The uppermost mantle is the key area for exchange of heat flux and material convection between the crust and lithospheric mantle. Spatial variations of lithospheric thinning and dynamic processes in the North China Cr...The uppermost mantle is the key area for exchange of heat flux and material convection between the crust and lithospheric mantle. Spatial variations of lithospheric thinning and dynamic processes in the North China Craton could inevitably induce the velocity heterogeneity in the uppermost mantle.In this study,we used Pn arrivals from permanent seismic stations in North China and surrounding regions to construct a tomographic image of the North China Craton.The tomographic method with Pn travel time difference data were used to study the velocity variations in the uppermost mantle.Pn velocities in the uppermost mantle varied significantly in the Eastern,Central and Western blocks of the North China Craton.This suggests that the lithosphere beneath different blocks of the North China Craton have experienced distinct tectonic evolutions and dynamic processes since the Paleo- zoic.The current uppermost mantle has been imprinted by these tectonic and dynamic processes.Fast Pn velocities are prominent beneath the Bohai Bay Basin in the Eastern Block of the North China Craton,suggesting residuals of the Archean lithospheric mantle.Beneath the Tanlu Fault Zone and Bohai Sea,slow Pn velocities are present in the uppermost mantle,which can be attributed to significant lithospheric thinning and asthenospheric upwelling.The newly formed lithospheric mantle beneath Yanshan Mountain may be the dominant reason for the existence of slow Pn velocities in this region.Conversely,the ancient lower crust and lithospheric mantle already have been delaminated.In the Central Block,significant slow Pn velocities are present in Taihangshan Mountain,which also extends northward to the Yinchuan-Hetao Rift on the northern margin of the Ordos Block and Yinshan Orogen.This characteristic probably is a result of hot asthenospheric upwelling along the active tectonic boundary on the margin of the Western Block.The protracted thermal erosion and underplating of hot asthenospheric upwelling may induce lithospheric thinning and significant slow vel展开更多
In order to ensure on-time arrival when travelersmake their trips, the stochastic network assignment modelunder uncertainty of travel time is investigated. First, basedon travelers＇ route choice behavior, the reliabl...In order to ensure on-time arrival when travelersmake their trips, the stochastic network assignment modelunder uncertainty of travel time is investigated. First, basedon travelers＇ route choice behavior, the reliable travel timeconfidence level （RTTCL）, which is the probability that a triparrives within the shortest average travel time plus theacceptable travel time difference, is defined. Then, areliability-based user equilibrium （RUE） model, whichhypothesizes that for each OD pair no traveler can improvehis/her RTTCL by unilaterally changing routes, is built.Since the traditional traffic assignment algorithms are notfeasible to solve the RUE model, a quasi method of successiveaverage （QMSA） is developed. Using Nguyen-Dupuis andSioux Falls networks, the model and the algorithm are tested.The results show that the QMSA algorithm can rapidlyconverge to a high accuracy for solving the proposed RUEmodel, and the RUE model can provide a good response totravelers＇ behavior in the stochastic network.展开更多
基金supported by the National Natural ScienceFoundation of China (90814011)Open Fund of Key Laboratory of Geodetection (China University of Geosciences, Beijing),Ministry of Education (GDL0905)+1 种基金Fund of China Geological Survey (GZH200900504)the China Postdoctoral Science Foundation (20090460511)
文摘The uppermost mantle is the key area for exchange of heat flux and material convection between the crust and lithospheric mantle. Spatial variations of lithospheric thinning and dynamic processes in the North China Craton could inevitably induce the velocity heterogeneity in the uppermost mantle.In this study,we used Pn arrivals from permanent seismic stations in North China and surrounding regions to construct a tomographic image of the North China Craton.The tomographic method with Pn travel time difference data were used to study the velocity variations in the uppermost mantle.Pn velocities in the uppermost mantle varied significantly in the Eastern,Central and Western blocks of the North China Craton.This suggests that the lithosphere beneath different blocks of the North China Craton have experienced distinct tectonic evolutions and dynamic processes since the Paleo- zoic.The current uppermost mantle has been imprinted by these tectonic and dynamic processes.Fast Pn velocities are prominent beneath the Bohai Bay Basin in the Eastern Block of the North China Craton,suggesting residuals of the Archean lithospheric mantle.Beneath the Tanlu Fault Zone and Bohai Sea,slow Pn velocities are present in the uppermost mantle,which can be attributed to significant lithospheric thinning and asthenospheric upwelling.The newly formed lithospheric mantle beneath Yanshan Mountain may be the dominant reason for the existence of slow Pn velocities in this region.Conversely,the ancient lower crust and lithospheric mantle already have been delaminated.In the Central Block,significant slow Pn velocities are present in Taihangshan Mountain,which also extends northward to the Yinchuan-Hetao Rift on the northern margin of the Ordos Block and Yinshan Orogen.This characteristic probably is a result of hot asthenospheric upwelling along the active tectonic boundary on the margin of the Western Block.The protracted thermal erosion and underplating of hot asthenospheric upwelling may induce lithospheric thinning and significant slow vel
基金The National Natural Science Foundation of China(No.51608115,51578150,51378119)the Natural Science Foundation of Jiangsu Province(No.BK20150613)+2 种基金the Scientific Research Foundation of Graduate School of Southeast University(No.YBJJ1679)the Scientific Innovation Research of College Graduates in Jiangsu Province(No.KYLX15_0150)the China Scholarship Council(CSC)Program
文摘In order to ensure on-time arrival when travelersmake their trips, the stochastic network assignment modelunder uncertainty of travel time is investigated. First, basedon travelers＇ route choice behavior, the reliable travel timeconfidence level （RTTCL）, which is the probability that a triparrives within the shortest average travel time plus theacceptable travel time difference, is defined. Then, areliability-based user equilibrium （RUE） model, whichhypothesizes that for each OD pair no traveler can improvehis/her RTTCL by unilaterally changing routes, is built.Since the traditional traffic assignment algorithms are notfeasible to solve the RUE model, a quasi method of successiveaverage （QMSA） is developed. Using Nguyen-Dupuis andSioux Falls networks, the model and the algorithm are tested.The results show that the QMSA algorithm can rapidlyconverge to a high accuracy for solving the proposed RUEmodel, and the RUE model can provide a good response totravelers＇ behavior in the stochastic network.
