Long-period free oscillations provide robust information for the spatio-temporal characteristics of large earthquakes.In this study,we employ a normal-mode summation algorithm to generate threecomponent seismograms wi...Long-period free oscillations provide robust information for the spatio-temporal characteristics of large earthquakes.In this study,we employ a normal-mode summation algorithm to generate threecomponent seismograms within an aspherical,anelastic,and rotating Earth model,focusing on the excitation of seismic normal modes by the 2011 Tohoku megathrust earthquake.Specifically,we analyze the effects of seismic source parameters,including fault geometry,focal depth,and rupture duration.By comparing synthetic free oscillation spectra with observed data,we validate several source mechanisms and emphasize the need for horizontal observations to improve seismic mechanism inversions.Our quantitative analyses reveal that among fault geometry parameters,dip and slip angles have a more pronounced impact on excitation amplitudes than fault strikes.Certain fault configurations enhance the detectability of specific modes,underscoring the relationship between fault geometry and mode excitation.Normal modes also exhibit varying sensitivity to focal depth,with significant excitation amplitude changes at discontinuity boundaries.Additionally,we demonstrate that while rupture duration can be inferred by minimizing differences between observed and synthetic spectra,more extensive records and modes should be included.展开更多
The Chilean Pampean flat slab subduction segment is characterized by the nearly horizontal subduction of the Nazca Plate within the depth range of 100-120 km.Numerous seismic tomography studies have been conducted to ...The Chilean Pampean flat slab subduction segment is characterized by the nearly horizontal subduction of the Nazca Plate within the depth range of 100-120 km.Numerous seismic tomography studies have been conducted to investigate its velocity structure;however,they have used only seismic body wave data or surface wave data.As a result,the existing velocity models in the region may have relatively large uncertainties.In this study,we use body wave arrival times from earthquakes occurring in central Chile between 2014 and 2019,as well as Rayleigh wave phase velocity maps at periods of 5-80 s from ambient noise empirical Green’s functions in Chile.By jointly using body wave arrival times and surface wave dispersion data,we refine the VS model and improve earthquake locations in the central Chile subduction zone.Compared with previous velocity models,our velocity model better reveals an eastward-dipping high-velocity plate representing the subducting Nazca Plate,which is 40-50 km thick and is more consistent with the slab thickness estimated by receiver function imaging and thermal modeling.Overall,the intraslab seismicity distribution spatially correlates well with the slab high-velocity anomalies except along the subduction paths of the CopiapóRidge and Juan Fernández Ridge.Additionally,parallel low-velocity stripes are imaged beneath the subducting plate,which are likely associated with the accumulated melts.The joint inversion velocity model also resolves widespread low-velocity anomalies in the crust beneath the Central Volcanic Zone of the central Andes,likely representing crustal magma chambers for various volcanoes.展开更多
The Yuncheng Basin,located in the southern part of the Fenwei Rift,North China,exhibits obvious crust thinning(Moho uplift of 6-8 km)and shallow Curie point depth(less than 18 km)and hence holds great potential for ge...The Yuncheng Basin,located in the southern part of the Fenwei Rift,North China,exhibits obvious crust thinning(Moho uplift of 6-8 km)and shallow Curie point depth(less than 18 km)and hence holds great potential for geothermal resources.However,geothermal exploration within the Yuncheng Basin typically faces significant challenges due to civil and industrial noise from dense populations and industrial activities.To address these challenges,both Controlled-Source Audio-frequency Magnetotellurics(CSAMT)and radon measurements were employed in Baozigou village to investigate the geothermal structures and identify potential geothermal targets.The CSAMT method effectively delineated the structure of the subsurface hydrothermal system,identifying the reservoir as Paleogene sandstones and Ordovician and Cambrian limestones at elevations ranging from−800 m to−2500 m.In particular,two concealed normal faults(F_(a)and F_(b))were newly revealed by the combination of CSAMT and radon profiling;these previously undetected faults,which exhibit different scales and opposing dips,are likely to be responsible for controlling the convection of thermal water within the Basin’s subsurface hydrothermal system.Moreover,this study developed a preliminary conceptual geothermal model for the Fen River Depression within the Yuncheng Basin,which encompasses geothermal heat sources,cap rocks,reservoirs,and fluid pathways,providing valuable insights for future geothermal exploration.In conjunction with the 3D geological model constructed from CSAMT resistivity structures beneath Baozigou village,test drilling is recommended in the northwestern region of the Baozigou area to intersect the potentially deep fractured carbonates that may contain temperature-elevated geothermal water.This study establishes a good set of guidelines for future geothermal exploration in this region,indicating that high-permeability faults in the central segments of the Fen River Depression are promising targets.展开更多
