The distribution of Coulomb failure stress （CFS） change in the steep excavation slope is calculated by finite element method in this paper, and the failure mechanics under different conditions have been investigated...The distribution of Coulomb failure stress （CFS） change in the steep excavation slope is calculated by finite element method in this paper, and the failure mechanics under different conditions have been investigated. Comparing the CFSs before and after the slope excavation （stress loading and unloading processes）, the dangerous internal zone and the most likely failure external area are attained. Given the shear cracks on the top surface while tensile stress or cracks along the toe of the slope, we analyze the high cutting-angle steep slope in Kaixian county of the Three Gorges Reservoir region. We bring forward that the peak value of CFS after excavation can reach to the order of 0.1 MPa, which is greatly higher than that of before. Our preliminary results are useful for optimizing the reinforcement structure during the steep slope stabilization engineering.展开更多
A new combined Fermi, betatron, and turbulent electron acceleration mechanism is proposed in interaction of magnetic islands during turbulent magnetic reconnection evolution in explosive astrophysical phenomena at lar...A new combined Fermi, betatron, and turbulent electron acceleration mechanism is proposed in interaction of magnetic islands during turbulent magnetic reconnection evolution in explosive astrophysical phenomena at large temporal-spatial scale(LTSTMR), the ratio of observed current sheets thickness to electron characteristic length, electron Larmor radius for low-β and electron inertial length for high-β, is on the order of 10^(10)–10^(11); the ratio of observed evolution time to electron gyroperiod is on the order of 10~7–10~9).The original combined acceleration model is known to be one of greatest importance in the interaction of magnetic islands; it assumes that the continuous kinetic-dynamic temporal-spatial scale evolution occurs as two separate independent processes.In this paper, we reconsider the combined acceleration mechanism by introducing a kinetic-dynamic-hydro full-coupled model instead of the original micro-kinetic or macro-dynamic model.We investigate different acceleration mechanisms in the vicinity of neutral points in magnetic islands evolution, from the stage of shrink and breakup into smaller islands(kinetic scale), to the stage of coalescence and growth into larger islands(dynamic scale), to the stages of constant and quasi-constant(contracting-expanding) islands(hydro scale).As a result, we give for the first time the acceleration efficiencies of different types of acceleration mechanisms in magnetic islands' interactions in solar atmosphere LTSTMR activities(pico-, 10^(–2)–10~5 m; nano-, 10~5–10~6 m; micro-, 10~6–10~7 m; macro-, 10~7–10~8 m; large-,10~8–10~9 m).展开更多
The dense broadband seismic network provides more high-quality waveform that is helpful to improve constraint focal depth of shallow earthquake. Many shal- low earthquakes occurring in sediment were regarded as induce...The dense broadband seismic network provides more high-quality waveform that is helpful to improve constraint focal depth of shallow earthquake. Many shal- low earthquakes occurring in sediment were regarded as induced events. In Sichuan basin, gas industry and salt mining are dependent on fluid injection technique that triggers microseismicity. We method with regional records adopted waveform inversion to obtain focal mechanism of an Ms4.8 earthquake at Changning. The result suggested that the Changning earthquake occurred at a ESE thrust fault, and its focal depth was about 3 km. The depth phases including teleseismic pP phase and regional sPL phase shows that the focal depth is about 2 km. The strong, short- period surface wave suggests that this event is a very shallow earthquake. The amplitude ratio between Rayleigh wave and direct S wave was also used to estimate the source depth of the mainshock. The focal depth （2-4 km） is far less than the depth of the sedimentary layer thickness （6-8 km） in epicentral region. It is close to the depth of fluid injection of salt mining, which may imply that this event was triggered by the industrial activity.展开更多
Can earthquakes be predicted？ How should people overcome the difficulties encountered in the study of earthquake prediction？ This issue can take inspiration from the experiences of weather forecast. Although weather...Can earthquakes be predicted？ How should people overcome the difficulties encountered in the study of earthquake prediction？ This issue can take inspiration from the experiences of weather forecast. Although weather forecasting took a period of about half a century to advance from empirical to numerical forecast, it has achieved significant success. A consensus has been reached among the Chinese seismological community that earth- quake prediction must also develop from empirical fore- casting to physical prediction. However, it is seldom mentioned that physical prediction is characterized by quantitatively numerical predictions based on physical laws. This article discusses five key components for numerical earthquake prediction and their current status. We conclude that numerical earthquake prediction should now be put on the planning agenda and its roadmap designed, seismic stations should be deployed and observations made according to the needs of numerical prediction, and theoretical research should be carried out.展开更多
