refined structure of these tectonic boundaries is crucial for understanding the relationships between the tectonic units and the heterogeneity in the destruction of the NCC. In this study, two linear seismic arrays were deployed across these tectonic boundaries. Based on the phase velocity dispersion and receiver functions extracted from the seismic arrays, the Hamiltonian Monte Carlo algorithm was employed for the joint inversion of the S‐wave velocity (Vs) in the crust and uppermost mantle. The Vs model was then used to correct the time differences in common conversion point (CCP) stacking. The CCP stacking results indicate that the boundary faults TLFZ and CKF are both whole‐crustal faults that separate the NCC and CAOB. The Vs structure showed a significant low‐velocity anomaly in the mantle beneath the NCC, with intense seismic activity within the crust. This suggests that the NCC was affected by the subduction of the Western Pacific, leading to crustal and mantle destruction. In contrast, the CAOB exhibited a clear high‐velocity anomaly with relatively stable crustal structures. We believe that the NCC and CAOB have undergone structural modification and destruction due to the closure of the Paleo‐Asian Ocean and the activities of the TLFZ since the Late Mesozoic. During the Cenozoic, the region east of the TLFZ experienced more significant destruction in the NCC than the other adjacent tectonic units. Plain Language Summary: The joint inversion of Rayleigh wave phase velocities and receiver functions provides a reliable method for obtaining high‐precision S‐wave velocity (Vs) models. Here, we applied a joint inversion based on the Hamiltonian Monte Carlo algorithm to acquire detailed crust‐mantle Vs models in Northeast China and utilized this velocity structure to constrain the common conversion point (CCP) stacking to obtain a more reliable Moho depth. A comprehensive high‐resolution seismological model was established by integrating the Vs model, Moho depth, Vp/Vs ratio, and seismic activity. We then revealed the differential structural features and seismic heterogeneity on both sides of the tectonic boundaries between the Central Asian Orogenic Belt (CAOB) and the North China Craton (NCC). Our research results offer new constraints on the crust and upper mantle structure in Northeast China, contributing to the understanding of the geodynamic context underlying the differential structures between the CAOB and the NCC and the characteristics of their boundaries. Key Points: We obtained the fine crust‐mantle structure of tectonic boundaries in NE China using Rayleigh wave phase velocities and receiver functionsThe tectonic boundaries Chifeng‐Kaiyuan Fault and Tan‐Lu Fault are both whole‐crustal faults with strong seismic activityThe upper mantle of North China Craton exhibits low S‐wave velocity with strong seismic activity [ABSTRACT FROM AUTHOR]

Although ambient noise interferometry has been extensively utilized for seismic velocity tomography, its application in retrieving attenuation remains limited. This study presents a comprehensive workflow for extracting Rayleigh wave amplitude and attenuation from ambient noise, which consists of three phases: (1) retrieval of empirical Green's functions (EGFs), (2) selection and correction of amplitude measurements and (3) inversion of attenuation, site amplification and noise intensity terms. Throughout these processes, an 'asynchronous' temporal flattening method is used to generate high-quality EGFs while preserving relative amplitudes between stations. Additionally, a novel 't-symmetry' criterion is proposed for data selection along with the signal-to-noise ratio. Furthermore, 2-D sensitivity kernels are utilized to estimate the focusing/defocusing effect, which is then corrected in amplitude measurements. These procedures are designed to deliver reliable attenuation measurements while maintaining flexibility and automation. To validate the effectiveness of the proposed noise-based attenuation tomography approach, we apply it to a linear array, NCISP-6, located in NE China. The obtained results correlate reasonably well with known geological structures. Specifically, at short periods, high attenuation anomalies delineate the location of major sedimentary basins and faults; while at longer periods, a notable rapid increase of attenuation is observed beneath the Moho discontinuity. Given that attenuation measurements are more sensitive to porosity, defect concentration, temperature, melt and volatile ratio than seismic velocities, noise-based attenuation tomography provides important additional constraints for exploring the crustal and upper mantle structures. [ABSTRACT FROM AUTHOR]

We determined the velocity structure of the upper crust in the Jiaodong area using double difference seismic tomography, and found that the Jiaodong inland area near the surface (0–5 km) is mainly characterized by high-velocity anomaly, and there are several obvious low-velocity anomalies in the Bohai Sea. The Queshan metamorphic core complex shows obvious low-velocity anomaly at the depth of 5–15 km, and the southern part of the Linglong shows low-velocity anomaly at the depth of 10–20 km. It indicates the existence of significant mantle material upwelling and magmatic activity beneath metamorphic core complex. The Linglong and Queshan metamorphic core complex may be still in the process of uplift. The high-velocity anomaly of the Wulian-Yantai fault is likely closely related to the basic to ultrabasic rocks from the mantle. The basic to ultrabasic rocks upwelling along the Wulian-Yantai fault zone is segmented and mainly concentrated in the southern of the fault zone. [ABSTRACT FROM AUTHOR]

The Eastern South China Block (SCB) has experienced complex Mesozoic‐Cenozoic tectonism and intraplate volcanism. However, due to a lack of exhaustive exploration of the upper mantle's thermochemical structure, it is difficult to determine the extent of the lithospheric modification and the mechanisms by which the volcanism generate. Here, we jointly invert Rayleigh wave dispersion, surface heat flow, geoid height, and elevation data to provide a comprehensive thermal and compositional structure of the upper mantle beneath eastern SCB and infer regions of partial melting. Our model reveals widespread lithospheric thinning in the eastern SCB and large variations of lithospheric composition with a more fertile eastern Lower Yangtze lithosphere than the lithosphere elsewhere, suggesting the lithosphere of the eastern Lower Yangtze is more severely modified than the rest of the SCB. Moreover, two high‐temperature anomalies are revealed: one beneath the eastern Lower Yangtze and the other beneath the Pearl River Delta region, associated with the Pacific plate subduction and Hainan plume, respectively. The high‐degree partial melting (∼6%) in the asthenosphere beneath the Lower Yangtze is responsible for the strong ongoing lithospheric modification and the young intraplate volcanism in the Nvshan and Subei areas. Small‐scale upper mantle convections triggered by the large mantle upwellings created a low value of ∼3% melts, possibly responsible for the intraplate volcanism in the coastal CB and less severe lithospheric modification. We demonstrate that the lithospheric thickness and its thermochemical state are the key factors that influence the composition and evolution of intraplate volcanism in the eastern SCB. Plain Language Summary: The Eastern South China Block is an important part of the Eurasian plate, but we still don't know much about the lateral variations of its lithosphere composition and why it has intraplate volcanism. In this study, we use geophysical data to figure out the thermochemical structure of the lithosphere and sublithosphere and see if there is any partial melting. Our model shows that the lithospheric mantle beneath the eastern Lower Yangtze is more fertile, which means it has been recently rejuvenated like the North China Craton, while the lithospheric mantle beneath the Middle Yangtze and Cathaysia Block is more depleted, which means it still has an ancient cratonic mantle. We think that large‐scale upwelling of the mantle is causing high‐degree partial melting in the Lower Yangtze and small‐scale convection is causing low‐degree partial melting in the coastal CB. Finally, combining independent geochemical data from young basalts, we find that the lithospheric thickness and its thermochemical state are the key factors that influence the composition and evolution of intraplate volcanism in the eastern SCB. Key Points: We construct a thermochemical model and estimate the melt fraction beneath the eastern South China BlockThe thermochemical model reveals a fertile lithospheric mantle beneath the Lower Yangtze and a depleted one underneath the Cathaysia BlockThe origin and composition of intraplate volcanism are controlled by the lithospheric thickness and its thermochemical state [ABSTRACT FROM AUTHOR]

We presented two high‐resolution, three‐dimensional (3D) global P‐ and joint S‐wave velocity models of the whole mantle with a particular focus on the North Pacific realm using our new global tomographic inversion method. The 3D ray tracing based on data‐adaptive block parameterization was implemented to calculate ∼17 million body‐wave absolute travel times and ray paths of multiple classes (e.g., P, S, PP, SSS, PcP, ScSScS, Pdiff, and PKP) recorded by local networks in China, Alaska, and global stations. Rayleigh wave data at 40–250 s was also incorporated for resolution improvement. Compared to previous models, especially at long spatial wavelengths, our new models better exhibited rich variations in the properties of slabs and cratons subducting/subducted into the mantle. The Kurile‐Kamchatka‐Aleutian arc exhibits a distinct and well‐defined pattern of long linear bands characterized by high velocity (high‐Vp, high‐Vs) anomalies. These anomalies descend continuously from the subduction zone and then extend horizontally at the mantle transition zone (MTZ) beneath the Bering Sea, Japan Sea, or alternatively penetrate into the lower mantle below the Okhotsk Sea. We observed there was no slab‐related gap trapped on top of the MTZ beneath the Alaska Peninsula, which was possibly relevant for the subduction of the extinct Kula and Pacific Plates described in previous studies. A further unexpected discovery, deduced from the slab's location and tectonic history, was the identification of a high‐Vp anomaly running parallel to the plate boundary in the Aleutian forearc region, which was considered as an integral part of the Kula slab. Plain Language Summary: The Circum‐North Pacific contains an active North‐Northwestward subduction zone of the ancient Izanagi and Kula Plates and the present Pacific Plate during the Late Mesozoic to Cenozoic. This successive subduction system leads to complex plate tectonics characterized by substantial topographic variations, widespread subduction zones, abundant intraplate volcanic activities, and ancient craton lithospheric deformation. Here we image high‐resolution P‐ and S‐wave velocity models, which were inverted by our updated global tomographic method using data containing more than 17 million body and surface wave measurements. Our models indicate no gaps at the top of the mantle transition zone, and it differs from the previous studies beneath the Aleutian Arc. In addition, two parallel high‐Vp belts are imaged on both sides of the Aleutian Arc between ∼300 and 1,000 km depth, which were considered as part of the remnant Kula slab and present Pacific slab. These findings provide both a good understanding of the slab geometry and evolution associated with multiple plate subduction in the North Pacific subduction zone and an example to understand the way how the Earth's interior works. Key Points: Global P‐ and S‐wave tomography models were determined for the North Pacific by the joint inversion of body wave and Rayleigh wave dataMassive‐slab‐related high‐velocity anomalies revealed the geometries of the subduction slabs under the North Pacific realmTwo subparallel high‐velocity belts have presumably related to the subduction of the Pacific and Kula slabs [ABSTRACT FROM AUTHOR]

