Earthquake cycle simulation in heterogeneous medium by XBIEM

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K04009
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: The University of Tokyo
• Principal Investigator: Kame Nobuki 東京大学, 地震研究所, 准教授 (90304724)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 地震サイクルシミュレーション / 境界積分方程式法 / 不均質構造 / 断層 / XBIEM

Outline of Final Research Achievements

To investigate the effect of structural heterogeneity, which is characteristic of subduction zones called accretionary structures, on the stress loading process of earthquake occurrence, a simplified "triangular accretionary zone model" is considered and a numerical code is developed to calculate elastic deformation using the extended boundary integral equation method (XBIEM). Backslip was applied in the sticking zone and the stiffness contrast between the upper accretionary zone and the lower plate was systematically varied to numerically analyze the distribution of backslip in the upper and lower plates, the magnitude of submarine crustal deformation, and quantitative changes in the plate boundary stress loadings. The results show that the stress field decreases in shear stress without changing the spatial distribution, and that the presence of low-stiffness accretionary zone structures lowers the stress loading rate of the seismic cycle.

Free Research Field

地震学

Academic Significance and Societal Importance of the Research Achievements

高度化する地震観測研究は、地下の「構造不均質」と「断層形状」ついて明かにしつつあるが、「地震発生前の応力場」の直接測定は未だ困難な問題として残る。本研究では、地震発生の理論的研究から応力場のヒントを探る。すなわち、構造不均質を含む地震発生サイクルモデルを用いて、構造不均質に起因する応力場が地震の動的破壊を規定し得るか調べた。本研究が更に発展し、地震開始/停止の位置と構造不均質との関係が理論的に示されたならはば、強震動予測における想定シナリオ地震の断層モデルパラメタ (現在、不確定性が非常に大きい) に強い拘束を与えることができる。より正確な予測は地震減災と直接結びつき、社会への影響も大きい。