The western China lies in the convergence zone between Eurasian and Indian plates.It is an ideal place to study the lithosphere dynamics and tectonic evolutions on the continental Earth.The lithospheric strength is a ...The western China lies in the convergence zone between Eurasian and Indian plates.It is an ideal place to study the lithosphere dynamics and tectonic evolutions on the continental Earth.The lithospheric strength is a key factor in controlling the lithosphere dynamics and deformations.The effective elastic thickness(T_(e))of the lithosphere can be used to address the lithospheric strength.Previous researchers only used one of the admittance or coherence methods to investigate the T_(e) in the western China.Moreover,most of them ignored the internal loads of the lithosphere during the T_(e) calculation,which can produce large biases in the T_(e) estimations.To provide more reliable T_(e) estimations,we used a new joint inversion method that integrated both admittance and coherence techniques to compute the T_(e) in this study,with the WGM2012 gravity data,the ETOPO1 topographic data,and the Moho depths from the CRUST1.0 model.The internal loads are considered and investigated using the load ratio(F).Our results show that the joint inversion method can yield reliable T_(e) and F values.Based on the analysis of T_(e) and F distributions,we suggest(1)the northern Tibetan Plateau could be the front edge of the plate collision of Eurasian and Indian plates;(2)the southern and part of central Tibetan Plateau have a strong lithospheric mantle related to the rigid underthrusting Indian plate;(3)the southeastern Tibetan Plateau may be experiencing the delamination of lithosphere and upwelling of asthenosphere.展开更多
To understand the rheology,structure,and tectonics of the lithosphere in the Mariana subduction zone and surrounding regions,we calculated the effective elastic thickness of the lithosphere(Te)in these areas using the...To understand the rheology,structure,and tectonics of the lithosphere in the Mariana subduction zone and surrounding regions,we calculated the effective elastic thickness of the lithosphere(Te)in these areas using the improved moving window admittance technique(MWAT)method.We find that smaller data grid spacing can better reflect Te variations in the subduction zone.The Te of the study region ranges from 0 to 47 km.The Te is reduced from 40 km on the seaward side of the outer-rise region to 1-2 km along the trench axis.The lithospheric breaking distance from the trench axis ranges from 0 to 250 km.We suggest that the intermediate Te values in seamounts and high Te values on the seaward side of the outer-rise region respectively reflect the‘fossil’rheological state and current lithospheric strength of the Pacific plate.The faulting induced by the downward bending of subducting plate not only ruptures the lithosphere but also contributes to the mantle serpentinization,significantly reducing the lithospheric strength.The largest breaking distance of the Ogasawara Plateau may be due to the increase in the mass load of the subducting plate in the Ogasawara Plateau and the significant horizontal bending force in the plate caused by the resistance of seamounts to subduction.Furthermore,a good positive correlation exists between the breaking distance and subduction dip angle along the trench axis.We suggest that the subducting plate with a larger breaking distance is likely to form a larger subduction angle.展开更多
The elastic thickness of the lithosphere(Te)is a key parameter used to describe the strength of the lithosphere.It is usually estimated by a spectral analysis between gravity and topography.In previous research on the...The elastic thickness of the lithosphere(Te)is a key parameter used to describe the strength of the lithosphere.It is usually estimated by a spectral analysis between gravity and topography.In previous research on the estimation of Te,altimetry data were used on both the gravity data and topography data,which could lead to deviations.The study described in this paper analyzed the effects of using gravity anomalies derived from different data sources on the estimation of Te,Taking the western Pacific region as an example,this study analyzed the impact of the repeated presence of altimetry satellite data on the calculation of the effective elastic thickness and found that if gravity anomalies and topography model both contain altimetry satellite data,they systematically overestimate effective elasticity.For a uniform area,the difference in Te can reach up to 30%.For a Te distribution,the difference can reach up to about16%.After eliminating this effect,the effective elastic thickness of the western Pacific region was found to be 10 km,and the statistical results of the effective elastic thickness distribution showed that the effective elastic thickness of the lithosphere in most areas of the western Pacific is about 12 km.The paper shows the importance of choosing the appropriate gravity model in evaluating the elastic thickness of lithosphere in the oceans.A figure of Te at seamounts with loading ages demonstrates that Te in the western Pacific is generally distributed within the 100-300℃isotherm depth and does not increase with loading age.展开更多
