The Paleo-Pacific Plate stagnated in the mantle transition zone beneath northeast Asia during the Late Mesozoic,resulting in the eastern Asian big mantle wedge(BMW).However,its formation mechanism remains unclear.Here...The Paleo-Pacific Plate stagnated in the mantle transition zone beneath northeast Asia during the Late Mesozoic,resulting in the eastern Asian big mantle wedge(BMW).However,its formation mechanism remains unclear.Here,we analyzed elemental and isotopic compositions of 126-60 Ma intraplate basaltic rocks to map the mantle flow pattern and investigate the implications for the formation of the BMW.These rocks exhibit eastward an increase in Ba/Nb,Ba/La,^(87)Sr/^(86)Sr,and^(208)Pb/^(204)Pb ratios,while a decrease in Nb/Yb,Zr/Yb,Ta/Yb,and Nb/Nb*ratios,indicating mixing between the fertile mantle and the depleted mantle modified by slab material,implying the occurrence of trench-perpendicular mantle flow.The coeval mantle flow and formation of the BMW,the similar directions of mantle flow and Paleo-Pacific Plate subduction,and migration of basin depocenters indicate trench-perpendicular mantle flow was a key factor in the formation of the BMW.Moreover,these basaltic rocks have elevatedδ^(66)Zn values(0.22‰to 0.52‰),indicating recycled carbonates have been added into their mantle source,which increased the mantle flow velocity.Combined with slab roll-back in the Late Mesozoic,it created the essential conditions for mantle flow to promote the formation of the eastern Asian BMW.展开更多
The Shatsky Rise ridge-ridge-ridge triple junction is an ancient triple junction in the Western Pacific Ocean whose initial geodynamic process is poorly understood and can only be inferred based on indirect geological...The Shatsky Rise ridge-ridge-ridge triple junction is an ancient triple junction in the Western Pacific Ocean whose initial geodynamic process is poorly understood and can only be inferred based on indirect geological and geophysical constraints.In this paper,we present three-dimensional numerical models that simulate the Shatsky Rise triple junction and calculate its coupled mantle flow and temperature structure.The mantle flow velocity field shows several distinctive features:1)stronger mantle upwelling closer to the ridge axis and triple junction;2)greater upwelling velocity at the faster-spreading ridges;and 3)the most significant increase in upwelling velocity for the slowest-spreading ridge toward the triple junction.The calculated mantle temperature field also reveals distinctive characteristics:1)sharp increases in the mantle temperature with depth and increases toward the spreading ridges and triple junction;2)the faster-spreading ridges are associated with higher temperatures at depth and identical distances from the triple junction;and 3)the slowest-spreading ridge shows the greatest increase in the along-ridge-axis temperature toward the triple junction.Compared to many present-day triple junctions with slower spreading rates,the along-ridge-axis velocity and thermal fields of the Shatsky Rise are more altered due to the presence of the triple junction.展开更多
Based on ophiolite sequences,seismic velocities of rocks and seismic profiles of ocean basins,the oceanic crust-mantle boundary can be defined as the contact between the solid,ductile deformed mantle and the
The mantle unsteady flows, which are in an incompressible and isoviscous spherical shell, are investigated by using algorithms of the parallel Lagrange multiplier dissonant decomposition method (LMDDM) and the paralle...The mantle unsteady flows, which are in an incompressible and isoviscous spherical shell, are investigated by using algorithms of the parallel Lagrange multiplier dissonant decomposition method (LMDDM) and the parallel Lagrange multiplier discontinuous deformation analyses (LMDDA) in this paper. Some physical fields about mantle flows such as velocity, pressure, temperature, stress and the force to the crust of the Asian continent are calculated on a parallel computer.展开更多
Shear wave splitting(SWS)is regarded as the most effective geophysical method to delineate mantle flow fields by detecting seismic azimuthal anisotropy in the earth's upper mantle,especially in tectonically active...Shear wave splitting(SWS)is regarded as the most effective geophysical method to delineate mantle flow fields by detecting seismic azimuthal anisotropy in the earth's upper mantle,especially in tectonically active regions such as subduction zones.The Aleutian-Alaska subduction zone has a convergence rate of approximately 50 mm/yr,with a trench length reaching nearly 2800 km.Such a long subduction zone has led to intensive continental deformation and numerous strong earthquakes in southern and central Alaska,while northern Alaska is relatively inactive.The sharp contrast makes Alaska a favorable locale to investigate the impact of subduction on mantle dynamics.Moreover,the uniqueness of this subduction zone,including the unusual subducting type,varying slab geometry,and atypical