The Mohorovicic discontinuity(Moho)boundary separating the Earth’s crust and mantle reflects the evolutionary trajectory of the Earth’s crust,yielding crucial insights into crustal formation,tectonic evolution,and p...The Mohorovicic discontinuity(Moho)boundary separating the Earth’s crust and mantle reflects the evolutionary trajectory of the Earth’s crust,yielding crucial insights into crustal formation,tectonic evolution,and profound dynamic processes.However,the prevailing Moho models for China and its adjacent areas suffer from limited accuracy,owing to the irregular and sparse distribution of seismic data collection.In this study,we employ gravimetric data to derive Moho depth,and employ Bott’s regularization method,integrating gravity and seismic data to reconstruct the Moho structure with high precision in a three-dimensional framework across China and its adjacent areas.By optimizing gravity potential field separation and interface inversion techniques,we present a detailed and accurate zoning scheme for classifying China and its adjacent areas into 35 gradient belts,6 primary tectonic units,and 35 secondary tectonic units,based on the spatial distribution characteristics of the Moho discontinuity.Notably,our tectonic pattern division results surpass previous studies in terms of resolution,providing a wealth of tectonic information.Leveraging the Moho depth model of China and its adjacent areas,we discuss orogenic belts,sedimentary basins,fault systems,plate boundaries,and land-sea coupled tectonic patterns.We meticulously summarize the Moho depth distribution characteristics of each tectonic unit,while exploring the macrostructural framework and geological significance of the study area.Our findings highlight the close relationship between China and its adjacent areas Moho depth model and deep geodynamics,elucidating the tectonic evolution both between and within tectonic plates,as well as the tectonic effects induced by mantle dynamics.These insights have crucial implications for the study of deep geodynamics in China and its adjacent areas.展开更多
Distributed acoustic sensing(DAS)has rapidly emerged as a transformative technology in seismic exploration,particularly in vertical seismic profiles(vsP).However,the acquired vsP data suffer from strong coherent DAs c...Distributed acoustic sensing(DAS)has rapidly emerged as a transformative technology in seismic exploration,particularly in vertical seismic profiles(vsP).However,the acquired vsP data suffer from strong coherent DAs coupling noise and random noise.Current deep learning denoising methods,dependent on noise labels derived from conventional denoising techniques,fall short in addressing the unique noise properties inherent in DAS data.To address this challenge,we propose an exponential decay curve-constrained empirical mode decomposition(EDcc-EMD)analysis-based supervised denoising network.Our method begins with extracting the initial noise from the field DAs vsP data through the traditional EMD method.Despite containing some signal leakage,this noise is further processed through EMD to derive intrinsic mode functions(IMFs).We,then,analyze the correlation coefficients between these IMFs and the initial noise,applying an exponential decay curve(EDC)law to isolate pure noise.This refined noise data serves as accurate labels,enhancing the denoising network's precision.Meanwhile,most of the methods usually consider the t-x domain features and ignore the important frequency-domain features.Consequently,we train our network with frequency-domain data instead of time domain data,capitalizing on the more distinct separation of noise and signal characteristics,thereby facilitating more effective noise-signal discrimination.The experimental results demonstrate that our method significantly enhances the denoising performance and successfully recovers weak signals.展开更多
The Tanlu Fault Zone(TLFZ),recognized as the largest active strike-slip fault system in eastern China,exhibits distinct structural features and seismic activities across its various segments.To elucidate the structura...The Tanlu Fault Zone(TLFZ),recognized as the largest active strike-slip fault system in eastern China,exhibits distinct structural features and seismic activities across its various segments.To elucidate the structural characteristics of the upper and middle crust in the Zhangbaling Uplift(ZBU)segment of the TLFZ,we employed ambient noise data collected from a dense seismic array comprising 192 nodes,deployed in 2020.Utilizing ambient noise tomography,we derived a three-dimensional S-wave velocity(Vs)structure of the region,extending to a depth of 10 km.The tomographic results reveal a prominent low-velocity anomaly at depths of 0–2 km along the fault zone,which correlates with the fault graben structure.According to the Vscharacteristics,the Mingguang Graben in the northern part of Zhangbaling extends to a depth of 3 km,whereas on the eastern flank of the Hefei Basin in the south,it reaches 1.5 km.Additionally,several NW-trending low-velocity stripes are identified at depths of 3–5 km on the eastern side of the Bengbu Uplift and the Hefei Basin,likely corresponding to NW-trending left-lateral hidden faults.By integrating the regional velocity structure,surface GPS directions,and earthquake focal mechanisms,we proposed a tectonic model for the Zhangbaling segment of the TLFZ.This model suggests that the NWtrending hidden faults may play a crucial role in modulating the near east-west stress loading on the TLFZ.展开更多
The mantle plume model describes a crucial form of upward(bottom to top)movement of materials and energy within the Earth's interior.Together with the downward(top to bottom)movement of subducting slabs,it collect...The mantle plume model describes a crucial form of upward(bottom to top)movement of materials and energy within the Earth's interior.Together with the downward(top to bottom)movement of subducting slabs,it collectively forms the primary upward and downward channels for the transport of materials and energy between the Earth's surface and the deep mantle,leading to intense volcanic activities and climatic-environmental effects on the surface.The establishment and refinement of the mantle plume model have undergone a relatively long process,during which a series of significant papers have been produced.We have selected six typically representative papers from these works for interpretation,aiming to present to readers the key records of the mantle plume model,including its establishment,verification,and associated effects.These papers cover the following aspects:the proposal of the mantle plume model,the establishment of the“head-tail”morphology of mantle plumes,the constraints of geochemical observations on the chemical composition of mantle plumes,the constraints of seismological observations on the morphological structure of mantle plumes,the surface manifestations of mantle plumes,and the impacts of mantle plumes on the Earth's surface environment.From different perspectives,these papers form the cornerstones in the development of the mantle plume model,provide key supporting nodes for this theoretical framework,and offer important insights and references for subsequent research.展开更多
