フィリピン海スラブの沈み込みに伴う温度・速度構造とスラブ内地震・地表変形の地域性

1.在二维温度流动有限差分源代码的基础上，完成了三维矩形平行六面体模型的有限差分源代码。我们对参数进行了无量纲化处理，对源代码进行了并行化处理，提高了源代码的运行速度，并开发了计算结果的可视化工具。利用源代码，考虑菲律宾海板块过去的俯冲史、斜向俯冲以及与吉南海山链走向距离不同而产生的温度边界条件，构建了日本西南部三维温度流俯冲模型。通过与实测热流数据的比较，提出了菲律宾海俯冲板块上表面新的温度分布，并成功地估计了托南开地震和南开地震的发震带。通过GPS数据的反演分析，揭示了Hyuganada地区板块间耦合与九州地区地壳变形的关系。结果表明，除了Hyuganada地区的板块间耦合作用外，九州地区的地壳变形主要表现为别府-岛原地堑深部的右向运动和东南向的地幔拖曳作用，这可能是冲绳海槽下地幔柱水平流动引起的。此外，我们从GPS数据反演中估计了四国的板间耦合。并估计了1968年Hyuganada （M7.5）地震和1946年南开（M8.1）地震的同震滑动区与本工程获得的板间耦合空间分布及其重复时间的关系。

1.Development and modeling of 3-D source code of temperature and flowBased on 2D finite-difference source code of temperature and flow, we completed finite-difference source code of a 3D rectangular parallelepiped model. We non-dimensionalized parameters, parallelized and made the source code faster, and developed visualization tools for calculated results. Using the source code, we constructed 3D subduction model of temperature and flow in southwest Japan, taking account of past subducting history of the Philippine Sea plate, oblique subduction, and different temperature boundary conditions due to difference in distance from the strike of the Kinan seamount chain. Comparing observed heat flow data with calculated ones, we proposed new temperature distribution on the upper surface of the subducting Philippine Sea plate, and succeeded in estimation of seismogenic zone of the Tonankai and the Nankai earthquakes.2.Estimation of interplate coupling off Shikoku to off east Kyushu and examination of regional difference in Earth's surface deformationWe revealed relation between interplate coupling in Hyuganada region and crustal deformation in Kyushu region from an inversion analysis of GPS data. As a result, we found that crustal deformation in Kyushu can be characterized by right-lateral motion at a deeper portion of the Beppu-Shimabara graben and southeastward mantle drag, which would be caused by horizontal flow of mantle plume which is produced under the Okinawa trough, in addition to interplate coupling in the Hyuganada region. Moreover, we estimated interplate coupling off Shikoku from GPS data inversion. We also estimated relation between coseismic slipped region associated with the 1968 Hyuganada (M7.5) and the 1946 Nankai (M8.1) earthquakes and spatial distribution of interplate coupling obtained in this project, and recurrence time of these earthquakes.