報告書番号

N05010

タイトル（和文）

地震観測記録に基づく地震動の減衰特性（その２） -強震時の減衰特性を考慮した等価線形解析による上下動評価法の提案-

タイトル（英文）

Attenuation characteristics of seismic motion based on earthquake observation records Part2. Proposal of new equivalent linear analysis technique considering attenuation characteristics during strong motion for precise vertical motion simulation

概要 （図表や脚注は「報告書全文」に掲載しております）

本研究では，水平動と上下動の同時入力による等価線形解析を用いた強震時の上下動のより詳細な評価を目的として，Qp-1を考慮するための複素体積弾性率を導入した等価線形解析手法を提案した．提案する手法では，従来の等価線形解析手法に対して次の点を新たに導入した．・ポアソン比を定義せず複素体積弾性率を導入し，複素体積弾性率は強震時と弱震時で一定とする．・減衰を材料減衰と周波数依存項(散乱減衰)の総和で定義し，周波数依存項は強震時と弱震時で一定とする．提案手法を兵庫県南部地震の強震記録に対して適用した結果，上下動に影響を及ぼすP波速度およびQp-1が強震時にもほとんど変化していないことが分かった．また，従来の手法よりも明らかに観測値を再現しており，より詳細に上下動を評価する目的において高い性能を有することが示された．

概要 （英文）

In this report, we proposed new equivalent linear analysis technique introducing complex bulk modulus to consider Qp-1 because it was necessary to evaluate vertical motion more precisely during large earthquake by equivalent linear analysis using the input of the horizontal and the vertical motion simultaneously. In the proposed technique, following points were newly introduced into equivalent linear analysis technique.・Complex bulk modulus is introduced without Poisson’s ratio, and complex bulk modulus is assumed to be constant under strong and weak earthquake motion.・Damping factor is defined by the sum of the material damping and the frequency dependence damping (scattering attenuation), and the frequency dependence damping factor is assumed to be constant under strong and weak earthquake motion.The proposed technique was applied to strong motion simulation during 1995 Hyogo-ken-nanbu earthquake for demonstrating high performance of this technique. From the analytical result, P-wave velocity and Qp-1 that mainly influenced vertical motion simulation has hardly changed during strong motion same as well as actual phenomena derived strong motion observation records. Moreover, it was demonstrated that proposed technique was in more good agreement with the observations than present technique. Therefore proposed technique has a high performance in the purpose to evaluate the vertical motion more precisely.

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