Transform faults represent one of the three primary types of plate boundaries in plate tectonics theory and constitute an essential component of this framework.In general,they are classified into oceanic and continent...Transform faults represent one of the three primary types of plate boundaries in plate tectonics theory and constitute an essential component of this framework.In general,they are classified into oceanic and continental transform faults based on the nature of their separated plates.Owing to significant differences in properties between continental and oceanic lithospheres,continental transform faults exhibit more complex structures than their oceanic counterparts.Continental transform faults are strike-slip boundaries where stress and strain are highly concentrated.They typically extend for hundreds to thousands of kilometers and have experienced tens to hundreds of kilometers of strike-slip displacement.These faults may appear as a single master fault or as complex fault systems with multiple branches.Their deep structures and deformation patterns at varying depths offer critical insights into the structure and rheological behavior of the continental lithosphere.Imaging fine-scale structures of continental transform faults via geophysical methods is crucial for understanding their nature and evolution.Seismic anisotropy results provide key constraints on their deep deformation characteristics.This paper reviews geophysical studies from typical continental transform fault regions and investigates their deep structure and deformation mechanisms by integrating geological and geodetic observations.Although these fault systems are structurally diverse,several common features emerge.(1)Nearly all continental transform faults cut through the entire crust and extend into the upper mantle,with significant seismic anisotropy observed within the fault zones.(2)Regardless of whether the fault is a single narrow structure or a branching system,uppercrustal segments typically form narrow zones of strain concentration where brittle friction accommodates slip and seismicity is concentrated.The shear zone broadens with depth,reaching tens of kilometers in width within the lithospheric mantle.(3)The width of a continental transform fault correlates with the nature of the lithosphere it cross-cuts.Narrow shear zones form in rigid and ancient lithosphere,otherwise,broader distributed deformation occurs.(4)Non-strike-slip components(compression or tension)significantly influence fault zone complexity.Recent ocean drilling programs have advanced understanding of oceanic transform faults,yet knowledge of continental transform fault structure and evolution remains limited.Advances in seismic imaging and observational techniques will enable higher-resolution characterization of these faults,providing new constraints on their seismic behavior and earthquake migration patterns.展开更多
The discrimination test of ambiguity resolution,also known as ambiguity validation,is a vital procedure to quantify the reliability of Global Navigation Satellite System(GNSS)ambiguity-fixed solutions.Several well-kno...The discrimination test of ambiguity resolution,also known as ambiguity validation,is a vital procedure to quantify the reliability of Global Navigation Satellite System(GNSS)ambiguity-fixed solutions.Several well-known tests,including the R-ratio,W-ratio,and Ambiguity Dilution of Precision,usually employ empirical thresholds for the discrimination of integer candidates.We aim at improving the reliability of ambiguity validation by integrating these tests using a machine learning model called the Support Vector Model(SVM).The dataset used consists of simulated real-time Precise Point Positioning Ambiguity Resolution(PPP-AR)solutions in 1-day batch.Specifically,the training dataset is derived using the observations from days 1-31 of year 2023,while the testing dataset is generated using the observations from days 153-159 of years 2022 and 2024.The results reveal that the SVM validates PPP-AR at a success rate of 83%for the independent testing dataset.At the same time,the mean error of the convergence time predicted by the SVM is about 1.0 min,whereas that by the R-ratio test up to 5.0 min.A vehicle-borne experiment conducted on day 362 of year 2020 further demonstrates the improvement of this method in a kinematic scenario,with a success rate of 92%compared to 82%with the conventional R-ratio test.展开更多
Surface wave tomography based on dispersion is an important approach for imaging the velocity structure of the Earth's crust and upper mantle.Traditional surface wave tomography methods based on dispersion data ty...Surface wave tomography based on dispersion is an important approach for imaging the velocity structure of the Earth's crust and upper mantle.Traditional surface wave tomography methods based on dispersion data typically involve a multistep process:initial construction of 2D phase/group velocity maps,a point-wise inversion of dispersion data to derive 1D profiles of shear wave velocity as a function of depth at each grid point,and final construction of the 3D velocity model.However,conventional 2D tomography methods have certain limitations.For instance,linearized inversion methods are highly sensitive to the choice of the initial velocity model and regularization parameters,while eikonal tomography method requires dense observations.Here,we propose a surface wave tomography method based on physics-informed neural networks,which can construct the phase/group velocity maps of multiple measurement periods simultaneously,eliminating the need for repeated individual inversions for each period.The network comprises two branches,one taking in the coordinates of the virtual source and station as well as period as input to fit the observed surface wave travel times,and another one taking in the station coordinates and period to predict the phase/group velocity.The two branches are constrained by the eikonal equation.After the training is completed,the velocity of each grid point in each period can be queried using the neural network and form the phase/group velocity maps.We test the new method using data from the Feidong and the Weifang dense seismic arrays deployed around the Tanlu Fault Zone in eastern China,and compare the tomography results with those of the traditional method.We demonstrate that the new method is a meshless tomography approach with data adaptive resolution.In addition,it does not require an initial velocity model or explicit regularizations.This method is highly automated,simple,and user-friendly,and it has great potential for integration with existing automatic dispersion curve extraction techniques to achieve automated surface wave tomography without human intervention.展开更多
