利用ScS多次波探测东北亚海域及陆缘地幔间断面特征

Northeast Asia is one of the ideal locations to study the deep mantle structure and the mantle dynamic processes associated to northwest Pacific subduction. This project will focus on the characteristics of upper mantle discontinuities beneath the vast sea and continental margin regions in NE-Asia. We will develop and improve the method of using long-period multiple-ScS reverberations to image the fine-scale structure of mantle discontinuities; we will apply the improved method to the ScS reverberation groups recorded by the “Chinese Digital Scismic Network” and the temporal seismic array stations installed in northeast China, which sample regions with little/no seismic instrumentation installed, and map the detailed undulation of the upper mantle discontinuities beneath; we will integrate recent progresses obtained from seismic tomographic images and receiver function analysis to discuss the thermal and/or chemical abnormal related with the discovered structure. We hope this study will make it possible in future to construct a complete, integrate and clear picture covering the whole region from sea, continental margin to the continents, which will definitely provide significant insights into the understanding of material differentiation and energy exchange process during different stages of mantle circulation...This project is expected to contribute to the major program of “China Geophysical Reference Model” (CGRM). Our objective to image the undulation of upper mantle discontinuities beneath sea region and continental margins in NE-Asia is consistent with the mission of the ongoing major program and constitute one important part of the CGRM. We will provide the original data source and related models to the NSFC arrangement center of CGRM program when our project is completed.

东北亚地区是研究地幔深部结构以及与西北太平洋俯冲相关的地幔动力学过程的最佳场所。本项目将聚焦于台站稀少的东北亚海域和陆缘地区上地幔间断面结构研究。发展利用长周期ScS多次反射波获取较高分辨率的地幔间断面深度起伏的方法；利用“中国数字地震观测网络”和流动地震台阵记录到的西北太平洋俯冲带中深源地震ScS多次反射波数据，获取无台站分布的东北亚广大海域及陆缘地区地幔间断面深度起伏特征；在西北太平洋俯冲动力学背景下，探讨地幔间断面起伏的热或物质异常原因；为获取海域-陆缘-大陆完整的地幔间断面起伏图像，系统对比、全面认识在不同的俯冲阶段，俯冲板片和深部地幔物质的相互作用创造可能。. 本申请希望成为组建“中国区域地震学参考模型”的基金项目之一。研究内容“东北亚海域和陆缘地幔间断面特征”和“地震学参考模型”相符，在结题时保证为“参考模型”成果中心提供基金研究相关的原始地震资料和地震学模型。

东北亚地区是研究地幔深部结构以及与西北太平洋板块俯冲相关的地幔动力学过程的最佳场所。项目聚焦于台站稀少的东北亚海域和陆缘地区上地幔间断面结构研究。发展和改进了利用长周期ScS 多次反射波获取较高分辨率地幔间断面深度起伏特征的新方法，获得了包括鄂霍茨克海、千岛群岛、日本海、菲律宾海区域及陆缘等台站稀疏地区地幔间断面深度起伏特征。同时结合传统方法得到了西北太平洋俯冲地区从海域-陆缘-大陆的410-km和660-km间断面深度起伏，约束了板片停滞背景下大地幔楔的地幔流动模式、板片内部的应力分布状态，发现了地幔转换带上覆低速层的广泛存在。建立了板块从开始俯冲，到倾斜俯冲、停滞等不同阶段，地幔间断面对俯冲作用的响应图像，为认识东亚地区俯冲动力学模式、太平洋板块俯冲对地幔物质的影响和改造提供了系统、完整的地球物理观测证据，同时也为定量认识地幔热状态、地幔矿物组成，俯冲板片的命运以及水的赋存状态等重要科学问题给出了新的关键约束。