Taiwan is a young orogenic belt with complex spatial distributions of deformation and earthquakes. We have constructed a three-dimensional finite element model to explore how the interplays between lithospheric struc-...Taiwan is a young orogenic belt with complex spatial distributions of deformation and earthquakes. We have constructed a three-dimensional finite element model to explore how the interplays between lithospheric struc- ture and plate boundary processes control the distribution of stress and strain rates in the Taiwan region. The model assumes a liberalized power-law rheology and incorporates main lithospheric structures; the model domain is loaded by the present-day crustal velocity applied at its bound- aries. The model successfully reproduces the main features of the GPS-measured strain rate patterns and the earth- quake-indicated stress states in the Taiwan region. The best fitting model requires the viscosity of the lower crust to be two orders of magnitude lower than that of the upper crust and lithospheric mantle. The calculated deviatoric stress is high in regions of thrust faulting and low in regions of extensional and strike-slip faulting, consistent with the spatial pattern of seismic intensity in Taiwan.展开更多
There are 13 papers in this special issue on stress field, crustal deformation and seismicity. The great Wenchuan earthquake is a grievous disaster, but Chinese scientists are trying to learn more from the event in or...There are 13 papers in this special issue on stress field, crustal deformation and seismicity. The great Wenchuan earthquake is a grievous disaster, but Chinese scientists are trying to learn more from the event in order to understand better the physics of earthquakes for future hazard mitigation planning. Rapid development of GPS technology provide the possibility in the first time in history to monitor the crustal deformation in a wide range and high accuracy, however, it is an important lesson learned from the Wenchuan earthquake,展开更多
A mantle thermal plume may be tilted,deflected,or even split-up by mantle lateral flows(mantle wind)during its ascent,which in turn changes the spatial distribution of various geological-magmatic responses,such as mag...A mantle thermal plume may be tilted,deflected,or even split-up by mantle lateral flows(mantle wind)during its ascent,which in turn changes the spatial distribution of various geological-magmatic responses,such as magmatic activity in the overriding plate and hotspot tracks on the surface,affecting the reliability of the constraints on absolute plate motion history.Previous research on tilted mantle plumes has focused mainly on the lower/whole mantle regions.Whether mantle plumes formed in whole/layered mantle convection suffer lateral tilt in the upper mantle,and how this affects the magmatic activity along the surface hotspot track as well as the plume-related tectonic processes,are important scientific issues in mantle thermalplume dynamics and plate tectonics theory.This study introduces a thermal Stokes-fluid-dynamics numerical model(in ASPECT software)and pyrolite parameters constrained by mineral physics data,and quantitatively analyzes the tilted/deflected morphology of upper-mantle plumes and the concomitant surface-hotspot location-evolution characteristics under the combined effects of overriding-plate-motion driven flow(Couette)and upper mantle counter-flow(Poiseuille).We find that this composite upper-mantle wind can lead to(1)Plume head-and-upper-conduit horizontal motion in the opposite direction of the overriding plate motion and also with respect to the conduit roots,such that the magmatic spacing is increased;(2)Near-periodic split-up and ascent of a laterally-moving plume conduit,whose split-up/ascent period depends mainly on the thermo-chemical buoyancy of the plume itself;and(3)Under specific conditions of thermo-chemical buoyancy of a main“parent”plume interacting with upper mantle winds,two secondary“child”plumes hundreds of kilometers apart can sprout and ascend sequentially/subsimultaneously through the upper mantle in a very short period of time(2–4 Myr).The resulting oscillating/jumping behavior of hotspot locations along the overriding plate motion direction can be used to explain the observations on some of Earth's igneous provinces and hotspot tracks(for example,the Kerguelen hotspot)and related-tectonics,that:(i)younger hotspot-magmatictectonic regions can superimpose-to and situate-amidst older ones(surface-hotspot-motion or plume-deflection distances greater than overriding-plate-motion distances,with magmatism separated closely in space but largely in time),and(ii)plume-related magmatism can be widely separated in space but closely in time or age(near-simultaneous ascent of two distant“child”plumes from the same“parent”mantle-plume conduit).Our study suggests that the complex dynamic environment within the upper mantle should be considered when constraining absolute plate motions by the moving-hotspot-reference-frame,especially when these hotspots are located near mid-ocean ridges and/or subduction zones.展开更多
1.Introduction.On November 23,2017,an M_(S)5.0 earthquake occurred in Wulong,Chongqing,China,resulting in tens of casualties and considerable economic loss.Geologically,the epicenter of this earthquake was located in ...1.Introduction.On November 23,2017,an M_(S)5.0 earthquake occurred in Wulong,Chongqing,China,resulting in tens of casualties and considerable economic loss.Geologically,the epicenter of this earthquake was located in the transition zone from the Central Chongqing Fold Belt to the southeast,characterized by a low tectonic loading rate.展开更多
