Automatic detection of multiple solutions of stress tensor inversion from fault-slip data and stress states around subduction plate boundary

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K17776
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geology
• Research Institution: Kyoto University
• Principal Investigator: Sato Katsushi 京都大学, 理学研究科, 助教 (70509942)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 応力逆解析 / 小断層解析 / 混合確率分布 / 底付け付加体 / 構造性メランジュ

Outline of Final Research Achievements

A new method of stress tensor inversion was developed to automatically detect multiple stress states from heterogeneous fault-slip data. The method determines the number of stresses by Bayesian information criterion with mixture probability distribution in the deviatoric stress space. Firstly, the method was applied to faults cutting Quaternary sediments around the Beppu bay area, SW Japan and successfully detected a change in the orientation of tensional stress axes around 1 Ma. Secondly, faults in a tectonic melange in the Cretaceous to Paleogene Shimanto Belt were analyzed. The detected stresses were interpreted as normal-faulting stress states just under the subduction plate boundary. Additionally, a computerized method to determine frictional coefficient from the orientation distribution of fault planes was developed. It was applied to the faults in the melange and extremely low friction coefficients (0.1-0.2) were obtained.

Free Research Field

構造地質学