中国东北地壳结构的地震层析成像  

Seismic Tomography of the Crustal Structure in Northeast China

作　　者：李洪丽[1] 刘财[1,2] 田有[1,2] 范豪 Li Hongli;Liu Cai;Tian You;Fan Hao(College of GeoExploration Science and Technology,Jilin University,Changchun 130026,China;Changbai Volcano Geophysical Observatory,Ministry of Education,Changchun 130026,China)

机构地区：[1]吉林大学地球探测科学与技术学院,长春130026 [2]长白山火山综合地球物理教育部野外科学观测研究站,长春130026

出　　处：《吉林大学学报（地球科学版）》2022年第1期270-280,共11页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(41874049);国家重点研发计划项目(2017YFC0601300);吉林省重点科技攻关项目(20200403068SF)。

摘　　要：中国东北地区自晚古生代晚期以来,受古亚洲洋、蒙古—鄂霍茨克洋、太平洋构造域的叠加作用,壳幔结构极为复杂。本文收集中国东北地区国家地震台网接收的100 980个P波和91 030个S波到时数据,采用地震走时层析成像方法获得了该地区地壳P波和S波速度结构,进而获得了泊松比结构,用以探讨复杂的地壳结构。成像结果显示:中国东北地区地壳地震波速度结构呈明显的横向不均匀性,不同构造单元和构造单元内部都存在不同程度的不均匀性。松辽盆地整体上浅层地壳以低速异常为主,尤其是S波速度,但部分区域分辨率较低,中下地壳存在较大范围高速异常,推测与太平洋俯冲、后撤导致的岩石圈拆沉和热物质上涌等动力学过程有关;北部的大兴安岭重力梯级带和长白山一线主要表现为低速异常,表明具有大范围的岩浆作用,广泛岩浆作用为固体矿产资源的形成提供热源或物源;长白山、五大连池等近代活动的火山下方部分地壳区域均表现了较强低地震波速度和高泊松比异常结构特征,表明仍存在活动的可能。Since the Late Paleozoic,Northeast China has experienced the combined effect of Paleo-Asian Ocean,Mongolia-Okhotsk Sea,and Pacific tectonic domain,resulting in the extremely complex crust-mantle structure.In this study,we collected 100 980 P-wave arrival times and 91 030 S-wave arrival times compiled by the National Earthquake Network,and the 3-D P-and S-wave velocity structures in Northeast China were determined by using seismic tomography method.The Poisson’s ratio structure of the study region was also obtained to explore its complex crustal structure.The tomographic results show that the crustal velocity structure in Northeast China exhibits strong lateral heterogeneities with various degrees of heterogeneity between and within different tectonic units.The Songliao basin is a typical rift basin.The shallow crust shows low P-wave and significantly low S-wave anomalies as a whole,with some low resolution regions.Large-scale high-velocity anomalies exist in the middle and lower crust,which may be related to the subduction and retreat of the Pacific plate beneath the Eurasian continent,resulting in the lithospheric delamination and upwelling of hot and wet asthenosphere material.The northern part of the Great Xing’an Range gravity lineament and the Changbai Mountain show low-velocity anomalies,which may indicate large-scale magmatism.The widespread magmatism may provide heat or material sources for the formation of solid mineral resources.The crust beneath Changbai Mountain and Wudalianchi volcanic areas shows significant low velocity and high Poisson’s ratio anomalies,which may indicate the possibility of volcanic activities.

关 键 词：地震层析成像 中国东北 地壳结构 泊松比结构 活火山 

分 类 号：P315[天文地球—地震学]