Three Dimensional P-Wave Velocity Structure around Xiaojiang Fault System and Its Tectonic Implications
详细信息
- 责任者：Wu Jianping (Institute of Geophysics ; China Earthquake Administration ; Beijing 100081 ; China) ; Yang Ting
- 刊名：Chinese Journal of Geophysics
- 出版年：2013
- 卷期：56(7)
- 关键词：速度结构 ; velocity structure ; 三维地震法 ; three-dimensional seismic methods ; 青藏高原 ; Qinghai-Tibetan Plateau
- 页码：p.2257-2267
- 图表：5 illus., 48 refs.
- 分类号：0400
- issnNo：ISSN0001-5733
- isbnNo：CN11-2074/P
摘要
As the southeastern margin of Tibetan Plateau,Xiaojiang fault system plays an important role in the lateral escape of Tibetan Plateau materials.In this paper,3-D P-wave velocity structure in Xiaojiang fault system and its surrounding areas was imaged by using travel time data from permanent seismic stations and a dense temporal seismic array.The results show that in the upper and middle crust,Xiaojiang fault system mainly represents low velocity,while high velocity anomalies exist to its east.In the middle and lower crust,a low velocity anomaly is shown in the central area of Xiaojiang fault system,and high velocity anomalies exist both in the northern and southern areas.The northern high velocity anomaly near Panzhihua extends from lower crust to the surface,and the southern one in the lower crust extends to the upper mantle.We consider that the low velocity anomaly in the central area of Xiaojiang fault system is caused by high temperature derived from upper mantle.The high velocity anomalies in the northern area are most likely related to the late Paleozoic mantle plume activity which caused a large amount of basic and ultrabasic mantle material intruded into the crust.These high velocity anomalies,with greater mechanical strength,play a certain impediment to southward escaping of Tibetan Plateau materials,and lead to the rapid uplift of the northern sub-block of the Sichuan-Yunnan active block.The north-dipping high velocity anomaly in the southern area is a further barrier for southward extrusion of Sichuan-Yunnan active block,leading to strong deformation and high rate of seismicity within the low velocity area in the overlying upper and middle crust.Meantime,this high velocity block contributes to stabilization in the upper mantle,which causes mantle materials of its southern region less affected by the southward escape of Tibetan Plateau materials.
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