The effective lithospheric elastic thickness of the continent is an important parameter for examination of the large-scale structure and analyses of the mechanism of isostatic compensation within the plate, and a para...The effective lithospheric elastic thickness of the continent is an important parameter for examination of the large-scale structure and analyses of the mechanism of isostatic compensation within the plate, and a parameter standing for the strength of the lithosphere. The Te values along Quanzhou-Heishui, the southeast section of the Arctic Ocean-Eurasian Continent-Pacific Ocean geoscience transect, are estimated by using the coherence technique developed by Forsyth. Studies of the feature of the coherence between gravity and topography suggest that at short wavelengths (6. 6-100 km) for each data box that is used to estimate Te, the plate is strong enough to support topographic loads and gravity and topography are uncorrelated. At long wavelengths where the plate is deflected by surface and subsurface loads are compensated by the flexure model. Sichuan land-stone with low heat-flow values has high Te values whereas in Ninghua, Datian, land-stone with high heat-flow values has low Te values, which reflects a correlation, low heat-flow values corresponding to high Te values and high heat-flow values corresponding to low Te values. Te values can be divided into two sections: northwest high section and southeast low section. There is roughly a positive correlation between crustal thickness and effective elastic thickness of the lithosphere.展开更多
On February 6, 2023, the doublet earthquake including two main shocks with magnitudes M_(W)7.8 and M_(W)7.5, occurred near the western side of the East Anatolian Fault at the southeast boundary of the Anatolian Platea...On February 6, 2023, the doublet earthquake including two main shocks with magnitudes M_(W)7.8 and M_(W)7.5, occurred near the western side of the East Anatolian Fault at the southeast boundary of the Anatolian Plateau in Turkey. Based on the WGM2012 Bouguer gravity anomaly data and the Etopo1topography data, this study first introduced a joint inversion of admittance and coherence functions and used the Bayesian optimal parameter estimation method to obtain the effective elastic thickness Teand loading ratio F of the lithosphere for various tectonic units in the Anatolian Plateau. Secondly, we discussed the characteristics and influencing factors of the lithospheric mechanical strength and analyzed its relationship with seismic activity. The lithospheric mechanical strength of the Anatolian Plateau showed clear lateral heterogeneity and a "weak-strong-weak" spatial pattern from east to west,reflecting various tectonic processes. At last, the strong seismic activity was found where the lithospheric strength was low in the Anatolian Plate. We also incorporated GPS strain rate and other results to investigate the tectonic background and primary causes of the M_(W)7.8 and M_(W)7.5 doublet earthquakes in Turkey. The results have a good insight into urban safety design in the Turkish region, including postdisaster rehabilitation, earthquake hazard assessment, and loss reduction.展开更多
The effective elastic thickness (Te) represents the thickness of the elastic layer or the flexural rigidity of the lithosphere, the equivalent of which can be calculated from the spectral analysis of gravity and top...The effective elastic thickness (Te) represents the thickness of the elastic layer or the flexural rigidity of the lithosphere, the equivalent of which can be calculated from the spectral analysis of gravity and topographic data. Studies of Te have profound influence on intracontinental deformation, and coupling of the tectonic blocks. In this paper, we use the multitaper spectral estimation method to calculate the coherence between Bouguer gravity and topography data, and to obtain the Te map of South China. Through the process of correction, we discuss the relationships of Te versus heat flow, and Te versus seismicity. The results show that Te distribution of South China is affected by three factors:the original age, which controls the basic feature;the Mesozoic evolution, which affects the Te distribution;and the neotectonic movement, which shaped the final distribution. The crust age has a positive correlation with the first-order Te distribution;thus the Yangtze Craton has a relatively higher Te (about 50 km) whereas the Te in Cathaysia block is only 10e20 km. By analysis and comparison among the tectonic models of South China, the Te distribution can be well explained using the flat-subduction model. As is typical with neotectonics, the region with a higher heat flow is related with a lower Te. The seismicity does not have a clear relationship with Te, but the strong seismicity could cause a low Te. Seismogenic layer (Ts) has a similar trend as Te in the craton, whereas in other areas the relationship is complex.展开更多