magmatic activity and composition,has intrigued the curiosity of many geoscientists.To identify different sources of seismic anisotropy beneath the Alaska region and probe the influence of a geometrically varying subducting slab on mantle dynamics,extensive SWS analyses have been conducted in the past decades.However,the insufficient station and azimuthal coverage,especially in early studies,not only led to some conflicting results but also strongly limited the in-depth investigation of layered anisotropy and the estimation of anisotropy depth.With the completion of the Transportable Array project in Alaska,recent studies have revealed more detailed mantle structures and characteristics based on the dense station coverage and newly collected massive seismic data.In this study,we review significant regional-and continental-scale SWS studies in the Alaska region and conclude the mantle flow fields therein,to understand how a geometrically varying subducting slab alters the regional mantle dynamics.The summarized mantle flow mechanisms are believed to be conducive to the understanding of seismic anisotropy patterns in other subduction zones with a complicated tectonic setting.展开更多
Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes.Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been ...Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes.Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been suggested to explain the space-time distribution of magmatism in east Africa.We devise paleogeographically constrained global models of mantle convection and,based on the evolution of flow in the deepest lower mantle,show that the Afar plume migrated southward throughout its lifetime.The models suggest that the mobile Afar plume provides a dynamically consistent explanation for the spatial extent of the southward propagation of the east African rift system(EARS),which is difficult to explain by the northeastward migration of Africa over one or more fixed plumes alone,over the last≈45 Myr.We further show that the age-progression of volcanism associated with the southward propagation of EARS is consistent with the apparent surface hotspot motion that results from southward motion of the modelled Afar plume beneath the northeastward migrating African plate.The models suggest that the Afar plume became weaker as it migrated southwards,consistent with trends observed in the geochemical record.展开更多
We investigated the relationships among slab geometry, obliquity, and the thermal regime associated with the subduction of oceanic plates using a three-dimensional （3D） parallelepiped thermal convection model. Vario...We investigated the relationships among slab geometry, obliquity, and the thermal regime associated with the subduction of oceanic plates using a three-dimensional （3D） parallelepiped thermal convection model. Various models with convex and concave slab shapes were constructed in the numerical simu- lation, and the temperature and mantle flow distributions were calculated. The results revealed that when the slab dip angle increases, or the obliquity of subduction becomes steeper, the interplate tem- perature decreases remarkably. Cooler （warmer） zones on the plate interface were identified from the modeling where there was a larger （smaller） subduction angle. Consequently, the interplate temperature distribution is partly controlled by the true subduction angle （TSA）, which is a function of the slab dip angle and the obliquity of subduction. The rate of change of the interface temperature for the TSA was 10-50 ℃ （10°〈 TSA 〈 20°） at depths ranging from （TSA 10） × 5 km to 60 ＋ （TSA 10） × 5 km for a fiat slab after a subduction history of 7 Myrs. The along-arc slab curvature affects the variation in TSA. The slab radius also appeared to influence the radius of induced mantle flow.展开更多
Ultra-low velocity zones(ULVZs)provide important information on the composition and dynamics of the core-mantle boundary(CMB).However,their global distribution and characteristics are not well constrained,especially n...Ultra-low velocity zones(ULVZs)provide important information on the composition and dynamics of the core-mantle boundary(CMB).However,their global distribution and characteristics are not well constrained,especially near African large low-shear velocity provinces(LLSVPs).Here,we used ScS precursor(SdS)and postcursor(ScscS)phases recorded by various seismic networks in Africa and South America to investigate the ULVZ characteristics underlying the South Atlantic Ocean.We found no evidence of ULVZs near the SE boundary of South America,but an ULVZ was found within the SW boundary of the African LLSVP,with thicknesses ranging from 11–18 km and reductions in S-wave velocities of 18%–34%.Our results,combined with the global distribution of ULVZs,suggest that thermal activity may be essential to ULVZ formation.Moreover,subducted slab and mantle flow may also play a key role,depending on the location of the ULVZs.展开更多