The Sichuan-Yunnan area is located at the southeastern margin of the Tibetan Plateau, where tectonic movement is strong with deep and large faults distributed in a staggered manner, which results in strong seismic activities and severe earthquake hazards. Since the 21st century, several earthquakes of magnitude 7.0 or above occurred in this region, which have caused huge casualties and economic losses, especially the 2008 Ms8.0 Wenchuan earthquake. At present, earthquake monitoring and source parameter inversion, strong earthquake hazard analysis and disaster assessment are still the focus of seismological researches in the Sichuan-Yunnan region. Regional high-precision 3D community velocity models are fundamental for these studies. In this paper, by assembling seismic observations at permanent seismic stations and several temporary dense seismic arrays in this region, we obtained about 7.06 million body wave travel time data (including absolute and differential travel times) using a newly developed artificial intelligence body wave arrival time picking method and about 100,000 Rayleigh wave phase velocity dispersion data in the period range of 5–50 s from ambient noise cross-correlation technique. Based on this abundant dataset, we obtained the three-dimensional high resolution Vp and Vs model in the crust and uppermost mantle of southwest (SW) China by adopting the joint body and surface wave travel time tomography method considering the topography effect starting from the first version of community velocity model in SW China (SWChinaCVM-1.0). Compared to SWChinaCVM-1.0, this newly determined velocity model has higher resolution and better data fitness. It is accepted by the China Seismic Experimental Site as the second version of the community velocity model in SW China (SWChinaCVM-2.0). The new model shows strong lateral heterogeneities in the shallow crust. Two disconnected low velocity zones are observed in the middle to lower crust, which is located in the Songpan-Ganzi block and the northern Chuandian block to the west of the Longmenshan-Lijiang-Xiaojinhe fault, and beneath the Xiaojiang fault zone, respectively. The inner zone of the Emeishan large igneous province (ELIP) exhibits a high velocity anomaly, which separates the two aforementioned low velocity anomalies. Low velocity anomaly is also shown beneath the Tengchong volcano. The velocity structures in the vicinity of the 2008 Ms8.0 Wenchuan earthquake, the 2013 Ms7.0 Lushan earthquake and the 2017 Ms7.0 Jiuzhaigou earthquake mainly show high Vp and Vs anomalies and the mainshocks are basically located at the transition zone between the high and low velocity anomalies. Along with the segmentation characteristics of seismic activity, we suggest that areas with significant changes in velocity structures, especially in active fault zones, might have a greater potential to generate moderate to strong earthquakes. [ABSTRACT FROM AUTHOR]

High-resolution seismic image is critically important for mining minerals. In this study, we collected seismic data from a local dense seismic array consisting of 154 stations around the Anyuan mining area and its adjacent region of Pingxiang City, Jiangxi Province in South China, and applied the ambient noise tomography (ANT) method to image the shear wave velocity structure in the study area. Shallow crustal velocities at depths less than 3.3 km were determined by direct inversion of Rayleigh wave group velocity dispersion curves at the period range of 0.5–5.0 s. Overall, the S-wave velocity structure has a tight correlation with surface geological and tectonic features in the study area. The shear wave velocity structure in the shallow crust of the Anyuan Mine and its adjacent areas displayed distinct low-velocity anomalies, which can be attributed to the depression of sedimentary structures and coal mining activities in the Pingxiang-Leping region. The zones surrounding the Anyuan fault (AYF) and Wangkeng fault (WKF) zones exhibited low-velocity anomalies from the ground surface to ~ 3.3 km underground. And the low-velocity anomalies at depths less than 1.2 km could be related to the sedimentary environment of coal mine and the coal mining activities, while the low-velocity anomalies at depths below 1.2 km are caused by the presence of fracture medium, oil and gas in the fault zone. The shear wave velocity changes sharply across the AYF, and the characteristics of the velocity change interface indicate that the AYF is inclined toward the northwest, with its extension reaching depths of approximately 3 km underground. [ABSTRACT FROM AUTHOR]

Icequakes associated with crevassing provide key information on stress fields and water flow pathways inside glaciers, conditions which are sensitive to temperature and precipitation. In this study, we analyse seismic data from 321 days recorded by five broad-band seismometers on Urumqi Glacier No. 1, Tianshan, China, to investigate the source characteristics of icequakes. We first apply a multidimensional autoregressive maximum-likelihood algorithm to detect 12 template events from 62 days of continuous waveform data. The centroid locations of the 12 template events are located using a grid-search approach. We then obtain a catalogue of 41   895 icequakes by compiling all seismic data through a template-matching method. The local magnitudes of all icequakes range between −3.3 and 0.5, with a completeness magnitude of −2.95 and Gutenberg–Richter b -value of 1.08. The particle motion and frequency contents of the 12 template events show that the dominant phases on the vertical component are Rayleigh waves at 5–40 Hz, suggesting that these icequakes were generated by near-surface crevasses. The average daily icequake number for each month and diurnal icequake variations show clear seasonal features. The icequakes may be related to growth of the surface crevasses due to additional melting water and precipitation in summer and to the thermal contraction of the ice body in winter. [ABSTRACT FROM AUTHOR]

The South China Craton formed after collision between the Yangtze and Cathaysia Blocks. The suture zone between these two blocks is the crux of understanding the geological evolution of South China. Due to the relative paucity of high-resolution subsurface data, the location of the suture zone in the southwestern region remains uncertain. To find the suture zone, we created a high-resolution model of the crust and upper mantle structure using 27 months of continuous waveform data acquired from 457 stations in South China. The model uses extracted phase velocity dispersion curves of Rayleigh waves at 4–40 s from ambient noise cross-correlation functions, to perform a direct inversion for an azimuthal anisotropic V SV model. In the crust a prominent belt of strong azimuthal anisotropy exists between the Yangtze and Cathaysia Blocks. The fast polarization axes in this belt correspond to the NE-trending orogen between the two blocks. In the deeper crust of the Cathaysia Block we image multiple areas of diffuse low-velocity anomalies. As defined by the margins of the strongly anisotropic belt, the Yangtze–Cathaysia suture zone is delineated by lines that traverse: Shaoxing–Jiangshan–Pingxiang–Longsheng–Hechi and Shitai–Jiujiang–Yueyang–Dayong–Jishou. Further analysis of the seismic data links deep low velocities with widespread Late Mesozoic magmatism in the Cathaysia Block. The deep low velocities are likely a result of dehydration of the subducting Pacific Plate causing mantle upwelling and underplating. [ABSTRACT FROM AUTHOR]

Internal structure imaging of the Earth, along with determining basin structure, can aid in evaluating potential seismic hazards. However, the high operating cost limits the current geophysical exploration methods; moreover, it is difficult to apply these techniques over a large area, which limits our understanding of the Quaternary structure and the development of earthquake prevention science. A combination of dense array observation technology and ambient noise surface wave tomography is being rapidly developed as a high-resolution urban detection method. Here, we report the ambient noise imaging results of a high-density array experiment. In the ambient noise surface wave tomography method (e.g., surface wave tomography; Eikonal tomography), the signal is assumed to be a single mode. However, several multimode signals were detected in this dataset. With the use of traditional methods to measure the dispersion, mode confusion occurs and the extracted dispersion curve jumps. To solve this problem, by combining the advantages of phase-matched filtering and dispersion compensation, we realized the automatic pickup of fundamental group velocity using reference phase velocity. From this, a Rayleigh wave group velocity map was obtained. The regional average phase velocity information was included in the inversion steps to reduce the uncertainty in the inversion of shear wave velocity. Finally, an S-wave velocity structure model was obtained within a depth of 500 m. The velocity structure was roughly layered and grew with depth. In the depth range of 240–320 m, obvious decreases in the S-wave velocity were observed. Compared with geothermal drilling data, this was speculated to be the reflection of a water-rich (confined water) sand layer. This study provides a technical approach for and a processing example of a high-density array, and its velocity model can be used as a reference for urban subsurface structure, underground space utilization, and earthquake disaster prevention and control. [ABSTRACT FROM AUTHOR]

The Gonghe Basin is one of the most important regions for the exploration and development of hot dry rock geothermal resources in China. However, there is still some controversy about the main heat source of hot dry rock geothermal resources in the Gonghe Basin. Combined with previous research results including three-dimensional magnetotelluric imaging and linear inversion of Rayleigh wave group and phase velocity result, we obtained a high-resolution underground spatial density distribution model of the Gonghe Basin based on satellite gravity data by using 3-D gravity focusing inversion method. According to the results, there are widely distributed low density anomalies relative to surrounding rock in the middle crust of the study area. The low-density layer is speculated to be a low-velocity, high-conductivity partial melting layer in the crust of the Gonghe Basin. The inversion result confirms for the first time the existence of a partial melt layer from the gravity point of view, and this high temperature melt layer may be the main heat source of the hot dry rock geothermal resources in the Gonghe Basin. It can provide a new basis for further research on the genesis of the hot dry rock geothermal system in the Gonghe Basin. [ABSTRACT FROM AUTHOR]

