摘要
2011年8月至2013年7月中国地震局地球物理研究所与蒙古科学院天文与地球物理研究中心在蒙古中南部区域布设了宽频带流动地震台阵,这为开展远东地区深部结构的精细探测提供了有利的数据基础.利用台阵记录的远震地震事件,采用P波接收函数的H——(-κ)叠加分析和共转换点(CCP)叠加方法获得了台站下方的地壳厚度及平均波速比.结果显示研究区的地壳厚度介于39 km至45 km之间.整体上Moho面埋深从西北往东南方向逐渐变浅.在蒙古主线性构造两侧地壳厚度呈现区域性变化特征,东南部地区地壳厚度较薄,约为39 km,而西北部地区地壳较厚,达45 km,为此推测蒙古主构造线可能是地壳的一个陡变带.此外,研究地区地壳的平均波速比值(V_p/V_s)在1.70到1.79之间,均值为1.75,低于全球大陆的平均值1.78,这可能暗示着该区其地壳是缺少铁镁质的.研究还发现测线的西北与东南地区其地壳波速比值较高,推测是古生代铁镁质地壳的残留或是新生代岩浆底侵的反映.
A broadband digital seismic array was deployed by the Institute of Geophysics, CEA and Research Center of Astronomy κ Geophysics, Mongolian Academy of Sciences in the central and southern Mongolia, from August 2011 to July 2013. The purpose is to probe the fine deep structure below the Far East. We use the teleseismic events recorded by this array to calculate the P wave receiver functions and obtain crustal thickness and velocity ratio （Vp/Vs） by the H-κ stacking and CCP stacking method. The results show that crustal thickness of the study area is between 39 km and 45 km. The Moho becomes gradually shallower from the northwest to southeast. There exists a regional variation across the MML （Main Mongolian Lineament）, in the southeast of which the crustal thickness is thinner about 39 km and in the northwest of which it is thicker over 45 km. We speculate that the MML may he a sharp change in the earth＇s crust. The crustal velocity ratios （Vp/Vs） range from 1.70 to 1.79 with an average of 1.75,which is lower than the global average 1.78 of the continental crust. It may suggest that most of the earthts crust in the central and southern Mongolia lacks mafic component. In the northwest and southeast of the survey line, the Vp/Vs ratios are relatively high, which is likely related to the remanent femic Paleozoic crust or the magma underplating in the Cenozoic.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2014年第7期2386-2394,共9页
Chinese Journal of Geophysics
基金
科技部国际合作项目(2011DFB20210)资助
关键词
接收函数
蒙古中南部地区
H-κ叠加
CCP叠加
地壳厚度
波速比
Receiver function
Central and southern Mongolia
H-κ stacking method
CCPstacking method
Crust thickness
Vp/Vs ratio