The Yinggehai Basin is a unique NNW-trending petroliferous basin in the northwestern South China Sea.This paper mainly utilized stratigraphic,tectonic and seismic data by characterizing the geological structures and c...The Yinggehai Basin is a unique NNW-trending petroliferous basin in the northwestern South China Sea.This paper mainly utilized stratigraphic,tectonic and seismic data by characterizing the geological structures and conducting the geo-mechanical analysis to study the formation,evolution and dynamics of the Yinggehai Basin.The study indicates that the Ailaoshan-Truong Son extruded terrane is composed of multiple secondary extruded bodies.The Red River fault zone,located within the Qiangtang-Simao-Yinggehai mantle flow channel and basin zone,experienced transform-type sinistral strike-slip motion before the basin forming stage and formed a NW-trending extruded mantle uplift,which activated the Yinggehai basin.After experiencing the rift depression,fault depression,and fault subsidence,the basin eventually formed large-scale,thick sedimentation features with ideal hydrocarbon-forming conditions at the end of the Miocene.Later,the basin dynamically transformed and entered a period of tectonic superposition,reworking,and thermal subsidence.Superposition of the NNW thrust sinistral strike-slip fault zone on the northern Hanoi sub-basin complicated the basin structure.Since the Pliocene,the southern Yinggehai main basin has been transformed into an extensional dextral strike-slip environment that hosted numerous mud diapirs.The thin crust and high geothermal gradient provide favorable conditions for the large-scale accumulation of natural gas.展开更多
A huge triangle-shaped tectonic region in eastern Asia plays host to numerous major earth- quakes. The three boundaries of this region, which contains plateaus, mountains, and intermountain basins, are roughly the Him...A huge triangle-shaped tectonic region in eastern Asia plays host to numerous major earth- quakes. The three boundaries of this region, which contains plateaus, mountains, and intermountain basins, are roughly the Himalayan arc, the Tianshan-Baikal, and longitude line -105°E. Within this trian- gular region, tectonism is intense and major deformation occurs both between crustal blocks and within most of them. Outside of this region, rigid blocks move as a whole with relatively few major earthquakes and relatively weak Cenozoic deformation. On a large tectonic scale, the presence of this broad region of intraplate deformation results from dynamic interactions between the Indian, Philippine Sea-West Pacific, and Eurasian plates, as well as the influence of deep-level mantle flow. The Indian subcontinent, which continues to move northwards at -40 mm/a since its collision with Eurasia, has plunged beneath Tibet, resulting in various movements and deformations along the Himalayan arc that diffuse over a long distance into the hinterland of Asia. The northward crustal escape of Asia from the Himalayan collisional zone turns eastwards and southeastwards along 95°-100°E longitude and defines the eastern Himalayan syntaxis. At the western Himalayan syntaxis, the Pamirs continue to move into central Asia, leading to crustal deformation and earthquakes that are largely accommodated by old EW or NW trending faults in the bordering areas between China, Mongolia, and Russia, and are restricted by the stable landmass northwest of the Tianshan-Altai-Baikal region. The subduction of the Philippine and Pacific plates under the Eurasian continent has generated a very long and narrow seismic zone along trenches and island arcs in the marginal seas while imposing only slight horizontal compression on the Asian continent that does not impede the eastward motion of eastern Asia. In the third dimension, there may be southeastward deep mantle flow beneath most of Eurasia that reaches the marginal seas and may contribute to extension along the eastern margin of Eurasia.展开更多
In this paper, mantle circulation flow, continental drift, earthquake origin and other mechanical principles are examined as they apply to earthquake engineering, seismology and dynamics of fluid saturated porous medi...In this paper, mantle circulation flow, continental drift, earthquake origin and other mechanical principles are examined as they apply to earthquake engineering, seismology and dynamics of fluid saturated porous medium. The relationship of mantle flow to earthquakes is examined and clarified, and a new model, different from Haskell’s, is proposed for the earthquake mechanism. The proposed new model is based on the discovery that two pairs of jump stress and jump velocity will start to act from the fault plane. Records obtained directly from recent earthquakes nearby and right on the fault break show a very large velocity impulse, which verify, indirectly, the new mechanism proposed by the author. Further, at least two physical parameters that characterize the seismic intensity must be specified, because according to the discontinuous (jump) wave theory, at the earthquake source, the stress jump and the velocity jump of particle motion should act simultaneously when a sudden break occurs. The third key parameter is shown to be the break (fracture) propagation speed together with the break plane area. This parameter influences the form of the unloading time function at the source. The maximum seismic stress in and displacement of a building are estimated for two unfavorable combinations of the building and its base ground in terms of their relative rigidity. Finally, it is shown that Biot’s theory of wave propagation in fluid saturated porous media is valid only when fluid flow cannot occur.展开更多