The analysis of seismic hazards relies on the statistical analysis of historical seismic data and the instrumental seismic catalog to obtain the regional earthquake recurrence interval and earthquake probability.The a...The analysis of seismic hazards relies on the statistical analysis of historical seismic data and the instrumental seismic catalog to obtain the regional earthquake recurrence interval and earthquake probability.The accuracy of analysis thus depends strongly on the completeness of the seismic data used.However,available seismic catalogs are too short or incomplete for the reliable analysis of the statistical characteristics of earthquakes.If a long-term synthetic seismic catalog can be generated using a physics-based numerical simulation,and the simulation results match the crustal deformation,seismicity,and other observations,then such a synthetic catalog helps us to further understand the characteristics of seismic activity and analyze the regional seismic hazard.In this paper,taking the northeastern Tibetan Plateau as a case study,we establish a three-dimensional visco-elastoplastic finite-element model to simulate earthquake cycles and the spatiotemporal evolution of earthquakes on the model fault system and obtain a seismic catalog on a time scale of tens of thousands of years.On the basis that the model satisfies the regional geodynamics of the northeastern Tibetan Plateau,we analyze seismicity on the northeastern Tibetan Plateau using the simulated synthetic earthquake catalog.The characteristics of earthquake recurrence at different locations and different magnitudes,and the long-term average probability of earthquake occurrence within the fault system on the northeastern Tibetan plateau are studied.The results are a reference for regional seismic hazard assessment and provide a basis for the physics-based numerical prediction of earthquakes.展开更多
China has planned and built several world-class cascade high dams in Jinsha River,Dadu River,Lancang River,and Yarlung Zangbo River.The complex geological conditions in the reservoir area and numerous large-scale land...China has planned and built several world-class cascade high dams in Jinsha River,Dadu River,Lancang River,and Yarlung Zangbo River.The complex geological conditions in the reservoir area and numerous large-scale landslide bodies make the potential disaster risk of overflowing and cascade dam failure caused by landslide-generated tsunami under increasing severe situations.However,the study on describing and predicting the complex dynamic processes of generation,propagation,overflowing,wave setup,and the interaction between tsunami and lakeshore has not been systematically carried out.Based on the high-order Boussinesq-type equations,the development of the dynamic system of tsunamis in lakes coupled with the landslide process is realized using the finite volume method in this paper.To verify the accuracy and reliability of the study,the Xiluodu Reservoir is selected as the object to simulate the potential landslide-generated tsunamis.The factors such as the generation and propagation of tsunamis,dam overflowing,and wave setup in the downstream river are quantitatively evaluated and analyzed.The constructed landslide with a total volume of 24×10^(6)m^(3)generates a near-field wave amplitude of about 28 m.The maximum wave run-up height is about 95 m,the volume of the dam overflowing water up to 2.13×10^(6)m^(3),and the maximum wave height above the dam crest presents an M-shaped distribution.This LGWs event raises the downstream water level by nearly 40 m.The results show that the risk of landslide-generated tsunamis in the reservoir area in China cannot be ignored.The developed Boussinesq-type equations coupled with the landslide dynamics can simulate the whole process of generation,propagation,runup,and estimating the overflowing water volume of the tsunamis in the lake,laying a foundation for the quantitative risk assessment of tsunamis in lakes of high cascade dams in China.展开更多
Based on focused ion beam and shear friction apparatus data, the multi-resolutions （0.2 nm-5μm） volume roughness ＆ asperity contact （VR ＆ AC） three-dimensional structure on principle slip surface interface-surf...Based on focused ion beam and shear friction apparatus data, the multi-resolutions （0.2 nm-5μm） volume roughness ＆ asperity contact （VR ＆ AC） three-dimensional structure on principle slip surface interface-surface （PSS-IS） is measured on high performance computational platform; and physical plastic-creep friction model is established by using hybrid hyper-singular integral equation ＆ lattice Boltzmann ＆ lattice Green function （BE-LB-LG）. The correlation of rheological property and VR ＆ AC evolution under transient （10 μs） macro-normal stress （18-300 MPa） and slip rate （0.25-7.5 m/s） are obtained; and the PSS-IS friction in co-seismic flash heating is quantitative analyzed for the first time.展开更多
Describing the correlation of a reservoir and earthquake slip remains a great challenge. Professor SHI Yaolin and his group at the Key Laboratory of Computational Geodynamics of the Chinese Academy of Sciences and the...Describing the correlation of a reservoir and earthquake slip remains a great challenge. Professor SHI Yaolin and his group at the Key Laboratory of Computational Geodynamics of the Chinese Academy of Sciences and the College of Science of the Graduate University of the Chinese Academy of Sciences are attempting to solve this problem. On the basis of the laboratory's parallel central processing unit (CPU)展开更多
