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

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 14540397
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 固体地球物理学
• Research Institution: KYUSHU UNIVERSITY
• Principal Investigator: YOSHIOKA Shoichi Kyushu University, Faculty of Sciences, Associate Professor, 大学院・理学研究院, 助教授 (20222391)
• Project Period (FY): 2002 – 2004
• Keywords: Philippine Sea plate / simulation of temperature and flow / interplate large earthquake

Research Abstract

1.Development and modeling of 3-D source code of temperature and flow
Based 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 deformation
We 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.