Using bathymetry and altimetric gravity anomalies, a 1°×9 1° lithospheric effective elastic thickness(Te) model over the Louisville Ridge and its adjacent regions is calculated using the moving window...Using bathymetry and altimetric gravity anomalies, a 1°×9 1° lithospheric effective elastic thickness(Te) model over the Louisville Ridge and its adjacent regions is calculated using the moving window admittance technique. For comparison, three bathymetry models are used: general bathymetric charts of the oceans, SIO V15.1,and BAT_VGG. The results show that BAT_VGG is more suitable for calculating T e than the other two models. T e along the Louisville Ridge was re-evaluated. The southeast of the ridge has a medium Te of 10–20 km, while Te increases dramatically seaward of the Tonga-Kermadec trench as a result of the collision of the Pacific and IndoAustralian plates.展开更多
We conducted a detailed analysis of along-trench variations in the flexural bending of the subducting Pacific Plate at the Tonga-Kermadec Trench.Inversions were conducted to obtain best-fitting solutions of trench-axi...We conducted a detailed analysis of along-trench variations in the flexural bending of the subducting Pacific Plate at the Tonga-Kermadec Trench.Inversions were conducted to obtain best-fitting solutions of trench-axis loadings and variations in the effective elastic plate thickness for the analyzed flexural bending profiles.Results of the analyses revealed significant along-trench variations in plate flexural bending:the trench relief(W0)of 1.9 to 5.1 km;trench-axis vertical loading(V0)of-0.5×10^12 to 2.2×10^12 N/m;axial bending moment(M0)of 0.1×10^17 to 2.2×10^17 N;effective elastic plate thickness seaward of the outer-rise region(Te^M)of 20 to 65 km,trench-ward of the outer-rise(Te^M)of 11 to 33 km,and the transition distance(Xr)of 20 to 95 km.The Horizon Deep,the second greatest trench depth in the world,has the greatest trench relief(W0 of 5.1km)and trench-axis loading(V0 of 2.2×10^12N/m);these values are only slightly smaller than that of the Challenger Deep(W0 of 5.7km and V0 of 2.9×10^12N/m)and similar to that of the Sirena Deep(W0 of 5.2 km and V0 of 2.0×10^12 N/m)of the Mariana Trench,suggesting that these deeps are linked to great flexural bending of the subducting plates.Analyses using three independent methods,i.e.,the/inversion,the flexural curvature/yield strength envelope analysis,and the elasto-plastic bending model with normal faults,all yielded similar average Te reduction of 28%-36% and average Te reduction area S△Te of 1195-1402 km^2 near the trench axis.The calculated brittle yield zone depth from the flexural curvature/yield strength envelope analysis is also consistent with the distribution of the observed normal faulting earthquakes.Comparisons of the Manila,Philippine,Tonga-Kermadec,Japan,and Mariana Trenches revealed that the average values Te^M of Te^M and both in general increase with the subducting plate age.展开更多
On the basis of more than 900 heat flow data in China and the surrounding seas, the authors study the geothermal characteristics of major tectonic units in China. The spatial pattern of heat flow and other thermal pa...On the basis of more than 900 heat flow data in China and the surrounding seas, the authors study the geothermal characteristics of major tectonic units in China. The spatial pattern of heat flow and other thermal parameters for lithosphere exhibit significant lateral variation, originating from the Cenozoic tectonothermal activities related to the subduction of the Pacific plate and the collision between India and Asia. The mechanical strength of the crust and the seismicity of tectonic units were strongly affected by geothermal characteristics of units. The crustal heat production rate also shows the lateral heterogeneity, implying the significant lateral variation of bulk composition of the crust in China.展开更多