A series of large strike-slip and thrust faults have developed in the northeastern margin of the Tibetan Plateau since the Late Cenozoic,with strong and active tectonic activity and frequent occurrences of large earth...A series of large strike-slip and thrust faults have developed in the northeastern margin of the Tibetan Plateau since the Late Cenozoic,with strong and active tectonic activity and frequent occurrences of large earthquakes.Modulation of regional tectonic stress distribution,strain fields,and seismic hazards has not been well studied.This study introduces a three-dimensional viscoelastic finite element numerical model to calculate crustal stress and strain rate fields under current tectonic loading.The preliminary results show that the direction of the horizontal principal compressive stress rate and compressive horizontal principal strain rate in the northeastern margin of the Tibetan Plateau rotate clockwise as a whole,and this rotation is more significant in the southeast direction because of the block of the Alxa and the Ordos blocks.The NE-SW horizontal principal compressive stress rate and SE horizontal tensile stress rate dominate the entire study region.The maximum value of the horizontal principal compressive strain rate at a depth of 0 km in the model is approximately 4×10^(-8)yr^(-1)near the East Kunlun fault and is smaller in the stable Alxa and Ordos blocks at approximately 1×10^(-8)yr^(-1).The calculated regional stress state is in good agreement with the actual focal mechanism solution,indicating that strike-slip and thrust stress fields dominate the northeastern margin of the Tibetan Plateau.The Altyn Tagh,East Kunlun,and Haiyuan faults demonstrate that the maximum shear strain rate gradually decreases eastward,and the decrease in the maximum shear strain rate value is absorbed by orogenic uplift and crustal shortening at its boundaries.The western section of the Altyn Tagh fault,west-to-middle sections of the East Kunlun fault,and west-to-middle sections of the Haiyuan fault will have high seismic hazards in the future.展开更多
Under the shadow of the far-field effect of the India-Eurasia collision,the Tianshan orogenic belt underwent tectonic re-activation in the Cenozoic,accompanied by strong tectonic deformation and frequent large earthqu...Under the shadow of the far-field effect of the India-Eurasia collision,the Tianshan orogenic belt underwent tectonic re-activation in the Cenozoic,accompanied by strong tectonic deformation and frequent large earthquakes.Bounded by two rigid cratonic blocks located in its north and south,a series of marginal foreland fold-and-thrust belts are developed within the Tianshan orogenic belt and continue to develop to the bilateral pull-apart basins.Meanwhile,the faults in the orogenic belt are reactivated.The deformation caused by thrust-related structure accounts for larger than 50%of the total convergence of the Tianshan Mountains,which results in the most active structure with large earthquakes in the Tianshan area.Therefore,it is of great significance to study the dynamic process of the newly generated and reactivated thrust-nappe structures in Tianshan orogen via numerical modeling.This paper selects a classical cross-section profile in the western segment of the Southwest Tianshan Mountains,which contains the Kalpin-Maidan-Nalati-Kemin fault system from the south to the north.We attempt to establish a two-dimensional plane strain,viscoelastic finite element model,by treating the regional faults as a whole fault system and considering the topography,fault geometry,and GPS data.The displacement and stress fields of the model are retrieved,the short-term cumulative deformation field of the overall fault system is analyzed,and the rate of Coulomb failure stress change of each fault is also considered.The results show that the deformation is concentrated in the middle and southern parts of the Southwest Tianshan Mountains.In contrast,the deformation of the Kemin fault in the north is relatively small.According to the Coulomb failure stress changes of these four faults and the historical earthquake catalog,the potential seismicity of each fault is qualitatively analyzed.Our preliminary results suggest that the possibility of large earthquake occurrence is higher in the Kalpin fault,Maidan fault,and Nalati fault but lower in the Kemin fault in the near future。展开更多
基金supported by Sinoprob-Deep Exploration Program in China sponsored by Ministry of Land and Resources of the People’s Republic of China (No.0819011A90)National Natural Science Foundation of China (No.D0408/4097409)
文摘The distribution of Coulomb failure stress （CFS） change in the steep excavation slope is calculated by finite element method in this paper, and the failure mechanics under different conditions have been investigated. Comparing the CFSs before and after the slope excavation （stress loading and unloading processes）, the dangerous internal zone and the most likely failure external area are attained. Given the shear cracks on the top surface while tensile stress or cracks along the toe of the slope, we analyze the high cutting-angle steep slope in Kaixian county of the Three Gorges Reservoir region. We bring forward that the peak value of CFS after excavation can reach to the order of 0.1 MPa, which is greatly higher than that of before. Our preliminary results are useful for optimizing the reinforcement structure during the steep slope stabilization engineering.