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The Pacific and Philippine Sea Plate subductions have resulted in and controlled the development of a typical trench‐arc‐back‐arc system in NE Asia since the Cenozoic. The formation of widely distributed intraplate volcanoes and the dynamic pattern of the entire region are still debated. Here we constructed a three‐dimensional anisotropic S‐wave velocity model of NE Asia by inverting Rayleigh wave dispersion using a modified reversible‐jump Markov Chain Monte Carlo (rj‐MCMC) algorithm. The resulting model revealed a localized mantle upwelling beneath intraplate volcanoes in NE Asia and an ongoing lithospheric downwelling beneath the central Korean Peninsula. This suggests vigorous asthenosphere and lithosphere interactions, which is likely to control the spatial distribution of Cenozoic volcanoes. The fast directions show clockwise rotation beneath NE Asia, which eventually points to the Nankai Trough. This observation is broadly consistent with shear wave splitting and suggests the presence of mantle flow from East China to the Philippine Sea Plate. The slab window beneath the Nankai Trough within the Philippine Sea Plate subduction system may accommodate the mantle flow from East China. Our study indicates that the interaction of the Philippine, Pacific Sea Plates, and Eurasian Plates plays an essential role in controlling the mantle flow and intraplate volcanism of NE Asia. Plain Language Summary: High‐resolution 3‐D anisotropic structure is critical to understanding the asthenospheric flow pattern and deep dynamics of active volcanoes. NE Asia experienced significant Pacific and Philippine Sea Plate subductions and extensive intraplate volcanism, although its dynamic causes are controversial. In this study, we obtained the three‐dimensional isotropic and azimuthal anisotropic S velocities of NE Asia by inverting surface wave dispersion data using a modified rj‐MCMC method. Our results revealed vigorous asthenosphere‐lithosphere interactions that control the evolution of intraplate volcanoes. The anisotropic pattern displayed a clockwise rotation beneath NE Asia, pointing to the Nankai Trough. Combining previous results of tomography and seismicity, our research indicated that at least part of the asthenosphere from East China flows to the Philippine Sea Plate through the slab window beneath the Nankai Trough. Key Points: A 3‐D anisotropic S‐wave velocity model of NE Asia is developed using a modified reversible‐jump Markov Chain Monte Carlo inversion methodWe reveal a localized upwelling beneath intraplate volcanoes and a lithospheric drip in the central Korean PeninsulaFast direction indicates asthenospheric flow from East China to the Philippine Sea Plate through the slab window beneath the Nankai Trough [ABSTRACT FROM AUTHOR]

The wave-induced local fluid flow mechanism is relevant to the complex heterogeneity of pore structures in rocks. The analysis of the local fluid flow mechanism is useful for accurately describing the wave propagation characteristics in reservoir rocks. In the exploration and production of hydrocarbon reservoirs, the real stratum may be partially saturated with a multi-phase fluid mixture in general. Therefore, it is of great significance to investigate the wave velocity dispersion and attenuation features in relation to pore structures and fluids. In this work, the characteristics of fabric microstructures are obtained on the basis of pressure dependency of dry rock moduli using the effective medium theory. A novel anelasticity theoretical model for the wave propagation in a partially-saturated medium is presented by combining the extended Gurevich squirt-flow model and White patchy-saturation theory. Numerical simulations are used to analyze wave propagation characteristics that depend on water saturation, external patchy diameter, and viscosity. We consider a tight sandstone from the Qingyang area of the Ordos Basin in west China and perform ultrasonic measurements under partial saturation states and different confining pressures, where the basic properties of the rock are obtained at the full gas saturation. The comparison of experimental data and theoretical modeling results shows a fairly good agreement, indicating that the new theory is effective. [ABSTRACT FROM AUTHOR]

A high‐resolution 3D crustal and upper‐mantle shear‐wave velocity model of Northeast China is established by joint inversion of receiver functions and fundamental‐mode Rayleigh wave phase velocities. The teleseismic data used to calculate receiver functions are collected from 107 CEA permanent sites and 118 NECESSArray portable stations. Rayleigh wave dispersion measurements are extracted from an independent tomographic study. Our model exhibits significant detail in S wave velocity structure. Particularly, we observe a nearly constant S wave velocity of 3.4–3.6 km/s from shallow to deep crystalline crust under the study area, which we attribute to a high thermal gradient. Some modestly positive S wave velocity anomalies in the crust beneath the Songliao basin are interpreted as solidified late‐Mesozoic mafic intrusions. In the upper mantle, we confirm the local presence of low‐velocity zones below the Changbai mountains and Lesser Xing'an mountain range, consistent with asthenospheric mantle upwelling models. Furthermore, moderately low shear velocities imaged beneath the Halaha and Abaga volcanoes indicate possible pathways of magma ascent through the lithospheric mantle from the asthenosphere. At a regional scale, the average lithosphere‐asthenosphere boundary depth increases from ∼70 km under the greater Changbai mountains to ∼100 km below the Songliao basin, and reaches ∼110–120 km beneath the Greater Xing'an mountain range in the west. The conjectured dense mantle lid under the Songliao basin, characterized by fast S velocities, may have prevented sublithospheric melts from migrating to the surface. Plain Language Summary: Northeast China is a unique region with a combination of ancient Precambrian geology, active seismicity, and volcanism. The presence of widely distributed volcanoes in this region is enigmatic and their origin has been widely debated. We use available seismic data to create a high‐resolution 3D shear‐wave velocity model for the crust and upper mantle of Northeast China. Our model reveals significant multiscale seismic velocity anomalies in the crust, mantle lithosphere and asthenosphere that we associate with the volcanic/magmatic processes. The lithospheric thickness gradually increases from ∼70 km beneath the Changbai mountains to ∼120 km some 1,000 km to the west. Our results provide novel constraints on the crustal and upper‐mantle structure of Northeast China and help to interpret the mechanism behind active volcanism and the geodynamic setting. Key Points: A nearly constant velocity in the crust may be due to a high thermal gradient and local high crustal velocities may denote mafic intrusionsLow S velocities are imaged in the upper mantle below the largest active volcanoes and locally the lithospheric mantle is thinned or absentThe lithosphere is ∼70 km thick below the greater Changbai mountains and thickens to ∼120 km under the Great Xing'an mountains in the west [ABSTRACT FROM AUTHOR]

As the two largest cratonic basins in China, the Ordos Basin and the Sichuan Basin are of key importance for understanding the evolutionary history of the Chinese continent. In this study, the shear-wave velocity (VS) structures of the shallow crust (depth up to 10 km) beneath the two basins are imaged based on the frequency-dependence of direct P-wave amplitudes in receiver functions. The teleseismic data used in the study came from 160 broadband seismic stations, including permanent and temporary stations. The results show that the VS and the thickness of the sediments in the Ordos Basin and the Sichuan Basin are respectively lower and thicker in the west than in the east. In the Ordos Basin, the shallow crustal VS increases gradually from 2.10 km s−1 in the northwest to 2.65 km s−1 in the southeast and the thickest sediments are 7–8 km in the northwest and 5 km in the east. In the Sichuan Basin, the shallow crustal VS increases from 2.4 km s−1 in the west to 2.7 km s−1 in the east and the thickness of the sediments decreases from >7 km in the west to 6 km in the east. The east-west difference of the shallow crustal structures of the two basins may have been controlled by the Cenozoic India-Eurasia collision. The western parts of the basins near the collision have a higher deposition rate, while in the parts inside the basins far from the collision, the VS slowly increases with depth, indicating that these areas have experienced a more uniform deposition process. In addition, both basins are characterized by velocity structures that are higher along the edges and lower inside of the basins. The edges of the basins suffered strong denudation due to the uplifting and deformation influenced by tectonic evolution. The downward gradient of the shear-wave velocity beneath the Ordos Basin is twice that of the Sichuan Basin, which may be caused by the different deposition and denudation rates of the two basins resulting from differences in structural evolution and thermal events. In addition, the northern Ordos Basin exhibits a strong structural horizontal stratification, while the southern part shows obvious lateral variations in the VS structure, both of which may have been affected by the Qilian orogenic event, the collision and assembly of the South China and the North China block, and the lateral extrusion of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Seismic anisotropy can be linked to different mechanisms, structures, and sources. We constrained the 3‐D depth‐dependent shear wave speed isotropic and azimuthally anisotropic structures with Rayleigh wave phase velocity from ambient noise in central Eastern China. We compared the results with other models and found that in the upper crust, the maximum horizontal stress direction differs mainly from the anisotropy that coincides with the strikes of major faults and geologic structures. We inferred that the anisotropy within proximity of faults might be related to fault fabrics, including fractures that strike parallel to the fast axes. The Tan‐Lu Fault controls the anisotropy in the crust to the uppermost mantle. The direction of fast axes in the fault zone is NNE‐SSW to N‐S, coinciding with the fault strike and trend that matches the fault shape on the surface. Southeastern North China craton has a weak anisotropy in the crust and uppermost mantle. The sources are possibly connected to the thrusting, tight trending folds, and dipping thrusts observed to be sub‐parallel to the Dabie Orogenic Belt (DOB). We propose that the NNE‐SSW Zhangbaling uplift group comes from the extension and ductile shearing in the Tan‐Lu Fault zone and the dragging of the northeastern South China Craton in the crust and the uppermost mantle. The N‐S polarized fast axes in the lower crust and uppermost mantle across the Sulu orogen and Xuzhou thrust‐and‐fold belt are the products of the resultant effect of subduction and deep Tan‐Lu faulting. Plain Language Summary: Seismic anisotropy is the dependence of seismic velocity of the medium on wave propagation direction. When observed, it gives information about the nature of material deformation. We used surface waves recovered from background noise to determine the anisotropy and its connection to the Tan‐Lu fault system, the largest fault system in Eastern China. Our results show that seismic anisotropy in the upper crust is likely caused by fault zone fabrics and the regional stress field. In the middle crust to the uppermost mantle, the anisotropy is parallel to the strike of the Tan‐Lu fault, indicating that the fault penetrates to the uppermost mantle and controls the anisotropy. The southeastern North China craton has weak anisotropy in the crust and uppermost mantle. The cause of anisotropy is likely the thrust faults resulting from compression that strike similar to the trend of the Dabie Orogenic Belt. The extension and shearing in the Tan‐Lu Fault zone is likely what caused the anisotropy at Zhangbaling uplift. The direction of anisotropy changes to N‐S in the north of the study region in the lower crust and uppermost mantle. The cause might be related to the resultant effect of subduction and deep Tan‐Lu faulting. Key Points: Azimuthal anisotropy in the crust and uppermost mantle deviates from stress, shear‐wave splitting, and absolute plate motion directionWithin proximity of regional faults, anisotropy might be related to fault fabrics including fractures that strike parallel to the fast axesThe direction of anisotropy coincides with the strike of the Tan‐Lu Fault signifying structural sources in the crust and uppermost mantle [ABSTRACT FROM AUTHOR]