基金financially supported by the National Key R&D Program of China(No.2022YFF0801002)the National Natural Science Foundation of China(No.42372065)the Natural Science Foundation of Jilin Province(No.20220101178JC)。
文摘The Paleo-Pacific Plate stagnated in the mantle transition zone beneath northeast Asia during the Late Mesozoic,resulting in the eastern Asian big mantle wedge(BMW).However,its formation mechanism remains unclear.Here,we analyzed elemental and isotopic compositions of 126-60 Ma intraplate basaltic rocks to map the mantle flow pattern and investigate the implications for the formation of the BMW.These rocks exhibit eastward an increase in Ba/Nb,Ba/La,^(87)Sr/^(86)Sr,and^(208)Pb/^(204)Pb ratios,while a decrease in Nb/Yb,Zr/Yb,Ta/Yb,and Nb/Nb*ratios,indicating mixing between the fertile mantle and the depleted mantle modified by slab material,implying the occurrence of trench-perpendicular mantle flow.The coeval mantle flow and formation of the BMW,the similar directions of mantle flow and Paleo-Pacific Plate subduction,and migration of basin depocenters indicate trench-perpendicular mantle flow was a key factor in the formation of the BMW.Moreover,these basaltic rocks have elevatedδ^(66)Zn values(0.22‰to 0.52‰),indicating recycled carbonates have been added into their mantle source,which increased the mantle flow velocity.Combined with slab roll-back in the Late Mesozoic,it created the essential conditions for mantle flow to promote the formation of the eastern Asian BMW.
基金This research was supported by the National Key R&D Program of China(No.2018YFC0309800)the China Ocean Mineral Resources R&D Association(No.DY135S2-1-04)+4 种基金the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD 0205)the Guangdong Basic and Applied Basic Research Foundation(Nos.2021B1515020098 and 2021A1515012227)the National Natural Science Foundation of China(Nos.41776058,41890813,41976066,91858207 and 41806067)the Chinese Academy of Sciences(Nos.ISEE2019ZR01,QYZDY-SSW-DQC005,133244KYSB20180029,131551KYSB20200021,Y4SL021001,and XDB41000000)the China National Space Administration(No.D020303).
文摘The Shatsky Rise ridge-ridge-ridge triple junction is an ancient triple junction in the Western Pacific Ocean whose initial geodynamic process is poorly understood and can only be inferred based on indirect geological and geophysical constraints.In this paper,we present three-dimensional numerical models that simulate the Shatsky Rise triple junction and calculate its coupled mantle flow and temperature structure.The mantle flow velocity field shows several distinctive features:1)stronger mantle upwelling closer to the ridge axis and triple junction;2)greater upwelling velocity at the faster-spreading ridges;and 3)the most significant increase in upwelling velocity for the slowest-spreading ridge toward the triple junction.The calculated mantle temperature field also reveals distinctive characteristics:1)sharp increases in the mantle temperature with depth and increases toward the spreading ridges and triple junction;2)the faster-spreading ridges are associated with higher temperatures at depth and identical distances from the triple junction;and 3)the slowest-spreading ridge shows the greatest increase in the along-ridge-axis temperature toward the triple junction.Compared to many present-day triple junctions with slower spreading rates,the along-ridge-axis velocity and thermal fields of the Shatsky Rise are more altered due to the presence of the triple junction.
文摘Based on ophiolite sequences,seismic velocities of rocks and seismic profiles of ocean basins,the oceanic crust-mantle boundary can be defined as the contact between the solid,ductile deformed mantle and the
基金State Climbing Project (95-S-05-02) and State Natural Science Foundation of China (49724232).
文摘The mantle unsteady flows, which are in an incompressible and isoviscous spherical shell, are investigated by using algorithms of the parallel Lagrange multiplier dissonant decomposition method (LMDDM) and the parallel Lagrange multiplier discontinuous deformation analyses (LMDDA) in this paper. Some physical fields about mantle flows such as velocity, pressure, temperature, stress and the force to the crust of the Asian continent are calculated on a parallel computer.
基金supported by the Outstanding Youth Project of Natural Science Foundation of Heilongjiang(YQ2023D006).