基金supported by the strategic priority research program of CAS (XDA17040507, XDA15010900)the national basic research program of China (2013CBA01503)+5 种基金the key program of NSFC (11333007)joint funds of NSFC(U1631130)frontier science key programs of CAS (QYZDJ-SSWSLH012)the program for innovation team of Yunnan Provincethe program for Guangdong introducing Innovative and entrepreneurial teams (2016ZT06D211)the special program for applied research on super computation of the NSFC-Guangdong joint fund (second phase) under No.U1501501
文摘A new combined Fermi, betatron, and turbulent electron acceleration mechanism is proposed in interaction of magnetic islands during turbulent magnetic reconnection evolution in explosive astrophysical phenomena at large temporal-spatial scale(LTSTMR), the ratio of observed current sheets thickness to electron characteristic length, electron Larmor radius for low-β and electron inertial length for high-β, is on the order of 10^(10)–10^(11); the ratio of observed evolution time to electron gyroperiod is on the order of 10~7–10~9).The original combined acceleration model is known to be one of greatest importance in the interaction of magnetic islands; it assumes that the continuous kinetic-dynamic temporal-spatial scale evolution occurs as two separate independent processes.In this paper, we reconsider the combined acceleration mechanism by introducing a kinetic-dynamic-hydro full-coupled model instead of the original micro-kinetic or macro-dynamic model.We investigate different acceleration mechanisms in the vicinity of neutral points in magnetic islands evolution, from the stage of shrink and breakup into smaller islands(kinetic scale), to the stage of coalescence and growth into larger islands(dynamic scale), to the stages of constant and quasi-constant(contracting-expanding) islands(hydro scale).As a result, we give for the first time the acceleration efficiencies of different types of acceleration mechanisms in magnetic islands' interactions in solar atmosphere LTSTMR activities(pico-, 10^(–2)–10~5 m; nano-, 10~5–10~6 m; micro-, 10~6–10~7 m; macro-, 10~7–10~8 m; large-,10~8–10~9 m).
基金supported by China National Special Fund for Earthquake Scientific Research in Public Interest (201308013)China Postdoctoral Science Foundation (No. 2012M520431)the National Natural Science Foundation of China Grant No. 41204044
文摘The dense broadband seismic network provides more high-quality waveform that is helpful to improve constraint focal depth of shallow earthquake. Many shal- low earthquakes occurring in sediment were regarded as induced events. In Sichuan basin, gas industry and salt mining are dependent on fluid injection technique that triggers microseismicity. We method with regional records adopted waveform inversion to obtain focal mechanism of an Ms4.8 earthquake at Changning. The result suggested that the Changning earthquake occurred at a ESE thrust fault, and its focal depth was about 3 km. The depth phases including teleseismic pP phase and regional sPL phase shows that the focal depth is about 2 km. The strong, short- period surface wave suggests that this event is a very shallow earthquake. The amplitude ratio between Rayleigh wave and direct S wave was also used to estimate the source depth of the mainshock. The focal depth （2-4 km） is far less than the depth of the sedimentary layer thickness （6-8 km） in epicentral region. It is close to the depth of fluid injection of salt mining, which may imply that this event was triggered by the industrial activity.
