利用区域双差层析成像方法研究川滇南部地壳结构特征  

Analysis on crustal structure characteristics of southern Sichuan-Yunnan by regional double-difference seismic tomography

作　　者：邓山泉 章文波 于湘伟 宋倩 王小娜[2] DENG ShanQuan;ZHANG WenBo;YU XiangWei;SONG Qian;WANG XiaoNa(College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Earthquake Administration of Guangdong Province,Guangzhou 510000,China)

机构地区：[1]中国科学院大学地球与行星科学学院,北京100049 [2]广东省地震局,广州510000

出　　处：《地球物理学报》2020年第10期3653-3668,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41374105,41604055)资助.

摘　　要：本文联合使用云南、四川和贵州地震台网的85个地震台站在2008年1月—2017年12月期间记录的49130个地震、317366个初至Pg震相绝对到时数据和2674110条高精度的相对到时数据,采用区域双差地震层析成像方法联合反演了川滇南部地壳三维P波速度结构和39621个地震的震源参数,探究了川滇南部中下地壳流和腾冲火山区岩浆囊的分布特征.研究结果表明:(1)川滇南部上地壳的速度异常特征与地表地形密切相关;(2)小江断裂带的中下地壳存在一条绵延近二百多公里的低速异常结构,最南端受到红河断裂带的阻挡而终止于断裂带南段北侧,这可能是川滇南部的一条中下地壳流,低速异常结构在红河断裂带南段转而向南东流动反映了红河断裂带可能为川滇菱形块体的西南边界;(3)红河断裂带各段速度异常存在明显的差异,重定位后的震源分布显示红河断裂带中段和南段虽然不如北段地震活动强烈,但地震震源深度分布较北段深;(4)腾冲火山区西侧和北侧下方10~20 km深度范围内存在的低速异常体推测为通过怒江断裂带形成的岩浆通道从中地壳涌入上地壳的岩浆囊,可能反映了自更新世延续至今的以橄榄玄武岩和安山岩为主要岩性的壳内岩浆活动,持续的岩浆活动为地表热活动提供了主要动力.The regional double-difference seismic tomography(tomoFDD)was applied to 317366 first Pg absolute arrival times and 2674110 high quality relative Pg arrival times of 49130 earthquakes recorded by 85 seismic stations of Yunnan,Sichuan and Guizhou Seismic Networks from January 2008 to December 2017.Detailed crustal 3D P-wave velocity structure and the hypocenter parameters of 39621 earthquakes were simultaneously determined in southern Sichuan-Yunnan(SSY).The 3D velocity structure provides distribution characteristics for the middle-lower crustal flow and magma of Tengchong volcanic area.The results show velocity anomalies of the upper crust in SSY are closely related to the surface topography.A low velocity anomaly extends more than 200 km in the middle and lower crust of the Xiaojiang fault zone.The southernmost end of the low velocity anomalies is blocked by the Red River fault and ends at the north side of the southern segment of the fault zone.An obvious low-velocity anomaly is visible in the middle and lower crust beneath SSY area,which may reflect the weak material flow in the middle and lower crust in the southeastern margin of Tibetan Plateau.The low velocity anomalies beneath the southern segment of the Red River fault zone turn to southeastward,which further shows that the Red River fault may be the southwestern boundary of Sichuan-Yunnan rhombic block.There are obvious differences in the velocity anomalies of each segment of the Red River fault.The focal distribution after relocation shows that the activity in the middle and southern segments of the Red River fault zone is not as strong as that in the northern segment.However,the focal depth is deeper than that of the northern segment.An obvious low-velocity anomaly in the depth range of 10~20 km in the west and north of Tengchong volcanic area may be the magma from middle to upper crust through magma channel formed by Nujiang fault.The low-velocity anomalies may represent the intra-crustal magmatic activity with olivine basalt and andesite as the main

关 键 词：川滇南部 地壳速度结构 地壳流 腾冲火山区 

分 类 号：P315[天文地球—地震学]