Recent experiments revealed many new phenomena of the macroscopic domain patterns in the stress-induced phase transformation of a superelastic polycrystalline NiTi tube during tensile loading. The new phenomena includ...Recent experiments revealed many new phenomena of the macroscopic domain patterns in the stress-induced phase transformation of a superelastic polycrystalline NiTi tube during tensile loading. The new phenomena include deformation instability with the formation of a helical domain, domain topology transition from helix to cylinder, domain-front branching and loading-path dependence of domain patterns. In this paper, we model the polycrystal as an elastic continuum with nonconvex strain energy and adopt the non-local strain gradient energy to account for the energy of the diffusive domain front. We simulate the equilibrium domain patterns and their evolution in the tubes under tensile loading by a non-local Finite Element Method (FEM). It is revealed that the observed loading-path dependence and topology transition of do- main patterns are due to the thermodynamic metastability of the tube system. The computation also shows that the tube-wall thickness has a significant effect on the domain patterns: with fixed material properties and interfacial energy density, a large tube-wall thickness leads to a long and slim helical domain and a severe branching of the cylindrical-domain front.展开更多
Jiyang Depression, located in the southeast Bohai Bay Basin, has the geomorpho-logic framework of multiple uplifts intervening with sags. Combined the abundant geo-temperature data and thermo-physical parameters of ro...Jiyang Depression, located in the southeast Bohai Bay Basin, has the geomorpho-logic framework of multiple uplifts intervening with sags. Combined the abundant geo-temperature data and thermo-physical parameters of rock samples derived from oil and gas exploration during the past years, with geothermal approaches, here we investigate the litho-spheric thermal regime of this depression. Consequently, based on the obtained thermal struc-ture of the lithosphere, along with rheological modeling, the lithospheric rheological profiles of Jiyang Depression are then determined. Our results show that the temperature at the bottom of sedimentary cover within depression varies from 129℃ to 298 ℃ , accompanied with the base-ment heat flow ranging between 54.3 and 60.5 mW/m2; and 406℃-436℃ for temperature at the bottom of the upper crust, along with heat flow varying from 47.7 to 52.6 mW/m2; while the tem-perature at the bottom of the middle crust is between 537 ℃ and 572 ℃, as well as heat flow ranging from 41.3 to 56.3 mW/m2. The temperature at Moho ranges from 669 ℃ to 721 ℃, the heat flow derived from mantle is between 38.1 and 43.1 mW/m2, and calculated thickness of the thermal lithosphere beneath depression varies from 71 to 90 km. Lithospheric thermal regime is a close correlation with such factors as crustal thickness and surface heat flow, etc. Usually, the larger the surface heat flow, the larger the deep temperature and heat flow within lithosphere, and the thinner the thermal lithospheric thickness. This high thermal regime of the lithosphere in Jiyang Depression is thought to be related to Cenozoic back-arc spreading during the western Pacific plate subduction into Eurasian continent. Lithospheric rheological modeling shows that the lithosphere in Jiyang Depression is characterized by its distinct rheological stratification as follows: The upper and most part of the middle crust are of brittle, while the lower crust and the lower part of middle crust are all ductile, and lithospheric mantle is dominated by the ductile layer. Additionally, lateral rheological heterogeneities exist in the depression, and the lithospheric strength of sags within depression differs much from each other. The total lithospheric strength of Jiyang Depression is between 1.52 and 2.16×1012 N/m, effective elastic thickness (Te) of the lithosphere in Jiyang Depression is about 24 km, approximating to the thickness of mechanically strong crust (MSC). We suggested that the dehydration of minerals in the subducting zone, along with upwelling of hot materials in the mantle wedge during subduction and back-arc spreading, results in the partial melting at the bottom of curst, which triggers magma intrusion and under-plating. This geodynamics process maybe is the reason for the reduction of lower crustal viscos-ity for ductile flow. Lithospheric rheological stratification controlling the differential deformation styles of brittle fracture or frictional slide in the upper crust and ductile flow in the middle and lower crust, accounts for the basin formation and evolution of Jiyang Depression during Ceno-zoic.展开更多
基金This work is supported by the Special Fund of the Institute of GeophysicsChina Earthquake Administration(No.DQJB20K31)+2 种基金the National Key R&D Program of China(Nos.2018YFC0603502 and2017YFC1500503)the National Natural Science Foundation of China(Nos.41774090 and U1939205)financial support by China Postdoctoral Science Foundation(No.2018M641424)。
