Simplified Ground Modeling of Central Kochi City for Nankai Megathrust Earthquakes

2015 Fiscal Year Final Research Report

• Project/Area Number: 25420486
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Structural engineering/Earthquake engineering/Maintenance management engineering
• Research Institution: The University of Tokushima
• Principal Investigator: MIKAMI ATSUSHI 徳島大学, ソシオテクノサイエンス研究部, 准教授 (10262122)
• Co-Investigator(Renkei-kenkyūsha): SAITO Takehiko 北見工業大学, 工学部, 助教 (70646984)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 南海地震 / 高知 / 不整形地盤 / 微動 / H/Vスペクトル比

Outline of Final Research Achievements

The author proposes a method that combines microtremor measurement and a best-simplified ground model. This study applies the method to Kochi City. The author conducted microtremor measurements at approximately 70 stations in central Kochi and evaluated predominant frequencies. Referring base rock depths from boring, the central area of Kochi plain is modeled by a simplified approach. Eigenvalue analysis shows that 1st mode vibration predominates where deep soft soil sedimentation forms.
To improve the seismic source model, the authors collected about 310 actual accounts of ground shaking for the Showa-Tonankai Earthquake and about 350 accounts for the Showa-Nankai Earthquake to examine proposed fault models.
It was found that testimonies are closely consistent with the models for the Showa-Nankai Earthquake and Showa-Tonankai Earthquake. However, they are also partly inconsistent with the latter model regarding short-period seismic-wave source off-Mie prefecture.

Free Research Field

地震工学