The post-seismic history of the 2008 Mw7.9 Wenchuan earthquake shows that marginally stable deposits of large co-seismic landslide dams can pose persistent debris flow hazards for the downstream areas. Here, we combine analyses of single-station recordings of ambient noise with electrical resistivity tomography (ERT) surveys to explore the potential of drawing information on structure and geometry of the deposit of a large rock avalanche triggered by the Mw 7.9 2008 Wenchuan earthquake, which dammed the Yangjia stream in the Sichuan Province (China). The substantial thickness and heterogeneity of this kind of deposits limit the application of standard geophysical techniques, like active seismic surveys, which require highly energetic sources and long linear geophone arrays to reach adequate investigation depths. Passive single-station methods, relying on ambient noise recordings to determine site resonance properties, controlled by the contrast between soft surface layers and a stiffer substratum, offer the opportunity of investigating subsoil properties down to larger depths. In particular, we use a recently developed technique, which isolates the contribution of Rayleigh waves to ambient noise and draws information on sub-soil properties from the inversion of Rayleigh wave ellipticity curves plotted as function of frequency. In this framework, the ERT data can support the ellipticity curve inversion, typically affected by highly non-univocal solutions, by providing constraints for defining of the thickness of the uppermost surficial layers. The results allowed inferring the overlap of different layers within the 2008 rock avalanche deposit, as well as estimating lateral variations in their thickness and S-wave (Vs) velocities. [ABSTRACT FROM AUTHOR]

Using continuous data from a dense seismic array in Southwestern China, we tracked S‐wave microseism sources generated by two storms in Southeast Australia and the North Atlantic. In the frequency band 0.1–0.2 Hz, the beam strengths for SV‐ and SH‐wave sources can reach 29% and 18% of P‐wave, respectively. We found that the strong SH‐wave is only observed when the seismic sources are near the thick sedimentary regions whereas P‐ and SV‐wave is irrespective of that. It appears that in addition to a three‐dimensional structure that is needed for conversion from P‐wave to SH‐wave, amplitude enhancement by a sedimentary layer is essential for the detection of SH‐wave. Plain Language Summary: The interactions of ocean waves in the opposite propagation directions generate an equivalent vertical force in the ocean, creating dominant seismic noise in the frequency band 0.1–0.3 Hz. This forcing mechanism can explain the observations of P or Rayleigh waves but cannot explain the observations of SH or Love waves. In this study, from precise locations of SH‐wave sources in Southeast Australia and the North Atlantic, it is shown that SH‐wave sources are only found near a region of the thick sedimentary layer at the sea bottom. Amplification of waves in a thick sedimentary layer seems to be required to excite observable SH‐wave in seismic noise. Key Points: A large, dense seismic array in Southwestern China detects clean S‐wave signals in seismic noiseStrong S‐wave signals were tracked for the storms in Southeast Australia and the North AtlanticThe SH‐wave sources were only observed near thick sediment at the sea bottom, suggesting an amplitude enhancement by sediment is essential [ABSTRACT FROM AUTHOR]

This research studies the wave-ship interaction and green water induced by rogue waves. Superposition model is used for rogue wave generation, while a KVLCC2 model is selected as the target ship. Ship motions and impact pressures are obtained numerically, which agree well with the experimental measurements conducted at the State Key Laboratory of Ocean Engineering of China. It is found that the rogue wave can result in severe ship motion responses and impact loadings. The pitch angles and impact pressures at the bow induced by the rogue wave are 2–3 times greater than the average of the background wave train. Two types of green water events are observed, namely the Hammer-Fist (HF) event and the plus dam-breaking (PDB) event, the former of which leads to 3–4 times greater impact pressures than the latter. Additionally, interactions between rogue waves and the ship are further investigated within the ship speed range of 0–20 knots and the encounter angle range of 0–75°. The relationship between encounter frequency and impact pressures on the ship bow, side, stern, and deck induced by rogue waves is quantitatively analyzed, which has reference value as a benchmark for the consideration of rogue wave loadings. • Interactions between rogue waves and a KVLCC2 are studied experimentally and numerically. • Green water events induced by rogue waves are obtained and analyzed in three-dimensional. • Ship motions and impact pressures are obtained to provide a benchmark for the rogue wave and ship interaction. • Influence of encounter frequencies on green water events caused by rogue waves is discussed. [ABSTRACT FROM AUTHOR]

As urbanization grows at an unexpectedly rapid pace around the world, the underground space is gradually regarded as a largely undeveloped natural resource. Passive surface wave methods based on short-time traffic-induced noise measurements have been shown to be powerful tools for underground imaging and monitoring in urban areas. The common surface-wave investigations mainly focus on the use of Rayleigh waves in vertical components. We have developed an application of using three-component traffic-induced surface waves to investigate near-surface structures in Hangzhou City, Eastern China. With the deployment of two dense linear arrays along the orthogonal roads, we analyze the temporal and spectral characteristics of the three-component traffic noise. The retrieval of Rayleigh and Love waves using the horizontal components could be biased due to the uneven noise source distribution and errors in the orientation of the horizontal receivers. We use the match-field processing technique to obtain the direction of noise source distribution, and apply polarization analysis to evaluate the misorientation of the horizontal components. Subsequently, high-quality Rayleigh and Love waves are retrieved based on seismic interferometry within 1 h noise recordings. We invert the multicomponent surface waves to determine near-surface shear (S)-wave velocity structures. The joint analysis of Rayleigh and Love waves improves the reliability and stability of the result. Comparisons among the results from the individual inversion of Rayleigh waves, the joint inversion of Rayleigh and Love waves, and the logging data demonstrate that the jointly inverted S-wave velocity profiles provide better correspondence with the logging results, which confirms that the combined use of Rayleigh and Love waves from multicomponent traffic noise can be a more powerful technique for near-surface characterization in urban areas. • Developed an application using three-component traffic-induced surface waves to investigate urban near-surface structures. • We analyze the noise sources direction by MFP method and the misorientation of horizontal component by polarization analysis. • Combined use of Rayleigh and Love waves from traffic noise offers an efficient method for urban subsurface characterization. [ABSTRACT FROM AUTHOR]

Exploration of geothermal resources has become one of the major drivers for urbanization and economic transformation in southeast China, and it calls for temporal and spatial resolution improvements on conventional geophysical techniques under complex near-surface conditions. A dense seismic network including 192 sensors, with its aperture around 4.8 km, was deployed to record ambient noise for local-scale geothermal reservoir imaging in central Zhejiang Province, southeast China. With the ultrashort (less than 5 days) observation, a subset of the total station pairs was extracted to conduct seismic interferometry and dispersion measurements. This customized subnet was qualified to be an overdetermined system to achieve similar performance of entire network for the eikonal tomography with higher efficiency. The recorded high-frequency noise sources turned out to be rather homogeneous distributions, except for the dominant direction of northern Jinhua urban area. Azimuthal effects and wavelength restriction of dispersion measurements were quantified by simulating source–receiver responses under non-equipartitions of energy. The azimuth–velocity variations of field dataset verified that phase velocity measurements using the tested wavelength restriction were robust under different source–receiver orientations. The obtained phase velocity maps were comparable with the geological map. Furthermore, the inverted body wave velocities coincide well with the borehole data. Shear wave velocity profiles revealed corresponding fracture and depression structures of the reservoir. Finally, multiple geophysical properties delineate the shallow geothermy to be karst fissure water heated at certain earth temperature gradient. [ABSTRACT FROM AUTHOR]

We construct a high-resolution shallow 3-D seismic model in the top 10 km of the upper crust in the continental China, with constraints of P polarization, Rayleigh wave ellipticity and receiver function obtained from records of 3848 seismic stations. Our 3-D seismic model has a spatial resolution of 0.6–1.2° in the north–south seismic belt and the trans-north China orogen, and 1–2° in the rest of the continental China (except the Tarim basin and the southwest Tibet). The seismic model exhibits low velocity anomalies of deposits in major sedimentary basins and high velocity anomalies of crustal bedrocks in young orogenic belts and old tectonic blocks. The inferred sediment thickness maps display thick deposits in major sedimentary basins, some compacted sediments in the intermontane basins in young orogenic belts and little sediments in old tectonic blocks. We also discuss compaction effects of the sediments and implications of tectonic history and geological evolution of the major basins in the continental China based on the inferred seismic models. This study provides an effective mean of seismic imaging through joint inversion of various seismic constraints and establishes a framework of seismic data sharing for future studies in the seismological community in a first step of developing a China Seismological Reference Model. [ABSTRACT FROM AUTHOR]