文摘The western China lies in the convergence zone between Eurasian and Indian plates.It is an ideal place to study the lithosphere dynamics and tectonic evolutions on the continental Earth.The lithospheric strength is a key factor in controlling the lithosphere dynamics and deformations.The effective elastic thickness(T_(e))of the lithosphere can be used to address the lithospheric strength.Previous researchers only used one of the admittance or coherence methods to investigate the T_(e) in the western China.Moreover,most of them ignored the internal loads of the lithosphere during the T_(e) calculation,which can produce large biases in the T_(e) estimations.To provide more reliable T_(e) estimations,we used a new joint inversion method that integrated both admittance and coherence techniques to compute the T_(e) in this study,with the WGM2012 gravity data,the ETOPO1 topographic data,and the Moho depths from the CRUST1.0 model.The internal loads are considered and investigated using the load ratio(F).Our results show that the joint inversion method can yield reliable T_(e) and F values.Based on the analysis of T_(e) and F distributions,we suggest(1)the northern Tibetan Plateau could be the front edge of the plate collision of Eurasian and Indian plates;(2)the southern and part of central Tibetan Plateau have a strong lithospheric mantle related to the rigid underthrusting Indian plate;(3)the southeastern Tibetan Plateau may be experiencing the delamination of lithosphere and upwelling of asthenosphere.
基金This research was supported by the National Natural Science Foundation of China(Nos.41676039 and 4207061006)the Shandong Young Teacher Growth Program.
文摘To understand the rheology,structure,and tectonics of the lithosphere in the Mariana subduction zone and surrounding regions,we calculated the effective elastic thickness of the lithosphere(Te)in these areas using the improved moving window admittance technique(MWAT)method.We find that smaller data grid spacing can better reflect Te variations in the subduction zone.The Te of the study region ranges from 0 to 47 km.The Te is reduced from 40 km on the seaward side of the outer-rise region to 1-2 km along the trench axis.The lithospheric breaking distance from the trench axis ranges from 0 to 250 km.We suggest that the intermediate Te values in seamounts and high Te values on the seaward side of the outer-rise region respectively reflect the‘fossil’rheological state and current lithospheric strength of the Pacific plate.The faulting induced by the downward bending of subducting plate not only ruptures the lithosphere but also contributes to the mantle serpentinization,significantly reducing the lithospheric strength.The largest breaking distance of the Ogasawara Plateau may be due to the increase in the mass load of the subducting plate in the Ogasawara Plateau and the significant horizontal bending force in the plate caused by the resistance of seamounts to subduction.Furthermore,a good positive correlation exists between the breaking distance and subduction dip angle along the trench axis.We suggest that the subducting plate with a larger breaking distance is likely to form a larger subduction angle.
基金funded by Guangdong Province Introduced Innovative R&D Team of Geological Processes and Natural Disasters around the South China Sea,China(No.2016ZT06N331)the National key Research and Development Program of China,China(No.2017YFC1500101)Guangdong Province Natural Science Foundation,China(No.2018A030310314)。
文摘The elastic thickness of the lithosphere(Te)is a key parameter used to describe the strength of the lithosphere.It is usually estimated by a spectral analysis between gravity and topography.In previous research on the estimation of Te,altimetry data were used on both the gravity data and topography data,which could lead to deviations.The study described in this paper analyzed the effects of using gravity anomalies derived from different data sources on the estimation of Te,Taking the western Pacific region as an example,this study analyzed the impact of the repeated presence of altimetry satellite data on the calculation of the effective elastic thickness and found that if gravity anomalies and topography model both contain altimetry satellite data,they systematically overestimate effective elasticity.For a uniform area,the difference in Te can reach up to 30%.For a Te distribution,the difference can reach up to about16%.After eliminating this effect,the effective elastic thickness of the western Pacific region was found to be 10 km,and the statistical results of the effective elastic thickness distribution showed that the effective elastic thickness of the lithosphere in most areas of the western Pacific is about 12 km.The paper shows the importance of choosing the appropriate gravity model in evaluating the elastic thickness of lithosphere in the oceans.A figure of Te at seamounts with loading ages demonstrates that Te in the western Pacific is generally distributed within the 100-300℃isotherm depth and does not increase with loading age.
