基于背景噪声反演的兴蒙造山带阿巴嘎地区地壳S波速度结构  

Crustal S-wave velocity structure of the Abaga area of Xing’an-Mongolia Orogenic Belt from ambient noise

作　　者：徐荟[1,2] 吴庆举[1,2] Xu Hui;Wu Qingju(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Key Laboratory of Earthquake Source Physics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局震源物理重点实验室,北京100081

出　　处：《地震学报》2025年第1期54-72,共19页Acta Seismologica Sinica

基　　金：国家自然科学基金(41274088,41674094,41874112)联合资助。

摘　　要：利用布设于兴蒙造山带内蒙古中部阿巴嘎台阵记录的连续背景噪声数据,获取了研究区内周期为5—30 s的瑞雷面波频散,使用马尔科夫链-蒙特卡洛反演方法建立了阿巴嘎地区地壳高分辨率三维S波速度结构。结果显示,阿巴嘎和达里诺尔火山区上中下地壳的S波速度均呈低速,且下地壳30 km处存在明显的低速区,推断该处可能为下地壳的岩浆囊及上方岩浆通道。此外,阿巴嘎、达里诺尔、达里甘嘎和乌兰哈达火山群在地壳内的低速区都是相互连通的。结合前人研究结果,推测出阿巴嘎和达里诺尔火山群的岩浆源区位于上地幔顶部,并且进一步推测阿巴嘎和达里诺尔火山群的形成是源于区域内地幔热物质上涌,沿缝合带或断层侵入到地壳诱发了地表火山活动。Cenozoic intraplate volcanoes are widely developed in the central part of Inner Mongolia in the Xing’an-Mongolia Orogenic Belt.These volcanoes are mainly distributed in groups to the west of the Greater Xing’an-Taihang Mountain Gravity Lineament,forming a number of volcanic regions,such as Abaga,Beilike and Dalinor volcanic regions.And these three volcanic regions are connected with the Dariganga volcanic region in southern Mongolia.The origin and dynamic mechanism of these Cenozoic intraplate volcanoes is still a controversial topic.Previous studies have mainly proposed the following three mechanisms:lithosphere delamination;upwelling of mantle plume in mantle transition zone;westward subduction of the Pacific plate.In this study,to further reveal the magma structure and origin of these intraplate volcanoes,a high-resolution 3-D S-wave velocity structure of the crust in the study area was established.Based on the continuous data of the Abaga Array deployed in the central part of Inner Mongolia in the Xing’an-Mongolia Orogenic Belt,the Rayleigh surface wave dispersion with period range of 5 s to 30 s was obtained.Then the high-resolution 3-D S-wave velocity structure of the crust was further obtained by using the Markov Chain Monte Carlo method.The results show the crustal velocity of the Abaga and Dalinor volcanic group is low,and there is an obvious low velocity zone at about 30 km depth in the lower crust,which may be the magma chamber in the lower crust of the volcanic groups.The results also imply the low velocity in the crust of Abaga volcanic group,Dalinor volcanic group,Dariganga volcanic group and Ulanhada volcanic group are interconnected.According previous results,the magma sources of the Abaga volcanic group and the Dalinor volcanic group are in the uppermost layer of the upper mantle.Furtherly it is speculated that the formation of the Abaga and Dalinor volcanic group is due to the upwelling of hot material in the upper mantle,which invaded the crust along the suture zones or faults.

关 键 词：兴蒙造山带阿巴嘎 阿巴嘎火山群 达里诺尔火山群 背景噪声 S波速度 

分 类 号：P315.3[天文地球—地震学]