東海・東南海・南海連動地震の長周期地震動シミュレーション
関東・濃尾・大阪平野における長周期地震動予測
本研究では，関東，濃尾，大阪平野を含む3次元地盤モデルを用いて，東海・東南海・南海連動地震の長周期地震動シミュレーションを実施した。震源モデルは中央防災会議のものをベースとし，震源の再分割や滑り分布と破壊伝播時刻の不均質性を付加した。また，破壊開始点の影響や，連動地震に対する単独地震の寄与についても検討した。
その結果，此花で5〜6秒と7〜8秒，名古屋で3.5秒，新宿で8秒付近に中心周期を持つ地震動が計算され，いずれも告示スペクトルを上回った。また，南海地震が南西側から破壊する場合，大阪平野のみならず，遠方の濃尾平野や関東平野において10秒以上の周期帯の地震動にも大きな影響を与えることがわかった。
| キーワード： | 長周期地震動，東海地震，東南海地震，南海地震，3次元FEM |
＊１ 技術センター 建築技術研究所 防災研究室
＊２ 技術センター 技術企画部 情報技術室
Long-period Ground Motion Simulation of Tokai-Tonankai-Nankai Coupled Earthquake
Prediction of Long-period Ground Motion Considering the Kanto, Nobi, and Osaka Basins
We conducted a long period ground motion simulation of Tokai-Tonankai-Nankai coupled earthquake considering 3D subsurface ground model including Kanto, Nobi and Osaka plain. We constructed the source model based on the one proposed by the Central Disaster Prevention Council, Cabinet Office of Japanese government and introduced the heterogeneity into slip distribution and rupture propagation. We studied the influence of the location of rupture starting point and the contribution of each earthquake to the estimation results of coupled earthquake.
The results showed that the pseudo velocity response spectra at Konohana in Osaka plain have a significant peak around 7 to 8 seconds, and those of Nagoya in Nobi plain have a peak with the period of 3.5 seconds, and those of Shinjuku in Kanto plain have a peak at around 8.5 to 9 seconds. These peaks of pseudo velocity response spectra surpassed the uniform design spectra regulated by Building Standard Law. It was found that the Nankai earthquake amplified the long period ground motions over 10 seconds in Nobi and Kanto Plain when the rupture started from the south east point of the fault plain.
| Keywords: | long period ground motion, Tokai earthquake, Tonankai earthquake, Nankai earthquake, 3D FEM |
*1 Disaster Prevention Research Section, Building Engineering Research Institute, Technology Center
*2 Information Technology Section, Technology Planning Department, Technology Center
