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南极中山站-昆仑站间地壳厚度分布

         

摘要

Since the 4th International Polar Year in 2007/2008 until 201 3,the Chinese have deployed cold-mode very-broadband seismic stations along the traverse from Zhongshan to Kunlun (Dome A),East Antarctica.Using obser-vations recorded by the stations,we retrieved the S-receiver functions of seven stations from seismic waveform data, and inverted them for crustal thicknesses beneath the stations using the receiver functions.The results show that the crustal thickness increases along the traverse from 38 km beneath Zhongshan Station to approximately 58 km be-neath EAGLE and CHNB.The thickness then decreases to 47 km beneath CHNA,and finally increases to 62 km beneath the highest point of Antarctica,at Kunlun Station (Dome A).This thickness variation is consistent with the bedrock surface variation along the path,and indicates that the tectonics between Zhongshan and CHNB are rel-atively homogeneous.The crustal thickness beneath Kunlun Station of Dome A is not only the largest in Antarctica, but is also substantially greater than that beneath the cratons of other continents.The crust beneath CHNA is ap-proximately 1 0 km thinner than at neighboring stations,which may be due to the short duration of observations at the station,and may indicate that the crustal structure lateral variation is very large beneath the Gamburtsev Subgla-cial Mountains.%自第4个国际极地年2007/2008开始至2013年,中国南极内陆冰盖科考队相继在自南极大陆边缘的中山站至东南极地形最高点昆仑站(Dome A)一线进行了低温甚宽频地震观测。本文对7个天然地震台站数据进行了分析,提取了这些台站的S波接收函数,据此反演获得了这些台站下的地壳厚度分布。结果显示:随着纬度的升高,地壳厚度由大陆边缘的中山站下的约38 km逐渐增加至CHNB台下的58 km,随后又于CHNA台站下方减薄至47 km,然后快速增大到南极地形最高点昆仑站(Dome A)下的62 km。昆仑站或Dome A是南极大陆地壳最厚的地方。从中山站至昆仑站之间地壳厚度的变化与冰下地貌变化存在明显的相关性,它们都说明了从中山站至CHNB之间地壳构造相对均匀。在距昆仑站约200 km的CHNA台下的地壳厚度(约47 km)明显比临近台站地壳偏薄,这可能说明了甘伯采夫山脉地壳侧向变化较大,即其形成时所遭受的构造作用较复杂。

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