Radial anisotropy structures are essential for understanding tectonic stress fields and distinguishing between lowvelocity zones(LVZs)associated with sedimentary basins and fault damage zones,offering critical insight...Radial anisotropy structures are essential for understanding tectonic stress fields and distinguishing between lowvelocity zones(LVZs)associated with sedimentary basins and fault damage zones,offering critical insights for comprehensive seismic hazard assessments.This study employed ambient noise tomography to investigate the fault zone and surrounding structures of the Chenghai Fault in the Binchuan Basin,Yunnan Province,China.Utilizing three-component waveform data collected from a linear dense seismic array consisting of 114 stations,we constructed a high-resolution shear wave velocity and radial anisotropy model.Our results reveal notable variations in radial anisotropy across the study region,with pronounced negative radial anisotropy surrounding the Chenghai Fault,likely reflecting fault damage.In contrast,positive radial anisotropy is observed beneath the Dongshan Mountain,indicative of extensional stress.The LVZ beneath the Binchuan Basin exhibits positive radial anisotropy,suggesting that this LVZ is primarily due to sedimentary deposits.Based on the shear wave velocity and radial anisotropy structure,we infer that the Chenghai Fault,influenced by east-west extensional tectonics,behaves as a high-angle normal fault.Additionally,another fault with a relatively lower dip angle is identified within the Binchuan Basin.The tectonic activity of the Chenghai Fault played a significant role in the initiation of sedimentation within the Binchuan Basin during the Neogene period.These findings are crucial for advancing the understanding of fault dynamics and provide essential insights for refining seismic hazard assessments in the region.展开更多
The Sichuan-Yunnan region hosts numerous large active faults with complex spatial distributions and intricate intersections,where moderate-to-strong earthquakes occur frequently.Obtaining source mechanism solutions fo...The Sichuan-Yunnan region hosts numerous large active faults with complex spatial distributions and intricate intersections,where moderate-to-strong earthquakes occur frequently.Obtaining source mechanism solutions for these earthquakes is not only essential for analyzing the regional crustal stress regime,fault geometries,activity behaviors and seismic potentials,but also is critical for assessing seismic hazards.Previous studies have obtained source mechanism catalogs of regional historical moderate-to-strong earthquakes based on 1D crustal velocity models,or inverted source mechanisms for few representative events based on 3D velocity models incorporating lateral variations.However,a systematic source mechanism inversion framework,which integrates regional high-resolution 3D velocity models with significant topographic relief,still remains absent for the Sichuan-Yunnan region.Using the high-resolution 3D velocity model SWChinaCVM-2.0 with regional topographic relief,we first construct a comprehensive strain Green's tensor library for the 181 permanent broadband seismic stations across the Sichuan-Yunnan region.In particular,the forward modeling employs the spectral element method(SEM)with source-receiver reciprocity,followed by highly efficient compression of the computed library.Subsequently,a systematic source mechanism inversion is conducted for the 563 M_(L)≥4 earthquakes occurring in the region during 2009-2021 using full waveform matching.With the derived solutions of fault planes,full moment tensors and moment magnitudes,a new-generation,accurate source mechanism catalog for moderate-to-strong earthquakes in the Sichuan-Yunnan region is obtained.This catalog can provide essential data for future geoscience studies in the Sichuan-Yunnan region,and is a foundational geophysical work driven by new techniques and methods.In the future,the inversion framework can also be applied to areas with high seismic risks such as North China and Xinjiang,providing essential supports for rapid and accurate determination of source parameters and assessment of seismic hazards.展开更多
基金supported by the National Natural ScienceFoundation of China(42204003,42274011,42388102,42192533,42192531)the Natural Science Foundation of Wuhan(2024040701010027)+1 种基金the Open Fund Supported by the State KeyLaboratory of Precision Geodesy,Innovation Academy for PrecisionMeasurement Science and Technology,Chinese Academy of Sci-ences(SKLGED2024-1-1)the Open Fund Supported by KeyLaboratory of Polar Environment Monitoring and Public Gover-nance(Wuhan University),Ministry of Education(202401)。
文摘Long-period free oscillations provide robust information for the spatio-temporal characteristics of large earthquakes.In this study,we employ a normal-mode summation algorithm to generate threecomponent seismograms within an aspherical,anelastic,and rotating Earth model,focusing on the excitation of seismic normal modes by the 2011 Tohoku megathrust earthquake.Specifically,we analyze the effects of seismic source parameters,including fault geometry,focal depth,and rupture duration.By comparing synthetic free oscillation spectra with observed data,we validate several source mechanisms and emphasize the need for horizontal observations to improve seismic mechanism inversions.Our quantitative analyses reveal that among fault geometry parameters,dip and slip angles have a more pronounced impact on excitation amplitudes than fault strikes.Certain fault configurations enhance the detectability of specific modes,underscoring the relationship between fault geometry and mode excitation.Normal modes also exhibit varying sensitivity to focal depth,with significant excitation amplitude changes at discontinuity boundaries.Additionally,we demonstrate that while rupture duration can be inferred by minimizing differences between observed and synthetic spectra,more extensive records and modes should be included.