基金This paper is supported by GEMOC National Key Center, Macquarie University, Australin.
文摘The effective lithospheric elastic thickness of the continent is an important parameter for examination of the large-scale structure and analyses of the mechanism of isostatic compensation within the plate, and a parameter standing for the strength of the lithosphere. The Te values along Quanzhou-Heishui, the southeast section of the Arctic Ocean-Eurasian Continent-Pacific Ocean geoscience transect, are estimated by using the coherence technique developed by Forsyth. Studies of the feature of the coherence between gravity and topography suggest that at short wavelengths (6. 6-100 km) for each data box that is used to estimate Te, the plate is strong enough to support topographic loads and gravity and topography are uncorrelated. At long wavelengths where the plate is deflected by surface and subsurface loads are compensated by the flexure model. Sichuan land-stone with low heat-flow values has high Te values whereas in Ninghua, Datian, land-stone with high heat-flow values has low Te values, which reflects a correlation, low heat-flow values corresponding to high Te values and high heat-flow values corresponding to low Te values. Te values can be divided into two sections: northwest high section and southeast low section. There is roughly a positive correlation between crustal thickness and effective elastic thickness of the lithosphere.
基金funded by the National Natural Science Foundation of China (Grant Nos.U1939205,41974095)the Basic Research Fund of the Institute of Geophysics,China Earthquake Administration (Grant Nos.DQJB21R30)。
文摘On February 6, 2023, the doublet earthquake including two main shocks with magnitudes M_(W)7.8 and M_(W)7.5, occurred near the western side of the East Anatolian Fault at the southeast boundary of the Anatolian Plateau in Turkey. Based on the WGM2012 Bouguer gravity anomaly data and the Etopo1topography data, this study first introduced a joint inversion of admittance and coherence functions and used the Bayesian optimal parameter estimation method to obtain the effective elastic thickness Teand loading ratio F of the lithosphere for various tectonic units in the Anatolian Plateau. Secondly, we discussed the characteristics and influencing factors of the lithospheric mechanical strength and analyzed its relationship with seismic activity. The lithospheric mechanical strength of the Anatolian Plateau showed clear lateral heterogeneity and a "weak-strong-weak" spatial pattern from east to west,reflecting various tectonic processes. At last, the strong seismic activity was found where the lithospheric strength was low in the Anatolian Plate. We also incorporated GPS strain rate and other results to investigate the tectonic background and primary causes of the M_(W)7.8 and M_(W)7.5 doublet earthquakes in Turkey. The results have a good insight into urban safety design in the Turkish region, including postdisaster rehabilitation, earthquake hazard assessment, and loss reduction.
基金supported financially by the Ministry of Science and Technology of China (Sinoprobe-03-02)the National Natural Science Foundation of China (Grant No. 41021063)
文摘The effective elastic thickness (Te) represents the thickness of the elastic layer or the flexural rigidity of the lithosphere, the equivalent of which can be calculated from the spectral analysis of gravity and topographic data. Studies of Te have profound influence on intracontinental deformation, and coupling of the tectonic blocks. In this paper, we use the multitaper spectral estimation method to calculate the coherence between Bouguer gravity and topography data, and to obtain the Te map of South China. Through the process of correction, we discuss the relationships of Te versus heat flow, and Te versus seismicity. The results show that Te distribution of South China is affected by three factors:the original age, which controls the basic feature;the Mesozoic evolution, which affects the Te distribution;and the neotectonic movement, which shaped the final distribution. The crust age has a positive correlation with the first-order Te distribution;thus the Yangtze Craton has a relatively higher Te (about 50 km) whereas the Te in Cathaysia block is only 10e20 km. By analysis and comparison among the tectonic models of South China, the Te distribution can be well explained using the flat-subduction model. As is typical with neotectonics, the region with a higher heat flow is related with a lower Te. The seismicity does not have a clear relationship with Te, but the strong seismicity could cause a low Te. Seismogenic layer (Ts) has a similar trend as Te in the craton, whereas in other areas the relationship is complex.