文摘Shear wave splitting(SWS)is regarded as the most effective geophysical method to delineate mantle flow fields by detecting seismic azimuthal anisotropy in the earth's upper mantle,especially in tectonically active regions such as subduction zones.The Aleutian-Alaska subduction zone has a convergence rate of approximately 50 mm/yr,with a trench length reaching nearly 2800 km.Such a long subduction zone has led to intensive continental deformation and numerous strong earthquakes in southern and central Alaska,while northern Alaska is relatively inactive.The sharp contrast makes Alaska a favorable locale to investigate the impact of subduction on mantle dynamics.Moreover,the uniqueness of this subduction zone,including the unusual subducting type,varying slab geometry,and atypical magmatic activity and composition,has intrigued the curiosity of many geoscientists.To identify different sources of seismic anisotropy beneath the Alaska region and probe the influence of a geometrically varying subducting slab on mantle dynamics,extensive SWS analyses have been conducted in the past decades.However,the insufficient station and azimuthal coverage,especially in early studies,not only led to some conflicting results but also strongly limited the in-depth investigation of layered anisotropy and the estimation of anisotropy depth.With the completion of the Transportable Array project in Alaska,recent studies have revealed more detailed mantle structures and characteristics based on the dense station coverage and newly collected massive seismic data.In this study,we review significant regional-and continental-scale SWS studies in the Alaska region and conclude the mantle flow fields therein,to understand how a geometrically varying subducting slab alters the regional mantle dynamics.The summarized mantle flow mechanisms are believed to be conducive to the understanding of seismic anisotropy patterns in other subduction zones with a complicated tectonic setting.
基金supported by ARC grants IH130200012 and DP130101946supported by the National Science Foundation under award EAR-1645775undertaken with the assistance of resources from the National Computational Infrastructure(NCI),which is supported by the Australian Government。
文摘Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes.Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been suggested to explain the space-time distribution of magmatism in east Africa.We devise paleogeographically constrained global models of mantle convection and,based on the evolution of flow in the deepest lower mantle,show that the Afar plume migrated southward throughout its lifetime.The models suggest that the mobile Afar plume provides a dynamically consistent explanation for the spatial extent of the southward propagation of the east African rift system(EARS),which is difficult to explain by the northeastward migration of Africa over one or more fixed plumes alone,over the last≈45 Myr.We further show that the age-progression of volcanism associated with the southward propagation of EARS is consistent with the apparent surface hotspot motion that results from southward motion of the modelled Afar plume beneath the northeastward migrating African plate.The models suggest that the Afar plume became weaker as it migrated southwards,consistent with trends observed in the geochemical record.
文摘We investigated the relationships among slab geometry, obliquity, and the thermal regime associated with the subduction of oceanic plates using a three-dimensional （3D） parallelepiped thermal convection model. Various models with convex and concave slab shapes were constructed in the numerical simu- lation, and the temperature and mantle flow distributions were calculated. The results revealed that when the slab dip angle increases, or the obliquity of subduction becomes steeper, the interplate tem- perature decreases remarkably. Cooler （warmer） zones on the plate interface were identified from the modeling where there was a larger （smaller） subduction angle. Consequently, the interplate temperature distribution is partly controlled by the true subduction angle （TSA）, which is a function of the slab dip angle and the obliquity of subduction. The rate of change of the interface temperature for the TSA was 10-50 ℃ （10°〈 TSA 〈 20°） at depths ranging from （TSA 10） × 5 km to 60 ＋ （TSA 10） × 5 km for a fiat slab after a subduction history of 7 Myrs. The along-arc slab curvature affects the variation in TSA. The slab radius also appeared to influence the radius of induced mantle flow.
基金supported by the National Natural Science Foundation of China(Nos.41774053 and 42074059)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(No.XDB42000000).
文摘Ultra-low velocity zones(ULVZs)provide important information on the composition and dynamics of the core-mantle boundary(CMB).However,their global distribution and characteristics are not well constrained,especially near African large low-shear velocity provinces(LLSVPs).Here,we used ScS precursor(SdS)and postcursor(ScscS)phases recorded by various seismic networks in Africa and South America to investigate the ULVZ characteristics underlying the South Atlantic Ocean.We found no evidence of ULVZs near the SE boundary of South America,but an ULVZ was found within the SW boundary of the African LLSVP,with thicknesses ranging from 11–18 km and reductions in S-wave velocities of 18%–34%.Our results,combined with the global distribution of ULVZs,suggest that thermal activity may be essential to ULVZ formation.Moreover,subducted slab and mantle flow may also play a key role,depending on the location of the ULVZs.
