俯冲带类型对海山俯冲动力学的影响

In the past 20 years, multidisciplinary subduction zone initiatives worldwide have revealed the variability of subduction zones, and identified the significant differences in the tectonic structure and kinetics of the two basic types, accretionary and erosional subduction zones. The accretionary subduction zone is associated with relatively low subduction angle, young subducting plate, and thin subduction sediment and subduction channel, as well as notable accretionary wedge structure, while the erosional subduction zone is the antipode. The accretionary subduction zone also shows larger background stress with greater earthquake magnitude, in contrast to the erosional subduction zone..Seamounts are topographic anomalies widely distributed in the ocean. The subduction of seamounts has notable influence on the morphologic evolution, material transportation, and seismic activities of subduction zones. The seamount subduction is thus of great significance to understand global tectonics and crust-mantle material circulation. Seamout subduction dynamics are expected to highly depend on the subduction zone type and corresponding tectonic structure, but this influence lacks systematic quantification..This project is aimed to quantify the influence of subduction zone type (i.e., accretionary versus erosional) on the seamount subduction. This project will construct three-dimensional viscoplastic models to simulate the dynamic evolution of seamounts during their subduction. Using identified subducted seamounts and seismic observations in the Western Pacific, South China Sea, and Indian Oceans, the relationship between subducted seamount and local seismicity, as well as seamount subduction depth, will be derived. By comparing these observations and modeling results, this project will systematically study the effects of subduction zone type on seamount subduction dynamics, and identify the key factors that control the seamount subduction depth and seamount-seismicity relationship.

近20年全世界范围内的多学科俯冲带研究项目揭示了俯冲带的多样性，确定了俯冲带增生型和侵蚀型两种基本类型结构和动力学特征的显著差异。其中增生型俯冲带的俯冲角度和俯冲板块年龄较小，俯冲隧道较厚，存在增生楔结构，背景应力和地震震级较大，而侵蚀型俯冲带则相反。.海山是大洋中广泛分布的地形异常。海山俯冲对俯冲带地形地貌、物质循环和发震规律有不可忽视的影响，相关研究对于理解全球板块构造演化和壳幔物质循环等基本科学问题有重要意义。海山俯冲的动力学过程必然受到俯冲带类型的影响，但该影响缺乏系统的定量研究。.本项目拟以西太平洋-南海-印度洋这"两洋一海"的海山俯冲实例和地震观测为基础，以增生和侵蚀两种类型俯冲带的海山俯冲深度和海山-地震相关性为约束，利用三维粘塑性地球动力学模型模拟俯冲海山的应力应变演化，揭示控制海山俯冲深度以及海山-地震相关性的关键因素，系统地研究俯冲带从增生型到侵蚀型对海山俯冲的影响。

海山俯冲对俯冲带地形地貌、物质循环和发震规律有着深刻的影响；同时，海山自身的形变和俯冲深度也受到俯冲上板块的影响。本课题结合地球物理数据、数值模拟和物理模拟，研究了海山俯冲和上板块相互作用的动力学过程，并分析了海山俯冲对俯冲带地震的影响。本项目主要取得以下成果：1) 总结了海山俯冲的实例及其与俯冲带地震之间的关系；2) 用数值模拟研究了三维俯冲海山对上板块形变和应力的影响,以及俯冲海山自身形态和应力状态的变化；3) 用物理模拟研究了海山俯冲过程中海山自身的形变。本项目结合数据和模型系统的研究了俯冲海山和俯冲带相互作用的机制，揭示了不同俯冲带类型对海山俯冲的影响，有助于进一步认清海山俯冲对俯冲带物质循环和地震的影响，增进对俯冲带动力学和地震动力学的理解、以及为地震和海啸灾害预防提供理论基础。