基金supported by the CAS/CAFEA international partnership Program for creative research teams (No.KZZD-EW-TZ-19)China National Science and Technology Support Program ‘‘Practical Techniques for Earthquake Analysis and Prediction Research’’ 2012BAK19B03-5
文摘Can earthquakes be predicted？ How should people overcome the difficulties encountered in the study of earthquake prediction？ This issue can take inspiration from the experiences of weather forecast. Although weather forecasting took a period of about half a century to advance from empirical to numerical forecast, it has achieved significant success. A consensus has been reached among the Chinese seismological community that earth- quake prediction must also develop from empirical fore- casting to physical prediction. However, it is seldom mentioned that physical prediction is characterized by quantitatively numerical predictions based on physical laws. This article discusses five key components for numerical earthquake prediction and their current status. We conclude that numerical earthquake prediction should now be put on the planning agenda and its roadmap designed, seismic stations should be deployed and observations made according to the needs of numerical prediction, and theoretical research should be carried out.
基金supported by the National Natural Science Foundation of China(No.41204066)China Geological Survey(Nos.12120114002101,12120114002401)+1 种基金Deep Exploration in China(SinoProbe-08-01,SinoProbe-07)the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘Taiwan is a young orogenic belt with complex spatial distributions of deformation and earthquakes. We have constructed a three-dimensional finite element model to explore how the interplays between lithospheric struc- ture and plate boundary processes control the distribution of stress and strain rates in the Taiwan region. The model assumes a liberalized power-law rheology and incorporates main lithospheric structures; the model domain is loaded by the present-day crustal velocity applied at its bound- aries. The model successfully reproduces the main features of the GPS-measured strain rate patterns and the earth- quake-indicated stress states in the Taiwan region. The best fitting model requires the viscosity of the lower crust to be two orders of magnitude lower than that of the upper crust and lithospheric mantle. The calculated deviatoric stress is high in regions of thrust faulting and low in regions of extensional and strike-slip faulting, consistent with the spatial pattern of seismic intensity in Taiwan.
文摘There are 13 papers in this special issue on stress field, crustal deformation and seismicity. The great Wenchuan earthquake is a grievous disaster, but Chinese scientists are trying to learn more from the event in order to understand better the physics of earthquakes for future hazard mitigation planning. Rapid development of GPS technology provide the possibility in the first time in history to monitor the crustal deformation in a wide range and high accuracy, however, it is an important lesson learned from the Wenchuan earthquake,
基金supported by the National Key Scientific and Technological Infrastructure project“Earth System Science Numerical Simulator Facility”(EarthLab)supported by the National Natural Science Foundation of China(Grant Nos.U2239205,41725017)。
文摘A mantle thermal plume may be tilted,deflected,or even split-up by mantle lateral flows(mantle wind)during its ascent,which in turn changes the spatial distribution of various geological-magmatic responses,such as magmatic activity in the overriding plate and hotspot tracks on the surface,affecting the reliability of the constraints on absolute plate motion history.Previous research on tilted mantle plumes has focused mainly on the lower/whole mantle regions.Whether mantle plumes formed in whole/layered mantle convection suffer lateral tilt in the upper mantle,and how this affects the magmatic activity along the surface hotspot track as well as the plume-related tectonic processes,are important scientific issues in mantle thermalplume dynamics and plate tectonics theory.This study introduces a thermal Stokes-fluid-dynamics numerical model(in ASPECT software)and pyrolite parameters constrained by mineral physics data,and quantitatively analyzes the tilted/deflected morphology of upper-mantle plumes and the concomitant surface-hotspot location-evolution characteristics under the combined effects of overriding-plate-motion driven flow(Couette)and upper mantle counter-flow(Poiseuille).We find that this composite upper-mantle wind can lead to(1)Plume head-and-upper-conduit horizontal motion in the opposite direction of the overriding plate motion and also with respect to the conduit roots,such that the magmatic spacing is increased;(2)Near-periodic split-up and ascent of a laterally-moving plume conduit,whose split-up/ascent period depends mainly on the thermo-chemical buoyancy of the plume itself;and(3)Under specific conditions of thermo-chemical buoyancy of a main“parent”plume interacting with upper mantle winds,two secondary“child”plumes hundreds of kilometers apart can sprout and ascend sequentially/subsimultaneously through the upper mantle in a very short period of time(2–4 Myr).The resulting oscillating/jumping behavior of hotspot locations along the overriding plate motion direction can be used to explain the observations on some of Earth's igneous provinces and hotspot tracks(for example,the Kerguelen hotspot)and related-tectonics,that:(i)younger hotspot-magmatictectonic regions can superimpose-to and situate-amidst older ones(surface-hotspot-motion or plume-deflection distances greater than overriding-plate-motion distances,with magmatism separated closely in space but largely in time),and(ii)plume-related magmatism can be widely separated in space but closely in time or age(near-simultaneous ascent of two distant“child”plumes from the same“parent”mantle-plume conduit).Our study suggests that the complex dynamic environment within the upper mantle should be considered when constraining absolute plate motions by the moving-hotspot-reference-frame,especially when these hotspots are located near mid-ocean ridges and/or subduction zones.
