中-下地幔散射体:探测方法、研究进展和展望  

Mid-lower mantle scatterers:Detection methods,research progress and prospect

作　　者：李娟[1,2,5] 陈思丹 何小波 王巍 杨凡 Li Juan;Chen Sidan;He Xiaobo;Wang Wei;Yang Fan(Key Laboratory of Earth and Planetary Physics,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Department of Ocean Exploration and Technology,Zhejiang Ocean University,Zhoushan 316022,China;Department of Earth Sciences,University of Southern California,Los Angeles,CA 90007,USA;Heilongjiang Mohe Observatory of Geophysics,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]中国科学院地质与地球物理研究所地球与行星物理院重点实验室,北京100029 [2]中国科学院大学地球与行星科学学院,北京100049 [3]浙江海洋大学海洋科学与技术学院海洋探测与技术系,舟山316022 [4]美国南加州大学地球科学系,洛杉矶900075 [5]黑龙江漠河地球物理国家野外科学观测研究站,中国科学院地质与地球物理研究所,北京100029

出　　处：《地球与行星物理论评（中英文）》2023年第3期339-354,共16页Reviews of Geophysics and Planetary Physics

基　　金：国家自然科学基金资助项目(42074063);中国科学院地质与地球物理研究所重点部署资助项目(IGGCAS-201904)。

摘　　要：得益于地震波传播理论的快速发展、数据分析方法日新月异的变化以及地震观测覆盖区域的增加,我们对地球深部的探测能力从原有的百千米尺度提升到目前的千米尺度.地震层析成像研究很早就揭示出体积庞大的下地幔存在数千千米尺度的不均匀体,而对下地幔更小尺度上(约十千米至百千米)的认识则来自于基于台阵分析的高频地震散射波探测技术.大量证据表明整个下地幔分布着数千米至数千千米不同尺度的速度不均匀体,其形成可能与俯冲至下地幔的洋壳和俯冲板片的岩石圈地幔物质密切相关.因此,对下地幔不均匀体的探测及其分布规律和形成机理的认识,将有助于理解地球内部物质构成及其矿物相变、热化学结构等,进而深化我们对地幔流变性、地幔对流模式和地幔混合效率等地球内部热化学、动力学过程的认识.本文聚焦于分布在约700~2000 km中-下地幔深度的小尺度不均匀体/散射体,首先从散射体的定义和小尺度不均匀性的统计学描述出发,分别介绍探测下地幔小尺度散射体的地震波“探针”及探测方法的特点和局限性,简要回顾一些代表性研究;其后基于搜集到的200余个下地幔散射体数据,分析统计了散射体的深度分布特点;最后针对下地幔散射体探测方法中的问题给出思考,并对该研究方向进行了展望.Thanks to the rapid development of seismic wave propagation theory,emerging of data analyzing methods,and the increasing coverage of the seismic exploration,our ability to probe deep into the Earth has been increased from the scale of 100 kilometers to the scale of kilometers at present.The existence and wide-distributed heterogeneities at a scale of thousands of kilometers in the massive lower mantle have been revealed by seismic tomography for a long time,while the knowledge of smaller scales(~10~100 km)has come from high-frequency seismic scattered wave detection techniques that are mainly based on array analysis.A growing body of evidence shows that multiple-scale heterogeneities distribute through the Earth's entire lower mantle;the heterogeneities have been attributed to basaltic oceanic crust and its underlying lithospheric mantle.Therefore,detecting and characterizing of their distribution and formation mechanism will help understand the material composition,mineral phase transformation,and thermochemical structure of the Earth's interior.Furthermore,they shed light on the thermochemical and dynamic processes of the Earth's interior,such as mantle rheology,convection,and mixing efficiency.This review focuses on the small-scale heterogeneities/scatterers distributed in the mid-lower mantle at a depth of~700~2000 km.Firstly,from the perspective of the definition of the scatterers and statistical description of small-scale heterogeneities,we introduce a variety of seismic waves,acting as the"probes"for the small-scale heterogeneities in the lower mantle,and then summarize the characteristics and limitations of available detection methods.Moreover,some representative studies are briefly reviewed.Based on the data of more than 200 lower mantle scatterers collected from previous publications,we characterize the distribution of scatterer's depths.Finally,we point out some unsolved problems in the detection method of lower mantle scatterers and propose the prospect for future research directions.

关 键 词：中-下地幔 散射体 台阵技术 地震波探针 不均一性 

分 类 号：P315[天文地球—地震学]