Suspended sediment concentrations in the Middle Yangtze River(MYR)reduced greatly after the Three Gorges Project operation,causing the composition of bed material to coarsen continuously.However,little is known about ...Suspended sediment concentrations in the Middle Yangtze River(MYR)reduced greatly after the Three Gorges Project operation,causing the composition of bed material to coarsen continuously.However,little is known about the non-equilibrium transport of graded suspended sediment owing to different bed material compositions(BMCs)along the MYR,and it is necessary to determine the magnitude of recovery factor.Using the Markov stochastic process in conjunction with the hiding-exposure effect of non-uniform bed-material,a new formula is proposed for calculating the recovery factor including the effect of different BMCs,and it is incorporated into the non-equilibrium transport equation to simulate the recovery processes of suspended load in both sand-gravel bed and sand bed reaches of the MYR.The results show that:(i)the recovery rate of graded sediment concentrations at Zhicheng was slower than that at Shashi during the period 2003-2007;(ii)the mean recovery factors of the coarse,medium,and fine sediment fractions in the ZhichengShashi reach were 0.152,0.0012,and 0.0005,respectively,and the coarse sediment recovered up to the maximum sediment concentration of 0.138 kg/m3over a distance of 15 km;and(iii)the results of the new formula that can consider the effect of bed material composition are in general agreement with the field observations,and the spatial and temporal delay effects are inversely related to particle size and BMC.Consequently,the BMC effect on the nonequilibrium sediment transport in different reaches of the MYR needs to be considered for higher simulation accuracy.展开更多
To better understand the mechanism of the Mw6.3 L'Aquila(Central Italy) earthquake occurred in 2009,global positioning system(GPS) and interferometric synthetic aperture radar(InSAR) data were used to derive the c...To better understand the mechanism of the Mw6.3 L'Aquila(Central Italy) earthquake occurred in 2009,global positioning system(GPS) and interferometric synthetic aperture radar(InSAR) data were used to derive the coseismic slip distribution of the earthquake fault.Firstly,based on the homogeneous elastic half-space model,the fault geometric parameters were solved by the genetic algorithm.The best fitting model shows that the fault is a 13.7 km×14.1 km rectangular fault,in 139.3° strike direction and 50.2° southwest-dipping.Secondly,fixing the optimal fault geometric parameters,the fault plane was extended and discretized into 16×16 patches,each with a size of 1 km×1 km,and the non-uniform slip distribution of the fault was inverted by the steepest descent method with an appropriate smoothing ratio based on the layered crustal structure model.The preferred solution shows that the fault is mainly a normal fault with slight right-lateral strike slip,the maximum slip of 1.01 m is located in the depth of 8.28 km,the average rake is -100.9°,and the total geodetic moment is about 3.34×1018 N·m(Mw 6.28).The results are much closer than previous studies in comparison with the seismological estimation.These demonstrate that the coseismic fault slip distribution of the L'Aquila earthquake inverted by the crustal model considering layered characters is reliable.展开更多
基金the National Natural Science Foundation of China(Grant Nos.51725902,52009095,U2040215,U2240206,and 52109098)supported partly by the Postdoctoral Research Foundation of China(Grant No.BX2021228)Natural Science Foundation of Hubei Province(Grant No.2021CFA029)。
文摘Suspended sediment concentrations in the Middle Yangtze River(MYR)reduced greatly after the Three Gorges Project operation,causing the composition of bed material to coarsen continuously.However,little is known about the non-equilibrium transport of graded suspended sediment owing to different bed material compositions(BMCs)along the MYR,and it is necessary to determine the magnitude of recovery factor.Using the Markov stochastic process in conjunction with the hiding-exposure effect of non-uniform bed-material,a new formula is proposed for calculating the recovery factor including the effect of different BMCs,and it is incorporated into the non-equilibrium transport equation to simulate the recovery processes of suspended load in both sand-gravel bed and sand bed reaches of the MYR.The results show that:(i)the recovery rate of graded sediment concentrations at Zhicheng was slower than that at Shashi during the period 2003-2007;(ii)the mean recovery factors of the coarse,medium,and fine sediment fractions in the ZhichengShashi reach were 0.152,0.0012,and 0.0005,respectively,and the coarse sediment recovered up to the maximum sediment concentration of 0.138 kg/m3over a distance of 15 km;and(iii)the results of the new formula that can consider the effect of bed material composition are in general agreement with the field observations,and the spatial and temporal delay effects are inversely related to particle size and BMC.Consequently,the BMC effect on the nonequilibrium sediment transport in different reaches of the MYR needs to be considered for higher simulation accuracy.
基金Projects(40974006,40774003) supported by the National Natural Science Foundation of ChinaProject(NCET-08-0570) supported by the Program for New Century Excellent Talents in Chinese Universities+2 种基金Projects(2011JQ001,2009QZZD004) supported by the Fundamental Research Funds for the Central Universities in ChinaProjects(09K005,09K006) supported by the Key Laboratory for Precise Engineering Surveying & Hazard Monitoring of Hunan Province,ChinaProject(1343-74334000023) supported by the Graduate DegreeThesis Innovation Foundation of Central South University,China
文摘To better understand the mechanism of the Mw6.3 L'Aquila(Central Italy) earthquake occurred in 2009,global positioning system(GPS) and interferometric synthetic aperture radar(InSAR) data were used to derive the coseismic slip distribution of the earthquake fault.Firstly,based on the homogeneous elastic half-space model,the fault geometric parameters were solved by the genetic algorithm.The best fitting model shows that the fault is a 13.7 km×14.1 km rectangular fault,in 139.3° strike direction and 50.2° southwest-dipping.Secondly,fixing the optimal fault geometric parameters,the fault plane was extended and discretized into 16×16 patches,each with a size of 1 km×1 km,and the non-uniform slip distribution of the fault was inverted by the steepest descent method with an appropriate smoothing ratio based on the layered crustal structure model.The preferred solution shows that the fault is mainly a normal fault with slight right-lateral strike slip,the maximum slip of 1.01 m is located in the depth of 8.28 km,the average rake is -100.9°,and the total geodetic moment is about 3.34×1018 N·m(Mw 6.28).The results are much closer than previous studies in comparison with the seismological estimation.These demonstrate that the coseismic fault slip distribution of the L'Aquila earthquake inverted by the crustal model considering layered characters is reliable.
