中国东北地区高分辨率地壳结构:远震接收函数

利用分布在东北地区的国家地震局台网、NECESSArray台网、吉林大学在长白山及其周边地区布设的26个临时台站总计259个台站接收到的16,070条高质量的P波接收函数,采用H-k和CCP(Common Conversion Point,共转换点)叠加成像方法,获得该区高分辨率的地壳结构.观测结果显示,东北地区莫霍界面深度和地表高程总体呈镜像关系;西部大兴安岭—太行山重力梯级带附近存在莫霍界面深度陡变带;中部的松辽盆地地区受晚中生代的地壳拉伸作用影响,地壳厚度较薄,北部的小兴安岭地区和南部的华北北缘造山带可能同样受拉伸运动影响,具有较小的地壳厚度;松辽盆地莫霍界面深度由西向东逐渐减小,推测这与太平洋板块俯冲作用有关;东部地区莫霍界面结构比较复杂,依兰—伊通断裂与敦化—密山断裂之间出现复杂震相,可能与该区存在地幔物质的底侵作用有关;长白山火山地区地壳厚度较大,对应较高的波速比,推测在该区地壳内存在岩浆囊.

High-resolution crustal structure of Northeast China revealed by teleseismic receiver functions

In this work, we study the high-resolution crustal structure of Northeast China by using the receiver function method. A total of 259 stations which consist of the China Earthquake Administration, NECESSArray stations and 26 Jilin University temporary stations are used in this study, and finally 16070 high-quality receiver functions are selected. We use the H-κ and CCP stacking methods to obtain a high-resolution crustal structure beneath Northeast China. The results show that the Moho depth beneath the study area generally coincides a mirror relationship with the surface elevation. Below the west portion of the Great Xing'an Range, there exists an abrupt change of the Moho depth. In the center of the study area, the crust of the Songliao basin is very thin, which is associated with the regional tectonic extension in the late Mesozoic. In the Songliao basin, the variation of Moho is decreasing from west to east, and we speculate it is related to the subducting Pacific slab. The east part of the study area has a complicated Moho structure, and multiple phases can be observed between the Yilan-Yitong and Dunhua-Mishan faults, which may relate to the mantle-material's underplating. Around the Changbai volcano area, a thick crust and high V_P/V_S structure are observed, which indicates that the magma chambers probably exist in the crust.