基金the CNOOC Zhanjiang Branch Research Institute for providing the data and funding(No.CCL2019ZJFNO734).
文摘The Yinggehai Basin is a unique NNW-trending petroliferous basin in the northwestern South China Sea.This paper mainly utilized stratigraphic,tectonic and seismic data by characterizing the geological structures and conducting the geo-mechanical analysis to study the formation,evolution and dynamics of the Yinggehai Basin.The study indicates that the Ailaoshan-Truong Son extruded terrane is composed of multiple secondary extruded bodies.The Red River fault zone,located within the Qiangtang-Simao-Yinggehai mantle flow channel and basin zone,experienced transform-type sinistral strike-slip motion before the basin forming stage and formed a NW-trending extruded mantle uplift,which activated the Yinggehai basin.After experiencing the rift depression,fault depression,and fault subsidence,the basin eventually formed large-scale,thick sedimentation features with ideal hydrocarbon-forming conditions at the end of the Miocene.Later,the basin dynamically transformed and entered a period of tectonic superposition,reworking,and thermal subsidence.Superposition of the NNW thrust sinistral strike-slip fault zone on the northern Hanoi sub-basin complicated the basin structure.Since the Pliocene,the southern Yinggehai main basin has been transformed into an extensional dextral strike-slip environment that hosted numerous mud diapirs.The thin crust and high geothermal gradient provide favorable conditions for the large-scale accumulation of natural gas.
基金supported by the National Development Program of Major Basic Research(973 Program)(2008CB425703)
文摘A huge triangle-shaped tectonic region in eastern Asia plays host to numerous major earth- quakes. The three boundaries of this region, which contains plateaus, mountains, and intermountain basins, are roughly the Himalayan arc, the Tianshan-Baikal, and longitude line -105°E. Within this trian- gular region, tectonism is intense and major deformation occurs both between crustal blocks and within most of them. Outside of this region, rigid blocks move as a whole with relatively few major earthquakes and relatively weak Cenozoic deformation. On a large tectonic scale, the presence of this broad region of intraplate deformation results from dynamic interactions between the Indian, Philippine Sea-West Pacific, and Eurasian plates, as well as the influence of deep-level mantle flow. The Indian subcontinent, which continues to move northwards at -40 mm/a since its collision with Eurasia, has plunged beneath Tibet, resulting in various movements and deformations along the Himalayan arc that diffuse over a long distance into the hinterland of Asia. The northward crustal escape of Asia from the Himalayan collisional zone turns eastwards and southeastwards along 95°-100°E longitude and defines the eastern Himalayan syntaxis. At the western Himalayan syntaxis, the Pamirs continue to move into central Asia, leading to crustal deformation and earthquakes that are largely accommodated by old EW or NW trending faults in the bordering areas between China, Mongolia, and Russia, and are restricted by the stable landmass northwest of the Tianshan-Altai-Baikal region. The subduction of the Philippine and Pacific plates under the Eurasian continent has generated a very long and narrow seismic zone along trenches and island arcs in the marginal seas while imposing only slight horizontal compression on the Asian continent that does not impede the eastward motion of eastern Asia. In the third dimension, there may be southeastward deep mantle flow beneath most of Eurasia that reaches the marginal seas and may contribute to extension along the eastern margin of Eurasia.
文摘In this paper, mantle circulation flow, continental drift, earthquake origin and other mechanical principles are examined as they apply to earthquake engineering, seismology and dynamics of fluid saturated porous medium. The relationship of mantle flow to earthquakes is examined and clarified, and a new model, different from Haskell’s, is proposed for the earthquake mechanism. The proposed new model is based on the discovery that two pairs of jump stress and jump velocity will start to act from the fault plane. Records obtained directly from recent earthquakes nearby and right on the fault break show a very large velocity impulse, which verify, indirectly, the new mechanism proposed by the author. Further, at least two physical parameters that characterize the seismic intensity must be specified, because according to the discontinuous (jump) wave theory, at the earthquake source, the stress jump and the velocity jump of particle motion should act simultaneously when a sudden break occurs. The third key parameter is shown to be the break (fracture) propagation speed together with the break plane area. This parameter influences the form of the unloading time function at the source. The maximum seismic stress in and displacement of a building are estimated for two unfavorable combinations of the building and its base ground in terms of their relative rigidity. Finally, it is shown that Biot’s theory of wave propagation in fluid saturated porous media is valid only when fluid flow cannot occur.