基金funded by the National Natural Science Foundation of China under Grant 42230101the National Agency for Research and Development of Chile(ANID)by Projects AFB180004 and AFB220002the ANID Programa de Cooperación Internacional(PCI)Grant PII-180003.
文摘The Chilean Pampean flat slab subduction segment is characterized by the nearly horizontal subduction of the Nazca Plate within the depth range of 100-120 km.Numerous seismic tomography studies have been conducted to investigate its velocity structure;however,they have used only seismic body wave data or surface wave data.As a result,the existing velocity models in the region may have relatively large uncertainties.In this study,we use body wave arrival times from earthquakes occurring in central Chile between 2014 and 2019,as well as Rayleigh wave phase velocity maps at periods of 5-80 s from ambient noise empirical Green’s functions in Chile.By jointly using body wave arrival times and surface wave dispersion data,we refine the VS model and improve earthquake locations in the central Chile subduction zone.Compared with previous velocity models,our velocity model better reveals an eastward-dipping high-velocity plate representing the subducting Nazca Plate,which is 40-50 km thick and is more consistent with the slab thickness estimated by receiver function imaging and thermal modeling.Overall,the intraslab seismicity distribution spatially correlates well with the slab high-velocity anomalies except along the subduction paths of the CopiapóRidge and Juan Fernández Ridge.Additionally,parallel low-velocity stripes are imaged beneath the subducting plate,which are likely associated with the accumulated melts.The joint inversion velocity model also resolves widespread low-velocity anomalies in the crust beneath the Central Volcanic Zone of the central Andes,likely representing crustal magma chambers for various volcanoes.
基金supported by the Shanxi Province Basic Research Program(No.20210302123374)Yuncheng University Doctoral Research Initiation Fund(No.YQ-2021008)+3 种基金Excellent doctors come to Shanxi to reward scientific research projects(No.QZX-2023020)Open Fund of State Key Laboratory of Precision Geodesy(No.SKLPG2025-1-1)Joint Open Fund of the Research Platforms of School of Computer Science,China University of Geosciences,Wuhan(No.PTLH2024-B-03)Hubei Provincial Natural Science Foundation Project(No.2025AFC095).
文摘The Yuncheng Basin,located in the southern part of the Fenwei Rift,North China,exhibits obvious crust thinning(Moho uplift of 6-8 km)and shallow Curie point depth(less than 18 km)and hence holds great potential for geothermal resources.However,geothermal exploration within the Yuncheng Basin typically faces significant challenges due to civil and industrial noise from dense populations and industrial activities.To address these challenges,both Controlled-Source Audio-frequency Magnetotellurics(CSAMT)and radon measurements were employed in Baozigou village to investigate the geothermal structures and identify potential geothermal targets.The CSAMT method effectively delineated the structure of the subsurface hydrothermal system,identifying the reservoir as Paleogene sandstones and Ordovician and Cambrian limestones at elevations ranging from−800 m to−2500 m.In particular,two concealed normal faults(F_(a)and F_(b))were newly revealed by the combination of CSAMT and radon profiling;these previously undetected faults,which exhibit different scales and opposing dips,are likely to be responsible for controlling the convection of thermal water within the Basin’s subsurface hydrothermal system.Moreover,this study developed a preliminary conceptual geothermal model for the Fen River Depression within the Yuncheng Basin,which encompasses geothermal heat sources,cap rocks,reservoirs,and fluid pathways,providing valuable insights for future geothermal exploration.In conjunction with the 3D geological model constructed from CSAMT resistivity structures beneath Baozigou village,test drilling is recommended in the northwestern region of the Baozigou area to intersect the potentially deep fractured carbonates that may contain temperature-elevated geothermal water.This study establishes a good set of guidelines for future geothermal exploration in this region,indicating that high-permeability faults in the central segments of the Fen River Depression are promising targets.