Qinghai-Tibet Plateau is one of the regions with the strongest crustal tectonic movement in the world due to its special continental tectonic location. There are many large active faults in the block and its surrounding areas, which are prone to strong earthquakes. The area is also a natural test site for studying the mechanism of plate tectonic movement in the continent. Global Positioning System(GPS)is widely used in the study of crustal deformation monitoring due to its high temporal and spatial resolution, wide coverage, and high observation accuracy. The high-resolution GPS crustal movement velocity field obtainedby China crustal movement observation network(CMONOC-Ⅰ)and China continental tectonic environment monitoring network(CMONOC-Ⅱ), has clearly revealed the crustal tectonic movement and deformation of Qinghai-Tibet Plateau in the past 20 years. The research progress of current crustal movement and deformation characteristics of Qinghai-Tibet Plateau was systematically summarized based on GPS monitoring data, and the GPS data sources, and high-precision data processing methods and strategies for monitoring the crustal movement of Qinghai-Tibet Plateau were reviewed. The influence of different reference data on the processing results of GPS velocity field was discussed, and the current analysis models for crustal movement and deformation of Qinghai-Tibet Plateau were comprehensively explained from kinematics and dynamics. The current tectonic movement and deformation characteristics were deeply analyzed from both the shallow and deep of Qinghai-Tibet Plateau based on the calculations of integrated model. From the perspective of tectonic dynamic mechanism of plate movement, the current regional dynamics background of Qinghai-Tibet Plateau and the uplift mechanism of the mount Qomolangma region under its influence were interpreted in detail. Finally, the results of crustal movement and deformation of Qinghai-Tibet Plateau using GPS technology were summarized, and the important development trend of crustal deformation monitoring of Qinghai-Tibet Plateau in the future was also prospected. [ABSTRACT FROM AUTHOR]

In this study, we report a first major effort to measure surface wave amplitudes and to map attenuation structures of the Chinese mainland with dense modern broadband seismic networks in the country. We developed a method of phase‐matched filtering to automatically extract fundamental‐mode Rayleigh waves and to measure the spectral amplitudes. The results are compatible with those from the previous manual method with great improvement in efficiency. Using the automatic method, we extracted a large quantity of the amplitudes of Rayleigh waves at periods of 10 and 20 s recorded by 141 broadband stations from the China Digital Seismograph Network and 656 broadband stations from the China Regional Seismic Network. We performed tomographic inversions using the method of two‐station amplitude ratios and obtained images of the surface wave attenuation maps at periods of 10 and 20 s for the Chinese mainland. The tomographic model resolution reaches 1–2° in central and eastern China, 3–5° in western China, and 5° in the southeastern margin of the Tibetan Plateau and northeastern China. The tomographic results demonstrate good correspondence with geological structures. The distribution of strong historical earthquakes indicates that in the Chinese mainland, these earthquakes occurred mainly in high‐attenuation areas or the junctions between high‐ and low‐attenuation areas. Key Points: A first major effort was made to map surface wave attenuation structures of the Chinese mainland using dense networks of stationsAn automatic method was developed to extract the fundamental‐mode Rayleigh waves with great improvement of efficiencyThe attenuation maps show important geological structures, correlation with seismicity, and similarity and contrast with seismic velocity [ABSTRACT FROM AUTHOR]

Knowledge about the spatial contact relationship between the Yangtze Plate and the eastern Qinling-Dabie orogenic belt can not only provide a scientific basis for the exploration of mineral resources, disaster prevention and earthquake prediction in the region, but also play an important role in reconstructing the geological process of the central orogenic belt. Hence, high-resolution lithospheric velocity model is essential to address these geological problems. In this study, using waveform data from 48 stations in Hubei Province and adjacent regions, central China, we invert for a 3-D S -wave velocity structure model of the crust and upper mantle from Rayleigh wave tomography. Our model reveals the complex subduction pattern of the Yangtze Plate to the north and the thrust-nappe tectonics of the Qinling-Dabie orogenic belt along the Mianlue suture with different scales and different deformation strengths. In addition, in the central part of Hubei Province, the local Yangtze slab has been broken into several pieces, among which the upwelling low-velocity anomalies appear. Moreover, the southern margin of the Dabie orogenic belt has undergone thrusting-nappe movement, and a series of associated structures are formed in the northern margin of the middle Yangtze platform. The contact zone between the two blocks in this area is composed of a series of thrust faults with dextrorotation slip component. Finally, based on the 3-D S -wave velocity image of Hubei Province and its vertical cross-section profiles along three different directions, three dynamic models are proposed to explain the spatial contact relationship between the Yangtze Plate and the eastern Qinling-Dabie orogenic belt in different regions. [ABSTRACT FROM AUTHOR]

Southwest (SW) China is located in a transition site from the active Tibetan Plateau to the stable Yangtze craton, which has complicated tectonic deformation and severe seismic hazards. We combine data from ambient noise, teleseismic body and surface waves, and petroleum wells and seismic-reflection profiles to better constrain the crustal shear velocity structure in SW China. We jointly invert the Rayleigh wave dispersion (5–40 s period), Rayleigh wave ZH ratio (20–60 s period), and P -wave receiver function for 114 permanent stations with a stepwise linearized joint inversion method. Compared to previous tomography results, we observe higher shear velocity in the sedimentary rocks within the Sichuan Basin, which is consistent with sonic logging measurements. Our model reveals widespread low-velocity zones in the mid-lower crust, and their boundaries correlate well with major fault systems. Between two main mid-crustal low-velocity channels, a prominent high-velocity region surrounded by earthquakes is observed in the inner zone of the Emeishan large igneous province (ELIP) and around the Anninghe-Zemuhe fault zone. These observations are comparable to regional tomography results using very dense arrays. Based on the results, we suggest that mid-lower crustal ductile flow and upper-crustal rigid fault movement play equally important roles in controlling the regional deformation styles and earthquake distribution in SW China. Our results also resolve thick crust–mantle transition zones beneath the eastern Tibetan Plateau and the inner zone of the ELIP due to 'top-down' and 'bottom-up' crust–mantle interactions, respectively. Our new model can serve as a reference crustal model for future high resolution model construction in SW China. [ABSTRACT FROM AUTHOR]

Urban geophysics ups the ante in the world of applied geophysics, which requires innovative thinking and seemingly off-the-wall approaches, if for no other reason than the settings. Ambient-noise-tomography (ANT) can play a pivotal role in yielding subsurfa2ce information in urban areas, which is capable of dealing with challenges related to these scenarios (e.g., human activities and low signal-to-noise ratio). In this study, the ANT was conducted to investigate the near-surface shear-velocity structure in the surrounding area of the Baotu Spring Park in downtown Jinan, Shandong Province, China. Quiet clear Rayleigh waves have been obtained by the cross-correlation, which indicates that strong human activities, such as moving vehicles and municipal engineering constructions, can produce approximately isotropic distribution of noise sources for high-frequency signals. The direct surface-wave tomographic method with period-dependent ray-tracing was used to invert all surface-wave dispersion data in the period band 0.2-1.5 s simultaneously for 3D variations of shear-velocity (Vs) structure. Our results show a good correspondence to the geological features with thinner Quaternary sediments, the geological structural characteristic of the limestone surrounded by the igneous which has the highest velocity than that of the limestone in the study area, and several concealed faults of which specific location has been detected at depth. The results demonstrate that it is possible to successfully use ANT with high-frequency signal in an urban environment provided a detailed planning and execution is implemented. [ABSTRACT FROM AUTHOR]

The collision of the North China and Yangtze blocks, along with multiple orogenic movements, has caused complex tectonic deformation of the lithosphere in Hubei Province. In order to reveal the stress distribution features and tectonic deformation mechanisms of the regional lithosphere, we inverted an azimuthal anisotropic structural model of the Hubei lithosphere from anisotropic Rayleigh wave tomography with data obtained from 48 broadband seismometers deployed in and around the province. Our model revealed strong lateral variations of azimuthal anisotropy in the crust and upper mantle, providing new seismological evidence for the lithospheric modification of the Yangtze block and the layered deformation of the lithosphere east of the North-South Gravity Lineament. We speculate that the primary dynamic factor causing lithospheric modification in the Yangtze block is related to the rifting events associated with the super-mantle plume, triggered by the deep subduction of the Pacific and Philippine plates. Meanwhile, the rifting event is also the main cause of the lithospheric structural layered deformation east of the North-South Gravity Lineament. The inverted anisotropic model, together with the results of previous geodetic and seismologic studies, revealed the causes and tectonic deformation mechanisms of anisotropy generation in the crust and upper mantle in Hubei Province. Crustal deformation in the Hubei region may be related to the eastward expansion of materials from the Tibetan Plateau and the ultra-high pressure metamorphic zone formed by the subduction and collision of the Yangtze and North China blocks, while upper mantle deformation is associated with subduction and collision of Yangtze and North China blocks, preserved fossil anisotropy from previous orogenic movements, and rifting events tied to the super-mantle plume induced by the deep subduction of the Pacific and Philippine plates. Moreover, we analyzed the regional crust-mantle coupling mechanism and concluded that the crust-mantle in the Dabie orogenic belt is coupled, whereas it is decoupled in other regions. • An azimuthal anisotropic model is built for the crust and upper mantle of Hubei Province. • Anisotropic model provides new seismic evidence for lithospheric modification of the YZB. • We observed the layered deformation of the lithosphere east of the NSGL. • Anisotropic causes and tectonic deformation mechanisms of the Hubei lithosphere are revealed. [ABSTRACT FROM AUTHOR]

