Finite Difference Tomography of the Crustal Velocity Structure in Tengchong, Yunnan Province
详细信息
- 责任者：Cao Lingmin (Marine Geology and Environment Key Laboratory ; Institute of Oceanology ; Chinese Academy of Sciences ; Qingdao 266071 ; China) ; Xu Yi
- 刊名：Chinese Journal of Geophysics
- 出版年：2013
- 卷期：56(4)
- 关键词：地壳 ; crust ; 速度结构 ; velocity structure ; 云南 ; Yunnan Province
- 页码：p.1159-1167
- 图表：illus., 35 refs.
- 分类号：0400
- issnNo：ISSN0001-5733
- isbnNo：CN11-2074/P
摘要
This paper applies the finite difference tomography method to invert for the P-wave velocity structure in the Tengchong area using earthquake data from a temporary network and other permanent stations,and analyzes the magmatic activity of the Tengchong volcanoes and the deep tectonic genesis of Longling M7.3/M7.4 earthquakes.The results show the mean velocity in the crust with clear heterogeneity is a little lower.The lower velocities in the shallow layers are caused by unconsolidated basin deposits,Cenozoic volcanic deposits,fluid fractures and hot springs.The high-velocity zone at 5~15 km depth probably represents the cooled and solidified magmatic intrusions or the less volatile ultramafic remnants.The low-velocity structure in the deep indicates the molten or semi-molten magma.It is probable that the magmatic activity beneath the volcanoes and heat flow intrusions in the deep crust of Longling earthquake zone are from the same magmatic hearth area,which is the main area of the present magmatic activities.A strong lateral heterogeneity is observed in Longling earthquake zone.The east of the Nujiang fault belt and the west of the Longling fault belt have the characters of high-velocity with the high strength of rock,which are the main bearing body of stress accumulation.However,the low-velocity anomaly between the two faults extends to lower crust,probably caused by magmatic intrusions in the deep crust.The magmatic activity in this area is controlled clearly by the Longling fault and the Nujiang fault.The Longling M7.3 and M7.4 earthquakes occurred near the velocity boundary beneath the faults.The main reasons of the strong earthquakes in the Longling area contain the heterogeneity of stress accumulation caused by the lateral variation of the crustal medium strength,the deep magmatic aggregation and dynamic effects.