基金supported financially by the Key Foundation of the Institute of Seismology,China Earthquake Administration (No. IS201506205)the National Natural Science Foundation of China (Nos. 41504017, 41204019, 41304003)
文摘Using bathymetry and altimetric gravity anomalies, a 1°×9 1° lithospheric effective elastic thickness(Te) model over the Louisville Ridge and its adjacent regions is calculated using the moving window admittance technique. For comparison, three bathymetry models are used: general bathymetric charts of the oceans, SIO V15.1,and BAT_VGG. The results show that BAT_VGG is more suitable for calculating T e than the other two models. T e along the Louisville Ridge was re-evaluated. The southeast of the ridge has a medium Te of 10–20 km, while Te increases dramatically seaward of the Tonga-Kermadec trench as a result of the collision of the Pacific and IndoAustralian plates.
基金The National Natural Science Foundation of China under contract Nos 41976064,91958211,41890813,91858207,91628301,U1606401,41976066 and 41706056the Programs of the Chinese Academy of Sciences under contract Nos Y4SL021001,QYZDY-SSW-DQC005 and 133244KYSB20180029+1 种基金the National Key Research and Development Program of China under contract Nos2018YFC0309800 and 2018YFC0310100the China Ocean Mineral Resources R&D Association under contract No.DY135-S2-1-04
文摘We conducted a detailed analysis of along-trench variations in the flexural bending of the subducting Pacific Plate at the Tonga-Kermadec Trench.Inversions were conducted to obtain best-fitting solutions of trench-axis loadings and variations in the effective elastic plate thickness for the analyzed flexural bending profiles.Results of the analyses revealed significant along-trench variations in plate flexural bending:the trench relief(W0)of 1.9 to 5.1 km;trench-axis vertical loading(V0)of-0.5×10^12 to 2.2×10^12 N/m;axial bending moment(M0)of 0.1×10^17 to 2.2×10^17 N;effective elastic plate thickness seaward of the outer-rise region(Te^M)of 20 to 65 km,trench-ward of the outer-rise(Te^M)of 11 to 33 km,and the transition distance(Xr)of 20 to 95 km.The Horizon Deep,the second greatest trench depth in the world,has the greatest trench relief(W0 of 5.1km)and trench-axis loading(V0 of 2.2×10^12N/m);these values are only slightly smaller than that of the Challenger Deep(W0 of 5.7km and V0 of 2.9×10^12N/m)and similar to that of the Sirena Deep(W0 of 5.2 km and V0 of 2.0×10^12 N/m)of the Mariana Trench,suggesting that these deeps are linked to great flexural bending of the subducting plates.Analyses using three independent methods,i.e.,the/inversion,the flexural curvature/yield strength envelope analysis,and the elasto-plastic bending model with normal faults,all yielded similar average Te reduction of 28%-36% and average Te reduction area S△Te of 1195-1402 km^2 near the trench axis.The calculated brittle yield zone depth from the flexural curvature/yield strength envelope analysis is also consistent with the distribution of the observed normal faulting earthquakes.Comparisons of the Manila,Philippine,Tonga-Kermadec,Japan,and Mariana Trenches revealed that the average values Te^M of Te^M and both in general increase with the subducting plate age.
基金This study is supported by the postdoctoral fellowship to the senior author( Wang Yang) from Ministry of PersonnelPRC and the
文摘On the basis of more than 900 heat flow data in China and the surrounding seas, the authors study the geothermal characteristics of major tectonic units in China. The spatial pattern of heat flow and other thermal parameters for lithosphere exhibit significant lateral variation, originating from the Cenozoic tectonothermal activities related to the subduction of the Pacific plate and the collision between India and Asia. The mechanical strength of the crust and the seismicity of tectonic units were strongly affected by geothermal characteristics of units. The crustal heat production rate also shows the lateral heterogeneity, implying the significant lateral variation of bulk composition of the crust in China.