基金supported by the National Natural Science Foundation of China(Grant Nos.42474121 and 42192535)the Basic Frontier Science Research Program of the Chinese Academy of Sciences(Grant No.ZDBS-LY-DQC028).
文摘The Mohorovicic discontinuity(Moho)boundary separating the Earth’s crust and mantle reflects the evolutionary trajectory of the Earth’s crust,yielding crucial insights into crustal formation,tectonic evolution,and profound dynamic processes.However,the prevailing Moho models for China and its adjacent areas suffer from limited accuracy,owing to the irregular and sparse distribution of seismic data collection.In this study,we employ gravimetric data to derive Moho depth,and employ Bott’s regularization method,integrating gravity and seismic data to reconstruct the Moho structure with high precision in a three-dimensional framework across China and its adjacent areas.By optimizing gravity potential field separation and interface inversion techniques,we present a detailed and accurate zoning scheme for classifying China and its adjacent areas into 35 gradient belts,6 primary tectonic units,and 35 secondary tectonic units,based on the spatial distribution characteristics of the Moho discontinuity.Notably,our tectonic pattern division results surpass previous studies in terms of resolution,providing a wealth of tectonic information.Leveraging the Moho depth model of China and its adjacent areas,we discuss orogenic belts,sedimentary basins,fault systems,plate boundaries,and land-sea coupled tectonic patterns.We meticulously summarize the Moho depth distribution characteristics of each tectonic unit,while exploring the macrostructural framework and geological significance of the study area.Our findings highlight the close relationship between China and its adjacent areas Moho depth model and deep geodynamics,elucidating the tectonic evolution both between and within tectonic plates,as well as the tectonic effects induced by mantle dynamics.These insights have crucial implications for the study of deep geodynamics in China and its adjacent areas.
基金supported by the National Natural Science Foundation of China(Nos.42404140,42130808)the National Key Research and Development Program of China under grant 2021YFA0716802.We thank Professor Xiang-Fang Zeng from Innovation Academy for Precision measurement Science and Technology,Chinese Academy of Sciences for his valuable discussions.
文摘Distributed acoustic sensing(DAS)has rapidly emerged as a transformative technology in seismic exploration,particularly in vertical seismic profiles(vsP).However,the acquired vsP data suffer from strong coherent DAs coupling noise and random noise.Current deep learning denoising methods,dependent on noise labels derived from conventional denoising techniques,fall short in addressing the unique noise properties inherent in DAS data.To address this challenge,we propose an exponential decay curve-constrained empirical mode decomposition(EDcc-EMD)analysis-based supervised denoising network.Our method begins with extracting the initial noise from the field DAs vsP data through the traditional EMD method.Despite containing some signal leakage,this noise is further processed through EMD to derive intrinsic mode functions(IMFs).We,then,analyze the correlation coefficients between these IMFs and the initial noise,applying an exponential decay curve(EDC)law to isolate pure noise.This refined noise data serves as accurate labels,enhancing the denoising network's precision.Meanwhile,most of the methods usually consider the t-x domain features and ignore the important frequency-domain features.Consequently,we train our network with frequency-domain data instead of time domain data,capitalizing on the more distinct separation of noise and signal characteristics,thereby facilitating more effective noise-signal discrimination.The experimental results demonstrate that our method significantly enhances the denoising performance and successfully recovers weak signals.
基金supported by the National Key R&D Program of China(Grant No.2022YFF0800701)the Joint Open Fund of Mengcheng National Geophysical Observatory(Grant No.MENGO-202002)+1 种基金the National Natural Science Foundation of China(Grant No.42104063)the Earthquake Spark Program Project of China Earthquake Administration(Grant No.XH24020B)。
文摘The Tanlu Fault Zone(TLFZ),recognized as the largest active strike-slip fault system in eastern China,exhibits distinct structural features and seismic activities across its various segments.To elucidate the structural characteristics of the upper and middle crust in the Zhangbaling Uplift(ZBU)segment of the TLFZ,we employed ambient noise data collected from a dense seismic array comprising 192 nodes,deployed in 2020.Utilizing ambient noise tomography,we derived a three-dimensional S-wave velocity(Vs)structure of the region,extending to a depth of 10 km.The tomographic results reveal a prominent low-velocity anomaly at depths of 0–2 km along the fault zone,which correlates with the fault graben structure.According to the Vscharacteristics,the Mingguang Graben in the northern part of Zhangbaling extends to a depth of 3 km,whereas on the eastern flank of the Hefei Basin in the south,it reaches 1.5 km.Additionally,several NW-trending low-velocity stripes are identified at depths of 3–5 km on the eastern side of the Bengbu Uplift and the Hefei Basin,likely corresponding to NW-trending left-lateral hidden faults.By integrating the regional velocity structure,surface GPS directions,and earthquake focal mechanisms,we proposed a tectonic model for the Zhangbaling segment of the TLFZ.This model suggests that the NWtrending hidden faults may play a crucial role in modulating the near east-west stress loading on the TLFZ.
