%0 Journal Article
%T Pn wave velocity structure and anisotropy in the central Tien Shan region<br>中天山地区的Pn波速度结构与各向异性
%A LI Zhi-Wei
%A XU Yi
%A Steven W Roecker
%A HAO Tian-Yao
%A LIU Jin-Song
%A <br>李志伟
%A 胥颐
%A Steven W. Roecker
%A 郝天珧
%A 刘劲松
%J 地球物理学报
%D 2007
%I 
%X Pn wave velocity structure and anisotropy in the central Tien Shan are investigated by using seismic arrival data from the temporary broadband network (GHENGIS) and the Kyrgyzstan seismic network (KNET). The results reveal lower average Pn velocities and strong heterogeneity at the uppermost mantle beneath the central Tien Shan, which are often found in tectonically active zones. Particularly, very low Pn velocities are found in the south-central Tien Shan, which is believed to be underlain by an unusual mantle with higher heat flows. There is a clear correlation between seismic activity and Pn velocity variation. Most earthquakes are concentrated in the north-central Tien Shan with high Pn velocities, while almost no earthquakes located in the south-central Tien Shan with very low Pn velocities. Our result suggests that the very low Pn velocity beneath the south-central Tien Shan is caused by high temperatures produced by heating from mantle upwelling, and that this heat has been conducted up into the crust, inducing a ductile rheology that prevents significant seismic activity. Moreover, strong anisotropy is observed in the north- and south-central Tien Shan. Fast Pn velocity in the south-central Tien Shan is nearly in N-S directions, which is consistent with the SKS wave anisotropy concerning mantle flow. However, fast Pn velocity directions in the north-central Tien Shan show a southward rotation variation. We estimate that it is probably related to the inserting of the crust of the Chu basin from the southern Kazakhstan platform to the central Tien Shan, which caused a change of stress fields and lithosphere deformation.
%K Central Tien Shan
%K Uppermost mantle
%K Pn velocity
%K Anisotropy<br>中天山
%K 上地幔顶部
%K Pn波速度
%K 各向异性
%U http://www.alljournals.cn/get_abstract_url.aspx?pcid=E62459D214FD64A3C8082E4ED1ABABED5711027BBBDDD35B&cid=1E44AE713D8A6DE0&jid=14DC41C59CBF6770055A7D610D53AE46&aid=60CAC8C493F0F357&yid=A732AF04DDA03BB3&vid=771152D1ADC1C0EB&iid=E158A972A605785F&sid=63025EFC6CC49145&eid=AF41770817DB8958&journal_id=0001-5733&journal_name=地球物理学报&referenced_num=2&reference_num=29