基于程函方程与三维速度模型的中国东北地区地幔过渡带接收函数研究  

Mantle transition zone beneath northeast China imaged by receiver function data using fast marching eikonal solver based 3-D migration

作　　者：张炎 钮凤林[2,3] 宁杰远 ZHANG Yan;NIU FengLin;NING JieYuan(School of Earth and Space Sciences,Peking University,Beijing 100871,China;Department of Earth,Environmental and Planetary Sciences,Rice University,Houston 77005,USA;State Key Laboratory of Petroleum Resource and Prospecting,and Unconventional Natural Gas Institute,China University of Petroleum,Beijing 102249,China;Hongshan National Observatory on Thick Sediments and Seismic Hazards,Beijing 100871,China)

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]美国莱斯大学地球、环境与行星科学系,休斯顿770053 [3]中国石油大学石油资源与勘探国家重点实验室和非常规天然气研究所,北京102249 [4]河北红山巨厚沉积与地震灾害国家野外科学观测研究站,北京100871

出　　处：《地球物理学报》2022年第8期2945-2959,共15页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41874071)资助.

摘　　要：本文利用中国东北地区NECESSArray记录到的45505条接收函数,结合该区域最新三维速度模型,采用快速行进法求解程函方程,计算了P-S转换波相对走时,并通过共转换点叠加成像方法获得了该地区下方地幔间断面起伏情况.结果显示,在长白山—五大连池连线一带东西约300 km,南北约900 km的狭长形区域内,660-km间断面下陷幅度达20~40 km.其结构可细分为南北两部分,南部更为狭窄且与日本海沟走向一致,对应于从日本海沟俯冲的太平洋板块在地幔过渡带的滞留区;北部对应于从千岛海沟俯冲的太平洋板块在地幔过渡带的滞留区.同时,在长白山西部,存在与长白山—五大连池下陷区形状类似的南北向狭长形抬升区,660-km间断面抬升幅度约为10 km,显示俯冲太平洋板块只延伸至松辽盆地东侧;而在盆地西侧,660-km间断面的下陷区可能与该地区岩石圈拆沉有关.同时,410-km间断面在松辽盆地—渤海一带,以及长白山火山西南和东北方向存在明显的下陷区;另外,在阿巴嘎及阿尔山也有小范围的下陷区.所有这些下陷区,均与地表新生代火山活动区/拉伸区有很好的对应关系,表明这些地表构造与深部热物质上涌有关.In this study,we utilized 45505 teleseismic receiver functions derived from NECESSArray records to image the mantle transition zone beneath northeast China.We employed a fast-marching technique to solve the eikonal equations of the direct P wave and P-to-S converted waves in a 3-D velocity model.We selected the high-resolution 3-D model of FWEA18 that was derived from full waveform inversion as the reference velocity model.We gathered the receiver functions based on their geographical locations and stacked the receiver functions with a common conversion point(CCP).We found clear P-to-S conversion associated with the 410-km and 660-km discontinuities that define,respectively,the upper and lower boundaries of the mantle transition zone.The 660-km discontinuity deepens by 20~40 km in a~300 km by~900 km elongated area extending roughly in the north-south(NS)direction beneath the Changbaishan-Wudalianchi area.The southern and northern parts of the depression area show a distinct difference that suggests that the Pacific plate subducted from the Japan and Kuril trenches has different morphology when it encounters the upper and lower mantle boundary.The western front of the trough lies a N-S oriented uplift area with an elevation of~10 km.These observations suggest that the subducted Pacific oceanic lithosphere only reaches to the eastern side of the Songliao Basin.We also observe a mild depression of 660-km beneath the Great Xing′An Range west to the Songliao Basin,which is likely caused by a delaminated continental lithosphere.Overall,the 410-km discontinuity appears to be flatter than the 660-km.It deepens slightly beneath the Songliao Basin,Bohai,the southwest and northeast sides of the Changbaishan volcano,the Abaga and Arshan volcanic regions.These depressions correspond well with extensional and volcanic regions,suggesting magmatism in the study area is largely controlled by ascending hot material from great depths.

关 键 词：中国东北 接收函数 地幔过渡带 新生代火山 俯冲带 

分 类 号：P315[天文地球—地震学] P541[天文地球—固体地球物理学]