基金funded by the National Natural Science Foundation of China(Grant Nos.42241117 and 42425402)。
文摘The mantle plume model describes a crucial form of upward(bottom to top)movement of materials and energy within the Earth's interior.Together with the downward(top to bottom)movement of subducting slabs,it collectively forms the primary upward and downward channels for the transport of materials and energy between the Earth's surface and the deep mantle,leading to intense volcanic activities and climatic-environmental effects on the surface.The establishment and refinement of the mantle plume model have undergone a relatively long process,during which a series of significant papers have been produced.We have selected six typically representative papers from these works for interpretation,aiming to present to readers the key records of the mantle plume model,including its establishment,verification,and associated effects.These papers cover the following aspects:the proposal of the mantle plume model,the establishment of the“head-tail”morphology of mantle plumes,the constraints of geochemical observations on the chemical composition of mantle plumes,the constraints of seismological observations on the morphological structure of mantle plumes,the surface manifestations of mantle plumes,and the impacts of mantle plumes on the Earth's surface environment.From different perspectives,these papers form the cornerstones in the development of the mantle plume model,provide key supporting nodes for this theoretical framework,and offer important insights and references for subsequent research.
基金supported by the National Key R&D Program of China(Grant No.2022YFC3003701)the National Natural Science Foundation of China(Grant No.42274061)。
文摘Transform faults represent one of the three primary types of plate boundaries in plate tectonics theory and constitute an essential component of this framework.In general,they are classified into oceanic and continental transform faults based on the nature of their separated plates.Owing to significant differences in properties between continental and oceanic lithospheres,continental transform faults exhibit more complex structures than their oceanic counterparts.Continental transform faults are strike-slip boundaries where stress and strain are highly concentrated.They typically extend for hundreds to thousands of kilometers and have experienced tens to hundreds of kilometers of strike-slip displacement.These faults may appear as a single master fault or as complex fault systems with multiple branches.Their deep structures and deformation patterns at varying depths offer critical insights into the structure and rheological behavior of the continental lithosphere.Imaging fine-scale structures of continental transform faults via geophysical methods is crucial for understanding their nature and evolution.Seismic anisotropy results provide key constraints on their deep deformation characteristics.This paper reviews geophysical studies from typical continental transform fault regions and investigates their deep structure and deformation mechanisms by integrating geological and geodetic observations.Although these fault systems are structurally diverse,several common features emerge.(1)Nearly all continental transform faults cut through the entire crust and extend into the upper mantle,with significant seismic anisotropy observed within the fault zones.(2)Regardless of whether the fault is a single narrow structure or a branching system,uppercrustal segments typically form narrow zones of strain concentration where brittle friction accommodates slip and seismicity is concentrated.The shear zone broadens with depth,reaching tens of kilometers in width within the lithospheric mantle.(3)The width of a continental transform fault correlates with the nature of the lithosphere it cross-cuts.Narrow shear zones form in rigid and ancient lithosphere,otherwise,broader distributed deformation occurs.(4)Non-strike-slip components(compression or tension)significantly influence fault zone complexity.Recent ocean drilling programs have advanced understanding of oceanic transform faults,yet knowledge of continental transform fault structure and evolution remains limited.Advances in seismic imaging and observational techniques will enable higher-resolution characterization of these faults,providing new constraints on their seismic behavior and earthquake migration patterns.
基金funded by National Science Foundation of China(No.42025401)the Projects of International Cooperation and Exchanges NSFC(42361134580,42311530062).
文摘The discrimination test of ambiguity resolution,also known as ambiguity validation,is a vital procedure to quantify the reliability of Global Navigation Satellite System(GNSS)ambiguity-fixed solutions.Several well-known tests,including the R-ratio,W-ratio,and Ambiguity Dilution of Precision,usually employ empirical thresholds for the discrimination of integer candidates.We aim at improving the reliability of ambiguity validation by integrating these tests using a machine learning model called the Support Vector Model(SVM).The dataset used consists of simulated real-time Precise Point Positioning Ambiguity Resolution(PPP-AR)solutions in 1-day batch.Specifically,the training dataset is derived using the observations from days 1-31 of year 2023,while the testing dataset is generated using the observations from days 153-159 of years 2022 and 2024.The results reveal that the SVM validates PPP-AR at a success rate of 83%for the independent testing dataset.At the same time,the mean error of the convergence time predicted by the SVM is about 1.0 min,whereas that by the R-ratio test up to 5.0 min.A vehicle-borne experiment conducted on day 362 of year 2020 further demonstrates the improvement of this method in a kinematic scenario,with a success rate of 92%compared to 82%with the conventional R-ratio test.
