楔形鄂霍次克板块的俯冲与被俯冲及其板内洋缘盆地演化的动力学研究

The Okhotsk plate is a wedge-shaped continental plate including some marginal basins. It consists of far eastern Siberia, most part of the Sea of Okhotsk, the entire Kamchatka, Sakhalin Island, and the Northern Japan regions. It contacts with the North American plate and the Philippine Sea Plate along the northern and southern strike-slip boundaries, respectively, and contacts with the Eurasian plate along the northern part of the western divengent boundaries. However, the Okhotsk plate faces to strongly subducting actions from the northwestern Pacific plate along the eastern boundaries of the Okhotsk plate while it subducts to Amurian plate from northern Sakhalin, along the eastern margin of the Japan Sea, to central Japan. The southwestern and eastern boundaries of the Okhotsk plate and its surrounding areas are thus the places continuously producing a lot of earthquakes, and huge earthquakes somtimes. In this study, we take full advantage of the geological and geophysical source of observational data accumulated by these years of researches, and establish three-dimensional models describing the Okhotsk lithospheric plate and the corresponding mechanisms. By using the finite element method in spatial and finite difference method in temporal, we study how the subducting processes related to the Okhotsk plate influence the intraplate deformations and stresses, and simulate the detailed formation and evolution processes of those marginal basins in the Okhotsk plate. We take the elastoplastic features of slabs along the eastern and western boundaries into account for the large rate of subduction case. We then explore the all the possible forces driving the Okhotsk plate motion and the evolution mechanisms forming these different marginal basins. This research can also help us to understand more about the formation mechanism of some earthquakes occurring in Northeastern Asia areas including the northeast China regions.

鄂霍次克板块是一个伴有数个洋缘盆地的楔形大陆板块，由远东西伯利亚、鄂霍次克海大部、整个勘察加半岛、以及萨哈林与北日本地区组成。它以走滑方式北接北美板块，南邻菲律宾海板块，东部边界受到来自西北太平洋板块的强烈俯冲，西部边界北段与欧亚板块以张性接触方式相邻，南段自萨哈林岛北端向南沿日本海东缘，接力俯冲到阿穆里亚板块下方，整个鄂霍次克板块的东西两侧边界及邻近地区，因此持续处于地震的多发与强发状态。 本研究利用逐渐累积的地质与地球物理来源的观测数据，通过构建鄂霍次克板块岩石层三维结构及力学模型，使用空间有限单元与时间有限差分方法，考虑该板块东西两侧俯冲带之大俯冲速率下的弹塑性特征，模拟鄂霍次克板内形变与应力场的时空变化以及板内不同洋缘盆地演化的差异特征，探索驱动其板块运动的各种力源及形成板内洋缘盆地的演化机理。该研究可以帮助我们加深理解发生于东北亚包括中国大陆东北地区一些地震的孕育与发生机理。

鄂霍次克海位居西太平洋一系列边缘海的最北部，是研究洋-陆俯冲以及洋缘盆地动力学演化的理想场所。采用数值模拟方法，探讨鄂霍次克海板块的俯冲及其板内洋缘盆地的开启和演化，对于我们获得该板块的运动驱动机制的新的认识，具有重要意义。.我们建立了一系列洋-陆俯冲带的二维数值模型，对地幔转换带内板块俯冲模式的分类，以及不同模式的动力学控制因素，进行了系统的探讨。模拟结果揭示了海洋俯冲板块在地幔转换带内的四种俯冲模式：褶皱型、穿越型、平躺型和回折型，其中以向前平躺型俯冲最为常见，褶皱型俯冲极少。俯冲海洋板块的年龄、上覆大陆岩石层的厚度以及板块汇聚速率对俯冲模式的控制作用至关重要，海洋板块的俯冲作用还影响了上覆大陆岩石层的变形行为，导致大陆岩石层的减薄效应。这些研究成果能为揭示华北克拉通减薄/破坏的动力学过程提供一定的理论参考依据。.俯冲启动是俯冲整个过程最开始且极为重要的一环，我们分别建立了倾斜型、弯曲型和垂直型分界面的数值模型，结果显示：倾斜型俯冲的俯冲角度最大，俯冲深度最深，海沟深度最深；垂直型俯冲的俯冲角度次之，俯冲深度最小，海沟深度仅次于倾斜型俯冲，显示俯冲板块的倾角与海沟深度呈正相关。.建立鄂霍次克海微板块的有限元模型，模拟研究该区域不同深度的三维速度场与应力场等并探讨其地球动力学意义。结果显示，鄂霍次克微板块下部的上地幔运动速率可能大于整体的板块速率，故而在其板块中间部分受到明显的拉张作用。.基于以前相关地球动力学研究的工作积累，我们还探讨了全球俯冲带地震各向异性及其机理，计算了鲜水河断裂带的地表热流并分析其地下水热结构，给出了最近5Ma年来全球古地磁场强度及变化年表，以及模拟研究了太平洋南部边界RRF型三联点附近地区的岩石层热结构等，获得并发表了一些很有意义的研究成果。