The Middle-Lower Yangtze River Metallogenic Belt (MLYMB) is an important mineral resource region in China. High-resolution crustal models can provide crucial constraints to understand the ore-forming processes and geodynamic setting in this region. Using ambient seismic noise from 107 permanent and 82 portable stations in the MLYMB and the adjacent area, we present a new high-resolution 3D S-wave velocity model of this region. We first extract 5–50 s Rayleigh wave phase velocity dispersion data by calculating ambient noise cross-correlation functions (CFs) and then use the surface wave direct inversion method to invert the mixed path travel times for the 3D S-wave velocity structure. Checkerboard tests show that the horizontal resolution of the 3D S-wave velocity model is approximately 0.5°–1.0° and that the vertical resolution decreases with increasing noise and depth. Our high-resolution 3D S-wave velocity model reveals: (1) A V-shaped high-velocity zone (HVZ) is located in the lower crust and the uppermost mantle in the study region. The western branch of the HVZ passes through the Jianghan Basin, the Qinling-Dabie orogenic belt and the Nanxiang Basin. The eastern branch, which almost completely covers the main body of the MLYMB, is located near the Tanlu Fault. The low-velocity anomalies between the western and eastern branches are located in the area of the Qinling-Dabie orogenic belt. (2) High-velocity uplifts (HVUs) are common in the crust of the MLYMB, especially in the areas near the Tanlu Fault, the Changjiang Fault and the Yangxin-Changzhou Fault. The intensities of the HVUs gradually weaken from west to east. The V-shaped HVZ in the lower crust and uppermost mantle and the HVUs in the middle and lower crust likely represent cooled mantle intrusive rocks. During the Yanshanian period, fault systems formed in the MLYMB due to the convergence between the South China Plate and the North China Plate, the multiple-direction drifting of the Paleo-Pacific Plate and its subduction beneath the Eurasian Plate. The dehydration of the cold oceanic crust led to partial melting in the upper mantle. Temperature differences caused strong convection of the upper mantle material that underplated the lower crust and rose to near the surface along the deep fault systems. After mixing with the crustal materials, mineralization processes, such as assimilation and fractional crystallization, occurred in the MLYMB. [ABSTRACT FROM AUTHOR]

In this study, on the basis of absolute first-arrival times of 84756 P- and S-waves from 6085 earthquakes recorded at 56 fixed stations in Yibin and surrounding areas in China from January 2009 to January 2019, focal parameters and three-dimensional (3D) body-wave high-resolution velocity structures at depths of 0–30 km were retrieved by double-difference tomography. Results show that there is a good correspondence between the spatial distribution of the relocated earthquakes and velocity structures, which were concentrated mainly in the high-velocity-anomaly region or edge of high-velocity region. Velocity structure of P- and S-waves in the Yibin area clearly shows lateral inhomogeneity. The distribution characteristics of the P- and S-waves near the surface are closely related to the geomorphology and geologic structure. The low-velocity anomaly appears at the depth of 15–25 km, which is affected by the lower crust current. The Junlian-Gongxian and Gongxian-Changning earthquake areas, which are the two most earthquake-prone areas in the Yibin region, clearly differ in earthquake distribution and tectonic characteristics. We analyzed the structural characteristics of the Junlian-Gongxian and Gongxian-Changning earthquake areas on the basis of the 3D body-wave velocity structures in the Yibin region. We found that although most seismicity in the Yibin area is caused by fluid injection, the spatial position of seismicity is controlled by the velocity structures of the middle and upper crust and local geologic structure. Fine-scale 3D velocity structures in the Yibin area provide important local reference information for further understanding the crustal medium, seismogenic structure, and seismicity. [ABSTRACT FROM AUTHOR]

Situated in a transition zone between the Ordos basin and the Huabei basin, the Trans-North China Orogen (TNCO), or the central North China Craton, evolved as an extensional orogen during the late Mesozoic to Cenozoic, with Fenhe-Weihe Rift (FWR) developing in it in the Cenozoic. In this study, we construct a high resolution lithospheric model of TNCO by jointly interpreting the broadband surface wave dispersions derived from ambient noise and teleseismic surface wave data. The most significant features of the lithospheric mantle are the two separated low velocity anomalies beneath the northern and southern TNCO respectively. Considering that the Pacific slab subducted to the mantle transition zone with a gap under the Datong volcanic zone, and large-scale low-velocity mantle materials are ascending from the lower mantle through the slab gap, which is evidenced by teleseismic P wave tomography, we propose here that the northern TNCO was affected by the mantle upwelling from the lower mantle. On the contrary, the south TNCO was mainly modified from the dehydration reaction process of the stagnant Pacific slab. In the lower crust, we observe significant low velocities beneath the Datong volcanic field, which are interpreted as the recent magmatic underplating resulted from the ongoing mantle upwelling in the northern TNCO. In addition, the mantle upwelling has dominated the rifting process in the northern segment of the FWR. Although the passive rifting of the FWR propagated from south to north, the north FWR is under an active lithosphere thinning regime now. • High-resolution S wave velocity model of TNCO inverted from broadband Rayleigh wave dispersions. • Different causes for lithospheric LVZs in north and south TNCO and On-going lithospheric modification in the TNCO. • Transition from passive to active rifting in the northern segment of the FWR [ABSTRACT FROM AUTHOR]

The Passive Multichannel Analysis of Surface Waves (MASW) method is a non-intrusive and cost effective technology adopted in civil and earthquake engineering for site geological and geotechnical survey. However, the application of passive MASW method under urban environments meets some challenges. One of interesting problems is associated with underground railways, which can be treated theoretically as buried sources. Since Rayleigh wave energy is dominant among that of surface waves, it is critical to design a proper geophone configuration during field tests at a site close to the metro line to ensure significant Rayleigh wave energy and therefore reliable dispersion images. This paper studied the propagation of Rayleigh waves generated from a buried source and proposed an empirical formula to estimate the nearest offset, which was then verified by numerical simulations. A case study was implemented in Shanghai, China at a site close to a subway line. With a linear spread geophone configuration, the influence of different parameters, including nearest offset, spread length and geophone interval, was investigated regarding their influences on dispersion images. Field tests were conducted by following the geophone configuration designed based on the proposed estimation method. The one dimensional (1D) shear velocity structure, being inverted from field vibration measurements, matches relatively well with the geologic feature obtained from borehole testing. Study results are expected to help facilitate the application of the passive MASW method for cases in which Rayleigh waves are generated by the buried source like underground traffics in cities. • Near-field effects due to subway traffic were studied for surface wave method application. • A method was proposed for the nearest offset estimation in MASW test with buried sources. • A case study was performed at a site close to underground railway for validation. [ABSTRACT FROM AUTHOR]

The subcutaneous implantable cardioverter-defibrillator (S-ICD) may provide comparable protection while avoiding the disadvantage of transvenous lead, but the abnormal features of the hypertrophic cardiomyopathy (HCM) electrocardiogram (ECG) make it a challenge for S-ICD template screening. We aimed to investigate S-ICD eligibility according to the S-ICD manufacturer's surface ECG screening template in China, and further analyze its corresponding ineligible predicting factors in 12-lead suface ECG. A total of 179 HCM patients (114 males; mean age: 45 ± 14 years) underwent S-ICD screening at rest and on exercise, among which 91 patients (50.8%) were eligible for S-ICD. Among the patients who passed screening, 43 (47.3%) had 3 vectors eligibility; 64 (70.3%) screening qualified on both sides; 10 patients (11.0%) passed the screening while the electrodes located only on the left parasternal line versus 17 patients (18.7%) moved to the right line. The secondary sensing vector (Lead III) was mostly appropriate (53.6%), followed by the primary sensing vector (lead II, 53.1%) and the alternate sensing vector (Lead I, 46.9%). Higher R wave was the major cause, accounted for 70.5%, for screening failure. There existed significant difference in T wave in lead II, aVF, V5 and V6, adds R/T ratio in lead V5 and V6, between the screening success group (group A) and screening failure group (group B) at rest and on exercise. A multivariable logistic regression analysis was performed to identify that R/T ≤ 3.5 in lead V5 was the independent factor to predict the screening ineligibility, with odds ratio 3.648. S-ICD screening success is 50.8% in HCM patients, which is much lower than that in other studies. R/T ≤ 3.5 in lead V5 in 12-lead surface ECG was an independent predicting factor for screening failure. [ABSTRACT FROM AUTHOR]

Ambient noise tomography (ANT) has been used successfully to image shallow earth structure. Here we perform ANT on a local dense seismic array around the Tanlu fault zone (TFZ) to the southeast of Hefei City, Anhui Province in eastern China. The array consists of 53 stations with average spacing close to 5 km. Cross-correlations of vertical-component ambient noise data of different station pairs are computed in 1-h segments and stacked over 1 month from 17 March to 26 April 2017. Clear fundamental-mode Rayleigh waves are observed between 0.2 and 5 s period. We then use the direct surface-wave tomographic method with period-dependent ray tracing to invert group and phase dispersion travel-time data simultaneously for three-dimensional (3D) shear-wave velocity (Vs) structure. The Vs model shows clear correlation with the known geologic features. The TFZ is associated with a high-velocity anomaly zone in the shallow crust, corresponding to metamorphic rocks due to magma intrusion. Low-velocity anomaly zones are mainly located to the west of the TFZ, caused by thick sedimentary layers in the Hefei Basin. Our study shows that, with ambient noise data recorded on a dense array and an advanced surface-wave inversion method, we can image detailed structure around the fault zone. [ABSTRACT FROM AUTHOR]