基金support provided by the National Major Scientific and Technological Infrastructure Project“Numerical Simulator for Earth System”supported by the National Natural Science Foundation of China(Grant No.U2239205)the Open Fund of the State Key Laboratory of Geodesy and Earth’s Dynamics(Grant No.SKLGED2023-4-2)。
文摘1.Introduction.On November 23,2017,an M_(S)5.0 earthquake occurred in Wulong,Chongqing,China,resulting in tens of casualties and considerable economic loss.Geologically,the epicenter of this earthquake was located in the transition zone from the Central Chongqing Fold Belt to the southeast,characterized by a low tectonic loading rate.
基金supported by China Earthquake Science Experiment Project,CEA(Grant No.2019CSES0112)National Natural Science Foundation of China(Grant Nos.41574085,41974107,41590865&U1839207)。
文摘The analysis of seismic hazards relies on the statistical analysis of historical seismic data and the instrumental seismic catalog to obtain the regional earthquake recurrence interval and earthquake probability.The accuracy of analysis thus depends strongly on the completeness of the seismic data used.However,available seismic catalogs are too short or incomplete for the reliable analysis of the statistical characteristics of earthquakes.If a long-term synthetic seismic catalog can be generated using a physics-based numerical simulation,and the simulation results match the crustal deformation,seismicity,and other observations,then such a synthetic catalog helps us to further understand the characteristics of seismic activity and analyze the regional seismic hazard.In this paper,taking the northeastern Tibetan Plateau as a case study,we establish a three-dimensional visco-elastoplastic finite-element model to simulate earthquake cycles and the spatiotemporal evolution of earthquakes on the model fault system and obtain a seismic catalog on a time scale of tens of thousands of years.On the basis that the model satisfies the regional geodynamics of the northeastern Tibetan Plateau,we analyze seismicity on the northeastern Tibetan Plateau using the simulated synthetic earthquake catalog.The characteristics of earthquake recurrence at different locations and different magnitudes,and the long-term average probability of earthquake occurrence within the fault system on the northeastern Tibetan plateau are studied.The results are a reference for regional seismic hazard assessment and provide a basis for the physics-based numerical prediction of earthquakes.
基金supported by the National Natural Science Foundation of China(Grant No.41725017)the National Key R&D Program of the Ministry of Science and Technology of China(Grant No.2020YFA0713401)the National Natural Science Foundation of China(Grant No.U1839207)。
文摘China has planned and built several world-class cascade high dams in Jinsha River,Dadu River,Lancang River,and Yarlung Zangbo River.The complex geological conditions in the reservoir area and numerous large-scale landslide bodies make the potential disaster risk of overflowing and cascade dam failure caused by landslide-generated tsunami under increasing severe situations.However,the study on describing and predicting the complex dynamic processes of generation,propagation,overflowing,wave setup,and the interaction between tsunami and lakeshore has not been systematically carried out.Based on the high-order Boussinesq-type equations,the development of the dynamic system of tsunamis in lakes coupled with the landslide process is realized using the finite volume method in this paper.To verify the accuracy and reliability of the study,the Xiluodu Reservoir is selected as the object to simulate the potential landslide-generated tsunamis.The factors such as the generation and propagation of tsunamis,dam overflowing,and wave setup in the downstream river are quantitatively evaluated and analyzed.The constructed landslide with a total volume of 24×10^(6)m^(3)generates a near-field wave amplitude of about 28 m.The maximum wave run-up height is about 95 m,the volume of the dam overflowing water up to 2.13×10^(6)m^(3),and the maximum wave height above the dam crest presents an M-shaped distribution.This LGWs event raises the downstream water level by nearly 40 m.The results show that the risk of landslide-generated tsunamis in the reservoir area in China cannot be ignored.The developed Boussinesq-type equations coupled with the landslide dynamics can simulate the whole process of generation,propagation,runup,and estimating the overflowing water volume of the tsunamis in the lake,laying a foundation for the quantitative risk assessment of tsunamis in lakes of high cascade dams in China.