文摘Recent experiments revealed many new phenomena of the macroscopic domain patterns in the stress-induced phase transformation of a superelastic polycrystalline NiTi tube during tensile loading. The new phenomena include deformation instability with the formation of a helical domain, domain topology transition from helix to cylinder, domain-front branching and loading-path dependence of domain patterns. In this paper, we model the polycrystal as an elastic continuum with nonconvex strain energy and adopt the non-local strain gradient energy to account for the energy of the diffusive domain front. We simulate the equilibrium domain patterns and their evolution in the tubes under tensile loading by a non-local Finite Element Method (FEM). It is revealed that the observed loading-path dependence and topology transition of do- main patterns are due to the thermodynamic metastability of the tube system. The computation also shows that the tube-wall thickness has a significant effect on the domain patterns: with fixed material properties and interfacial energy density, a large tube-wall thickness leads to a long and slim helical domain and a severe branching of the cylindrical-domain front.
基金jointly supported by the National Key Basic Research Project(Grant No.G1999043302)Grants for Ph.D.in Higher University(Grant No.2000028427)Scientific Research Project of Shengli Oil field.
文摘Jiyang Depression, located in the southeast Bohai Bay Basin, has the geomorpho-logic framework of multiple uplifts intervening with sags. Combined the abundant geo-temperature data and thermo-physical parameters of rock samples derived from oil and gas exploration during the past years, with geothermal approaches, here we investigate the litho-spheric thermal regime of this depression. Consequently, based on the obtained thermal struc-ture of the lithosphere, along with rheological modeling, the lithospheric rheological profiles of Jiyang Depression are then determined. Our results show that the temperature at the bottom of sedimentary cover within depression varies from 129℃ to 298 ℃ , accompanied with the base-ment heat flow ranging between 54.3 and 60.5 mW/m2; and 406℃-436℃ for temperature at the bottom of the upper crust, along with heat flow varying from 47.7 to 52.6 mW/m2; while the tem-perature at the bottom of the middle crust is between 537 ℃ and 572 ℃, as well as heat flow ranging from 41.3 to 56.3 mW/m2. The temperature at Moho ranges from 669 ℃ to 721 ℃, the heat flow derived from mantle is between 38.1 and 43.1 mW/m2, and calculated thickness of the thermal lithosphere beneath depression varies from 71 to 90 km. Lithospheric thermal regime is a close correlation with such factors as crustal thickness and surface heat flow, etc. Usually, the larger the surface heat flow, the larger the deep temperature and heat flow within lithosphere, and the thinner the thermal lithospheric thickness. This high thermal regime of the lithosphere in Jiyang Depression is thought to be related to Cenozoic back-arc spreading during the western Pacific plate subduction into Eurasian continent. Lithospheric rheological modeling shows that the lithosphere in Jiyang Depression is characterized by its distinct rheological stratification as follows: The upper and most part of the middle crust are of brittle, while the lower crust and the lower part of middle crust are all ductile, and lithospheric mantle is dominated by the ductile layer. Additionally, lateral rheological heterogeneities exist in the depression, and the lithospheric strength of sags within depression differs much from each other. The total lithospheric strength of Jiyang Depression is between 1.52 and 2.16×1012 N/m, effective elastic thickness (Te) of the lithosphere in Jiyang Depression is about 24 km, approximating to the thickness of mechanically strong crust (MSC). We suggested that the dehydration of minerals in the subducting zone, along with upwelling of hot materials in the mantle wedge during subduction and back-arc spreading, results in the partial melting at the bottom of curst, which triggers magma intrusion and under-plating. This geodynamics process maybe is the reason for the reduction of lower crustal viscos-ity for ductile flow. Lithospheric rheological stratification controlling the differential deformation styles of brittle fracture or frictional slide in the upper crust and ductile flow in the middle and lower crust, accounts for the basin formation and evolution of Jiyang Depression during Ceno-zoic.