The southern margin of the Ordos Basin is covered by thick loess sediments. This area is typically characterized by frequent geologic hazards and is rich in energy resources. Identifying the velocity structure of the loess layer is of great significance for geologic hazard prevention and resource explorations in this area. In this paper, we utilize Rayleigh-wave data for imaging the shear-wave velocity (vs) of the loess sediments in the Dongjiahe area, in the southern margin of the Ordos Basin. The data collected in the Dongjiahe area is dominated by the higher-order mode Rayleigh-wave; the dispersive energy of the fundamental mode Rayleigh-wave is weak and suppressed in some frequency bands. An improved frequency–wavenumber (F-K) transform method which can enhance the dispersive energy and expand the frequency range of the weaker fundamental (or higher) mode Rayleigh-wave is proposed in this paper. Numerically simulated data are first utilized to show the processes and effectiveness of the improved F-K transform method. Then, we utilize the improved F-K transform to generate multi-mode dispersive spectrums and extract dispersion curves of the real-world data collected in the Dongjiahe area. Dispersion curves are inverted for vs structure using the Levenberg–Marquardt method. The pattern of the two-dimensional vs section of the study area indicates that the loess sediments mainly distributes as approximate flat layers with vs gradually increasing as the depth increases. In addition, the results also reveal the bedrock depth of some parts of the survey line. [ABSTRACT FROM AUTHOR]

Abandoned coal tunnels (ACTs) pose risks to coal mine safety by accumulating gas and water, causing surface subsidence, and endangering infrastructure. Accurate detection of ACTs is vital for advanced prediction and geotechnical hazard warnings. Seismic methods, particularly the surface-wave method, have demonstrated reliability in detecting shallow buried tunnels within complex geological environments, but improvements in accuracy and resolution are still needed. In this paper, we suggest utilizing the multiscale window analysis of surface waves (MWASW) method for ACT surveys. We conduct a synthetic test and a real-world case study to evaluate the feasibility and validity of this approach. The synthetic test on a 2D ACT model reveals that MWASW can reconstruct anomalous structures and identify the presence of an ACT, while also highlighting some limitations of the method. In a real-world scenario, we applied MWASW to a multi-survey line dataset from a coal mine in Shanxi Province, China. The resulting meter-scale resolution pseudo-3D S-wave velocity structure uncovers a primary ACT and two sub-ACTs buried at approximately 60 m, offering valuable insights into their morphology and orientation. To our knowledge, this is the first application of the MWASW method in such a case study, indicating its potential as an emerging alternative for characterizing complex near-surface media, such as abandoned coal tunnels or mined-out areas in coal fields. • Detect coal tunnels using spatial multiscale dispersion analysis method. • Directly reveal 2D S-wave velocity profiles with high resolution and accuracy. • Reconstruct a pseudo-3D structure model in field case. [ABSTRACT FROM AUTHOR]

Investigating mechanisms and characteristics of the non-tectonic deformation has crucial implications for evaluating the subsurface stress evolution. In this study, we continuously tracked the seasonal velocity changes of Rayleigh wave at 2–10 s with the ambient noise interferometry and discrete wavelet decomposition, in different regions along the actively deforming North–South Seismic Belt (NSSB) and the stable Guangdong region in the South China block in China. The seasonal velocity changes exhibit strong lateral variations across different regions, with much larger seasonality (annual periodicity) and amplitude along the NSSB than those in the stable Guangdong region. There are also small-scale lateral variations inside of each region and generally larger amplitudes of the seasonal velocity changes at greater depth, but the phases (peaks, mostly in winter or summer) at different depths are consistent. The mechanism of the seasonal changes is most likely the direct loading effect of the precipitation, as indicated by consistency in their phases. However, the amplitudes of the seasonal velocity changes seem not controlled by the amount of precipitation, but are more dependent on the tectonic deformation at the different scales, from the correlation between the amplitude of the velocity change and the absolute strain rate. We demonstrate that the crustal media in the regions with larger tectonic background stress are more sensitive to the seasonal loadings. The new finding also highlights the role of the external seasonal loadings in the modulation of seismic activities and risk evaluations. • Seasonal seismic velocity variations are found in different regions in China, likely from direct hydrological loadings of precipitation. • The spatial pattern of the seasonal velocity changes is consistent with the distribution of tectonic deformation at multi-scales. • The amplitude of the seasonal velocity changes is more dependent on the magnitude of local deformation than the amount of precipitation. • Seasonal velocity changes are observed in the North–South Seismic Belt. • Loadings from precipitation induce the seasonal fluctuations. • Tectonic deformation controls the amplitudes of the seasonal changes. [ABSTRACT FROM AUTHOR]

Accurate characterization of the low-velocity anomalies such as utility tunnels in the near-surface by effective geophysical imaging methods has been a valuable but challenging task for urban hazard assessment, underground space development and infrastructure construction. As a current research hotspot, the full waveform inversion (FWI) has been proven to be a promising technique for high-precision imaging of substructures, and has been applied in related practical engineering fields. However, most previous studies have focused on single-parameter (S-wave velocity) or double-parameter (S-wave and P-wave velocities) inversion. So, a complete PSV/Rayleigh-wave multi-parameter (S-wave and P-wave velocities and density) FWI method is developed in this paper to achieve accurate detection of underground utility tunnels. In this approach, the multi-parameter of the model are updated simultaneously during the inversion process to alleviate the negative influence on the S-wave velocity inversion accuracy due to the far deviation of the other two parameters from their true values. We tested the performance of the approach with a synthetic test and a real experiment. In the synthetic test, this method well characterized the position, shape and size of the embedded tunnel in the model, proving its effectiveness. Subsequently, the approach was applied to a field case investigated in Changsha city, China, and the inversion images revealed a tunnel with a burial depth of 4.5 m, height and width of 2 m and 4 m, respectively, which was identified as the detection target. The available borehole data verified the conclusion. The above results demonstrate the validity and time-effectiveness of the approach. It is expected to provide a reference for practical engineering applications at the same scale. • Detect utility tunnels using 2D PSV/Rayleigh-wave full waveform inversion. • Illustrated the validity of the method via a synthetic test and a field case. • Provide a complete workflow for handling field data. • Verify the reliability of the results by the borehole data. [ABSTRACT FROM AUTHOR]

Inverting Rayleigh-wave dispersion data may provide reliable velocity structure. A lot of linearized inversion methods are developed to handle this problem, however, which may be trapped by local extrema (minima or maxima) or no convergence of the solution without propriate initial models. Although several nonlinear approaches are also proposed, most of which face amount of computational consumption. In order to keep the balance, we introduce the homotopy method (HM), which can transform the nonlinear Rayleigh-wave dispersion equation into a linear equation system, and has global optimized property and less computational burden. We apply the HM to synthetic dispersion datasets, including noise-free and contaminated data. Through the comparison with the Competitive Particle Swarm Optimization (CPSO), a nonlinear approach, the HM is also less dependent on the initial model and may have higher computational efficiency. Real datasets from ambient noise in Weiyuan, Sichuan province, China, are further employed to study the effectiveness and applicability of the HM. Similar structure of more sufficient abnormal magnitude and boundary consistence is derived, which shows the uplift of the Weiyuan anticline with most less Root Mean Square Error (RMSE). It is concluded that, the HM is a potential candidate for most geophysical inversion problems with global optimization and efficiency balance. • The homotopy method (HM) for Rayleigh-wave dispersion inversion has been constructed. • The HM may obtain global optimized results in acceptable computational consumption. • The HM may refine the velocity structure for other linear inversion strategies. [ABSTRACT FROM AUTHOR]

Understanding the tectonic evolution of the North China Craton and its destruction mechanism requires the knowledge of eastern North China's fine crustal velocity structure. Using the two-year record of 342 ChinArray stations deployed in eastern North China, we obtain the Rayleigh wave phase velocity via ambient noise interferometry and Rayleigh wave ellipticity from ∼1000 teleseismic events. High-resolution sedimentary thickness and crustal 3D S-wave velocity structure are obtained by jointly inverting these observations. The results show that the Bohai Bay Basin is infilled with thick sediments and the Central Bohai Sea is the current depocenter with sedimentary thickness up to about 6 km. The crust and uppermost mantle beneath the Bohai Bay Basin are characterized by low velocity, indicating a high internal temperature of the crust. An upwelling of mantle thermal material under the crust of the Bohai Bay Basin continuously modifies the crust, suggesting that bottom-up thermochemical erosion is likely the primary control factor of crustal modification and thinning in this area. The uplift areas around the basin generally exhibit high velocity with weaker crustal modification, showing the heterogeneity of craton modification. Moreover, localized low-velocity zones observed beneath the Chifeng Volcanos, Dalainor Volcanos, and Kuandian Volcanos indicate the residual magmatism beneath these Quaternary volcanos. Furthermore, the magmatism beneath the Chifeng and Dalainor Volcanos shares a common magmatic source. • High-resolution 3-D S wave velocity model from joint inversion of Rayleigh wave phase velocity and ellipticity. • Bottom-up thermochemical erosion is the main control factor of crustal modification and thinning in Bohai Bay Basin. • Residual magmatism beneath the Chifeng Volcanos, Dalainor Volcanos and Kuandian Volcanos is observed. [ABSTRACT FROM AUTHOR]