文摘Based on focused ion beam and shear friction apparatus data, the multi-resolutions （0.2 nm-5μm） volume roughness ＆ asperity contact （VR ＆ AC） three-dimensional structure on principle slip surface interface-surface （PSS-IS） is measured on high performance computational platform; and physical plastic-creep friction model is established by using hybrid hyper-singular integral equation ＆ lattice Boltzmann ＆ lattice Green function （BE-LB-LG）. The correlation of rheological property and VR ＆ AC evolution under transient （10 μs） macro-normal stress （18-300 MPa） and slip rate （0.25-7.5 m/s） are obtained; and the PSS-IS friction in co-seismic flash heating is quantitative analyzed for the first time.
文摘Describing the correlation of a reservoir and earthquake slip remains a great challenge. Professor SHI Yaolin and his group at the Key Laboratory of Computational Geodynamics of the Chinese Academy of Sciences and the College of Science of the Graduate University of the Chinese Academy of Sciences are attempting to solve this problem. On the basis of the laboratory's parallel central processing unit (CPU)
基金supported by the National Natural Science Foundation of China for Distinguished Young Scholars(Grant Nos.U2239205,41725017)the National Key Scientific and Technological Infrastructure Project。
文摘A series of large strike-slip and thrust faults have developed in the northeastern margin of the Tibetan Plateau since the Late Cenozoic,with strong and active tectonic activity and frequent occurrences of large earthquakes.Modulation of regional tectonic stress distribution,strain fields,and seismic hazards has not been well studied.This study introduces a three-dimensional viscoelastic finite element numerical model to calculate crustal stress and strain rate fields under current tectonic loading.The preliminary results show that the direction of the horizontal principal compressive stress rate and compressive horizontal principal strain rate in the northeastern margin of the Tibetan Plateau rotate clockwise as a whole,and this rotation is more significant in the southeast direction because of the block of the Alxa and the Ordos blocks.The NE-SW horizontal principal compressive stress rate and SE horizontal tensile stress rate dominate the entire study region.The maximum value of the horizontal principal compressive strain rate at a depth of 0 km in the model is approximately 4×10^(-8)yr^(-1)near the East Kunlun fault and is smaller in the stable Alxa and Ordos blocks at approximately 1×10^(-8)yr^(-1).The calculated regional stress state is in good agreement with the actual focal mechanism solution,indicating that strike-slip and thrust stress fields dominate the northeastern margin of the Tibetan Plateau.The Altyn Tagh,East Kunlun,and Haiyuan faults demonstrate that the maximum shear strain rate gradually decreases eastward,and the decrease in the maximum shear strain rate value is absorbed by orogenic uplift and crustal shortening at its boundaries.The western section of the Altyn Tagh fault,west-to-middle sections of the East Kunlun fault,and west-to-middle sections of the Haiyuan fault will have high seismic hazards in the future.
基金This work was supported by the National Science Foundation for Distinguished Young Scholars(Grant No.41725017)the National Key R&D Program of China(Grant No.2020YFA0713401).
文摘Under the shadow of the far-field effect of the India-Eurasia collision,the Tianshan orogenic belt underwent tectonic re-activation in the Cenozoic,accompanied by strong tectonic deformation and frequent large earthquakes.Bounded by two rigid cratonic blocks located in its north and south,a series of marginal foreland fold-and-thrust belts are developed within the Tianshan orogenic belt and continue to develop to the bilateral pull-apart basins.Meanwhile,the faults in the orogenic belt are reactivated.The deformation caused by thrust-related structure accounts for larger than 50%of the total convergence of the Tianshan Mountains,which results in the most active structure with large earthquakes in the Tianshan area.Therefore,it is of great significance to study the dynamic process of the newly generated and reactivated thrust-nappe structures in Tianshan orogen via numerical modeling.This paper selects a classical cross-section profile in the western segment of the Southwest Tianshan Mountains,which contains the Kalpin-Maidan-Nalati-Kemin fault system from the south to the north.We attempt to establish a two-dimensional plane strain,viscoelastic finite element model,by treating the regional faults as a whole fault system and considering the topography,fault geometry,and GPS data.The displacement and stress fields of the model are retrieved,the short-term cumulative deformation field of the overall fault system is analyzed,and the rate of Coulomb failure stress change of each fault is also considered.The results show that the deformation is concentrated in the middle and southern parts of the Southwest Tianshan Mountains.In contrast,the deformation of the Kemin fault in the north is relatively small.According to the Coulomb failure stress changes of these four faults and the historical earthquake catalog,the potential seismicity of each fault is qualitatively analyzed.Our preliminary results suggest that the possibility of large earthquake occurrence is higher in the Kalpin fault,Maidan fault,and Nalati fault but lower in the Kemin fault in the near future。
