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Seismic tomography beneath the orogenic belts and adjacent basins of northwestern china

Science china.Earth Sciences 2001年第5期44卷 468-480页

作者：胥颐刘福田刘建华孙若昧 Institute of Geophysics Chinese Academy of Sciences Beijing China

Three-dimensional velocity images of the crust and upper mantlebeneath orogenic belts and adjacent basins of the northwestern continent of china.are reconstructed by seismic tomography, based on arrival data of P wave recorded in seismic networks in Xinjiang, Qinghai, Gansu of china.and Kyrgyzstan. The velocity images of upper crust demonstrate the tectonic framework on the ground surface. High velocities are observed beneath orogenic belts, and low velocities are observed in the basins and depressions that are obviously related to unconsolidated sediments. The velocity image in mid-crust maintains the above features, and in addition low velocities appear in some earthquake regions and a low velocity boundary separates the western Tianshan Mts. from eastern Tianshan Mts. The orogenic belts and the northern Tibetan plateau have a Moho depth over 50 km, whereas the depths of the Moho in basins and depressions are smaller than 50 km. The velocity images of upper mantle clearly reveal the colliding relationship and location of deep boundaries of the continental blocks in northwestern china. indicating a weakness of the upper mantle structure of orogenic belts. The top depth of upper mantle asthenosphere varies from place to place. It seems shallower under the northern Tibetan plateau, Altay and Qilian Mts., and deeper under the Tarim and Tianshan regions. Hot mantle probably rose to the bottom of some orogenic belts along tectonic boundaries when continental blocks collided to each other. Therefore their dynamic features are closely correlated to the formation and evolution of orogenic belts in northwestern china.

关键词： seismic tomography orogenic belt northwestern china.

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Investigation of Aerosol Optical Depth(AOD) and ?ngstr?m Exponent over the Desert Region of northwestern china.Based on Measurements from the china.Aerosol Remote Sensing Network(CARSNET)

Investigation of Aerosol Optical Depth(AOD) and ?ngstr?m Exp...

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第32届中国气象学会年会

作者： Jie Yu Huizheng Che Quanliang Chen Xiangao Xia Hujia Zhao Hong Wang Yaqiang Wang Xiaoye Zhang Guangyu Shi Plateau Atmospheric and Environment Key Laboratory of Sichuan Province College of Atmospheric Sciences Chengdu University of Information Technology Key Laboratory for Atmospheric Chemistry Institute of Atmospheric Composition Chinese Academy of Meteorological Sciences CMA Jiangsu Collaborative Innovation Center of Climate Change Laboratory for Middle Atmosphere and Global Environment Observation Institute of Atmospheric Physics Chinese Academy of Sciences Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science & Technology Institute of Atmospheric Environment China Meteorological Administration State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) Institute of Atmospheric Physics Chinese Academy of Sciences

Aerosols at ten sites in northwestern china.are classified in this study:(1)by using the aerosol optical depth(AOD),the?ngstr?m exponent(α)and the?ngstr?m exponent difference(δα);and(2)by using the total means of AOD440nm andα.The seasonal variations of the AOD andαshow that the maximum AODs occur in spring,except at Urumqi and *** seasonal meanαvalues are lower than 0.80 in all four seasons at Tazhong,Hotan,Hami,Ejina,Dunhuang,Minqin,and Jiuquan,but higher than 0.80 in winter at Urumqi,Lanzhou and *** first classification method shows that coarse mode particles are found at all ten sites,but that fine mode growth only happens at Urumqi,Lanzhou,and *** relationship between AOD440nm andαshow thatαsmaller than 0.80decrease with increasing AOD440nm at all ten *** are classified into four types(Type I–IV)according to the total meanτ440(440?)and total mean?ngstr?m exponent(?)of each *** with aτ440 smaller than 440?,but greater than or equal to?(τ440<440?;α≥?)are classified as Type I;aerosols withτ440≥440?andα≥?are Type II;those withτ440<440?andα

关键词： Aerosol optical depth(AOD) ?ngstr?m exponent(α) Aerosol classification northwestern china.

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