Deep reflection seismic data contain abundant surface wave information for which the velocity structure in the near-surface shallow underground can be obtained using multichannel analysis of surface waves (MASW). This paper uses the MASW method to process deep reflection data in the Yuanmou area in Yunnan province, China. The MASW method uses the phase velocity spectral transformation of Rayleigh waves to obtain its dispersion curve. The initial model for different lithology classifications is established to invert the underground velocity structure. This study obtains a two-dimensional shear wave velocity structure profile to investigate the shear wave velocity structure. Generally, the study results have shown that the shear wave velocity structure obtained by the MASW method corresponds well with the surface conditions and accurately reflects faults' changes, folds, and lithology. Moreover, the formation sand content calculation shows a large difference in Dongshan sag's formation sand content. The sand contents of Cretaceous and Middle Jurassic strata are over 30% similar, and the sandstone content of underlying Early Jurassic strata is mostly 30% lower. The stratum buried depth of Early Jurassic strata is between 0– 800 m. The dip angle of LZJF at this location is 90°. The west side of the LZJF is based on Proterozoic uplift, and the Quaternary sedimentary thickness exceeds 300 m above the uplift stratum. Whereas on the east side of the LZJF, the stratum of the Dongshan sag section is mainly a synclinal structure. • Multichannel analysis of surface waves method is applicable to surface wave data in deep reflection profile. • The interlayer velocity difference method can be used to distinguish strata by shear wave velocity. • Shallow velocity structure can distinguish shallow geological structure with high resolution. [ABSTRACT FROM AUTHOR]

We present the current status of seismic noise interferometry to reconstruct the seismic velocity and discuss the four phases from single-station data preparation to quality control of data processing procedures. Each phase of the processing procedure has been discussed in detail with salient examples using seismic data acquired in Changbaishan volcano region. In the end, we use continuous recordings in Jilin, China to track the temporal change of the seismic velocity variations with the method promoted in this paper. We filter the data between the frequency band 0.02 and 0.1 Hz, which the Rayleigh waves are most sensitive to the shear wave velocities in the crust and uppermost mantle. The long-term seismic variations present strong seasonal influence which may be caused by precipitation. We find clear evidence that the seismic velocity drops by up to ∼0.8% which may be caused by the dilatation of the volcanic edifice before the Mar. 11 2011 Japan earthquake. [ABSTRACT FROM AUTHOR]

Rayleigh waves significantly compromise the safety of tunnel portals. This paper establishes a three-dimensional numerical model, with a plastic-damage model for the concrete lining structure, to analyze the damage evolution of the tunnel portal during the longitudinal propagation of Rayleigh waves. To generate the wave field, a Rayleigh wave input method based on viscous-spring artificial boundary is developed. The submodeling technique is employed to overcome difficulties introduced by contradictions between element size, model scale and affordable computational cost. The simulation results, including the deformation of pavement at the entrance and the crack pattern of the tunnel lining, correspond well with the field observation of the Longxi Tunnel during the Wenchuan Earthquake. This paper proposes that the opening width of predominant circumferential cracks and a dimensionless damage index based on the internal damage variable can be used to quantitatively estimate the damage extent of the lining structure. The result of damage assessment shows that all damage is limited within a certain scope of the tunnel portal and that the extent of each crack decreases with its increasing distance from the entrance. The extent of damage may also be induced through earthquake loading with a relatively lower amplitude. Therefore, the cyclic and accumulative effect of successive earthquake loading over time, rather than simply, the effect of loading with a maximum amplitude, can determine the final damage state of lining structure. Although incapable of preventing the appearance of hairline cracks, the strengthening effect of reinforcement remarkably reduces the maximum width of crack openings and the overall damage extent of the lining structure. Moreover, the presence of reinforcing steels prevents micro-cracks from expanding to wider crack, which is essential to keep the tunnel lining waterproof and mechanically stabilized. The simulation methodology introduced in this paper could also potentially reliably predict the damage process of the tunnel lining and the extent of damage under the effect of complicated earthquake loading, aside from the Rayleigh wave. [ABSTRACT FROM AUTHOR]

High precision detection of the shallow-surface structure is of great significance to geotechnical engineering and archaeological geophysical research. Surface wave Full waveform inversion (FWI) is attracting more and more attention in shallow seismic exploration. The FWI of Love waves is more straightforward and has a higher precision and resolution compared with Rayleigh waves. In the classic gradient-based FWI algorithm, the gradient amplitude does not scale with increasing depth due to the coupling effect and double scattering; thus, the inversion image cannot represent the significant small-scale characteristic structures in archaeogeophysics. To overcome the above limitations, a pre-conditioned FWI approach was presented, and a complete elastic Love waves FWI workflow was developed for archaeogeophysics. The superior performance of the developed method was verified through synthesis tests and a field experiment. The synthetic tests on a tomb model show that the pre-conditioned approach has a better parameter reconstruction capability, can characterize small-scale anomalies, improves the convergence rate, and has a strong anti-noise ability. In the field experiment, the pre-conditioned approach-based Love waves FWI workflow was adopted to invert the recorded Love waves datasets gathered in Xianyang City, China. The target of the survey was to determine the location and approximate size of a buried ancient tomb to provide reliable guidance for further excavation. The obtained FWI image revealed an underground profile with a depth of 9.5 m, and a low-velocity anomaly with a height of about 1.6 m and a length of about 4.7 m was delineated, which we identified as the tomb. The subsequent excavation confirmed this conclusion. The above results show that the complete Love wave FWI workflow developed has the ability to perform accurate imaging under the condition of few shots. • Focus on characterizing high-precision small-scale structures for archaeogeophysics. • Develope a complete workflow of pre-conditioned approach-based 2D Love waves FWI. • Demonstrate the superior performance of our method through synthesis and field tests. • Reveal the structure of an ancient tomb accurately by inverting field data. [ABSTRACT FROM AUTHOR]

We present a three-dimensional model of shear wave velocity for the upper mantle of China and the surrounding region by analyzing 50,338 vertical component multi-mode Rayleigh wave seismograms, recorded at 144 permanent and more than 300 temporary broadband stations in and around China. The procedure involves combination of 1-D path average models obtained by modeling each Rayleigh waveform up to the 4th higher mode in a tomographic inversion scheme. The dense station network and the use of multi-mode analysis help to achieve a lateral resolution of a few hundred kilometers down to 400 km depth. The seismic lithosphere, as it is defined by the crust and the high velocity mantle lid, is to the first order thin in east China and thick in the west, with a high velocity lid extending down to about 200 km depth beneath much of the Tibet–Pamir plateau. Beneath India, the thickness of the seismic lithosphere gradually increases from ~ 100 km in south India to more than 150 km in north India, where it underthrusts the Tibetan plateau to approximately the Jinsha River Suture. High velocity lid extending down to 100–150 km depth is also observed in the Tarim basin, Sichuan basin and Ordos block. In the eastern part of the North China craton the seismic lithosphere is probably close to or thinner than 70 km. Adjacent to these areas, the high velocity lid in the eastern Yangtze craton and South China fold system extends down to 70–80 km depth. A large-scale subhorizontal high velocity body is observed at depths of 150–350 km beneath the entire east China cratonic areas. This high velocity body might be the remnant of a delamination process which resulted in the decratonization of the North China and the Yangtze cratons. [ABSTRACT FROM AUTHOR]

Highlights: [•] 3-D S-wave structure (10–100km) beneath the North China is constructed. [•] The S-wave velocities in different sides of the NSGL are distinctly different. [•] Upwelling asthenosphere beneath Datong may contribute the destruction of the NCC. [•] The ZPFZ may act as the channel of upwelling asthenosphere. [•] The low-V zone in the BTT region may due to the upwelling asthenosphere. [ABSTRACT FROM AUTHOR]

SUMMARY We imaged the crust and uppermost mantle structure beneath northeastern (NE) China with fundamental mode Rayleigh waves recorded by 125 broad-band stations deployed in the region. Rayleigh wave phase and group velocities along more than 700 interstation paths were estimated using the wavelet transformation method and then these data were utilized to construct 2-D phase and group velocity maps in the period range of 15-60 s. Owing to the dense ray coverage and short ray path, our results provide better lateral resolution in the NE China region compared with previous phase and group velocity studies. The regularized Rayleigh wave phase and group velocity dispersions at each cell were jointly inverted to determine 1-D shear wave velocity structure using the linear inversion method and then assembled into a 3-D model. Our results show that obvious low velocities exist in the uppermost mantle beneath the Changbaishan volcanic region, which may be due to asthenospheric upwelling. The thin lithosphere with fast S-wave velocity in the lower crust of the Songliao Basin implies that the lithospheric mantle beneath NE China is partly removed. [ABSTRACT FROM AUTHOR]

SUMMARY Two years of continuous recordings of ambient seismic noise observed at 354 stations in South China from 2009 to 2010 are used to estimate Rayleigh wave group and phase velocity maps from 6 to 40 s period. These results are merged with Rayleigh wave phase velocity maps from 25 to 70 s period derived from earthquakes in the same time frame. Eikonal tomography generates the dispersion maps, which, by Monte-Carlo inversion, are used to estimate a 3-D Vsv model of the crust and upper mantle down to a depth of 150 km across all of South China with attendant uncertainties. A clear image emerges of the 'West Yangtze Block', a region of the western Yangtze Craton characterized by relatively thick crust (∼40 km) overlying a seismic mantle lithosphere that extends to at least 150 km that may have been the nucleus for the formation of the Yangtze craton in the Archean and may present a present-day obstacle to the eastward expansion of Tibet. The West Yangtze Block contrasts with the thinner crust (∼30 km) and mantle lithosphere (∼70-80 km) beneath the eastern Yangtze Craton and South China Foldbelt. These observed differences are consistent with processes associated with flat slab subduction in the Mesozoic that may have eroded the lithosphere of the eastern Yangtze Craton and the South China Foldbelt. [ABSTRACT FROM AUTHOR]