基金supported by the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology(Grant No.2024yjrc64)the National Natural Science Foundation of China(Grant No.42230101)the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(Grant No.2025ZD1004903)。
文摘Surface wave tomography based on dispersion is an important approach for imaging the velocity structure of the Earth's crust and upper mantle.Traditional surface wave tomography methods based on dispersion data typically involve a multistep process:initial construction of 2D phase/group velocity maps,a point-wise inversion of dispersion data to derive 1D profiles of shear wave velocity as a function of depth at each grid point,and final construction of the 3D velocity model.However,conventional 2D tomography methods have certain limitations.For instance,linearized inversion methods are highly sensitive to the choice of the initial velocity model and regularization parameters,while eikonal tomography method requires dense observations.Here,we propose a surface wave tomography method based on physics-informed neural networks,which can construct the phase/group velocity maps of multiple measurement periods simultaneously,eliminating the need for repeated individual inversions for each period.The network comprises two branches,one taking in the coordinates of the virtual source and station as well as period as input to fit the observed surface wave travel times,and another one taking in the station coordinates and period to predict the phase/group velocity.The two branches are constrained by the eikonal equation.After the training is completed,the velocity of each grid point in each period can be queried using the neural network and form the phase/group velocity maps.We test the new method using data from the Feidong and the Weifang dense seismic arrays deployed around the Tanlu Fault Zone in eastern China,and compare the tomography results with those of the traditional method.We demonstrate that the new method is a meshless tomography approach with data adaptive resolution.In addition,it does not require an initial velocity model or explicit regularizations.This method is highly automated,simple,and user-friendly,and it has great potential for integration with existing automatic dispersion curve extraction techniques to achieve automated surface wave tomography without human intervention.
基金supported by the National Key Research and Development Program of China(Grant No.2024YFF0807300)the National Natural Science Foundation of China(Grant Nos.42474087,42325401,42488301)the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(Grant No.GPMR202447)。
文摘Radial anisotropy structures are essential for understanding tectonic stress fields and distinguishing between lowvelocity zones(LVZs)associated with sedimentary basins and fault damage zones,offering critical insights for comprehensive seismic hazard assessments.This study employed ambient noise tomography to investigate the fault zone and surrounding structures of the Chenghai Fault in the Binchuan Basin,Yunnan Province,China.Utilizing three-component waveform data collected from a linear dense seismic array consisting of 114 stations,we constructed a high-resolution shear wave velocity and radial anisotropy model.Our results reveal notable variations in radial anisotropy across the study region,with pronounced negative radial anisotropy surrounding the Chenghai Fault,likely reflecting fault damage.In contrast,positive radial anisotropy is observed beneath the Dongshan Mountain,indicative of extensional stress.The LVZ beneath the Binchuan Basin exhibits positive radial anisotropy,suggesting that this LVZ is primarily due to sedimentary deposits.Based on the shear wave velocity and radial anisotropy structure,we infer that the Chenghai Fault,influenced by east-west extensional tectonics,behaves as a high-angle normal fault.Additionally,another fault with a relatively lower dip angle is identified within the Binchuan Basin.The tectonic activity of the Chenghai Fault played a significant role in the initiation of sedimentation within the Binchuan Basin during the Neogene period.These findings are crucial for advancing the understanding of fault dynamics and provide essential insights for refining seismic hazard assessments in the region.
基金supported by the National Key Research and Development Project of China(Grant No.2021YFC3000600)the National Natural Science Foundation of China(Grant Nos.U2139204,42488301)。
文摘The Sichuan-Yunnan region hosts numerous large active faults with complex spatial distributions and intricate intersections,where moderate-to-strong earthquakes occur frequently.Obtaining source mechanism solutions for these earthquakes is not only essential for analyzing the regional crustal stress regime,fault geometries,activity behaviors and seismic potentials,but also is critical for assessing seismic hazards.Previous studies have obtained source mechanism catalogs of regional historical moderate-to-strong earthquakes based on 1D crustal velocity models,or inverted source mechanisms for few representative events based on 3D velocity models incorporating lateral variations.However,a systematic source mechanism inversion framework,which integrates regional high-resolution 3D velocity models with significant topographic relief,still remains absent for the Sichuan-Yunnan region.Using the high-resolution 3D velocity model SWChinaCVM-2.0 with regional topographic relief,we first construct a comprehensive strain Green's tensor library for the 181 permanent broadband seismic stations across the Sichuan-Yunnan region.In particular,the forward modeling employs the spectral element method(SEM)with source-receiver reciprocity,followed by highly efficient compression of the computed library.Subsequently,a systematic source mechanism inversion is conducted for the 563 M_(L)≥4 earthquakes occurring in the region during 2009-2021 using full waveform matching.With the derived solutions of fault planes,full moment tensors and moment magnitudes,a new-generation,accurate source mechanism catalog for moderate-to-strong earthquakes in the Sichuan-Yunnan region is obtained.This catalog can provide essential data for future geoscience studies in the Sichuan-Yunnan region,and is a foundational geophysical work driven by new techniques and methods.In the future,the inversion framework can also be applied to areas with high seismic risks such as North China and Xinjiang,providing essential supports for rapid and accurate determination of source parameters and assessment of seismic hazards.
