報告書番号

380041

タイトル（和文）

原子力発電所等短周期構造物の耐震設計用地震入力の評価（その２基盤レベルでの強震地動スペクトルの近似予測手法）

タイトル（英文）

ESTIMATION ON EARTHQUAKE DESIGN INPUT TO SHORT PERIOD STRUCTURES SUCH AS NUCLEAR POWER PLANTS (2) -ON APPROXIMATE ESTIMATION OF SPECTRUM ON BEDROCK-

概要 （図表や脚注は「報告書全文」に掲載しております）

短周期領域（Ｔ＜１．０～２．０ｓｅｘ）の地震動特性に強い影響を与える断層運動のメカニズムは，破壊速度や断層面上の相対変位の非一様性や震源関数が時間の経過に対して滑らかに変化しない事による影響等，確率現象によって支配されていると考えられる。従って本報告では，このような確率現象を総合的定量的に評価し，断層運動にもとづいた，基礎レベルにおける加速度フーリェスペクトル振巾の予測手法について考察した。ここでは，基盤レベルにおける観測地動の，加速度フーリェスペクトルと単純な断層モデルによる理論フーリェスペクトルとの周波数領域の誤差Ｒ（ω）を実地震記録から求め，このＲ（ω）に２次の回帰曲線Ａ（Ｔ）をあてはめて係数ａを推定すると，Ｐａｋｆｉｅｌｄ地震では８，十勝沖地震で１，松代地震４であった。この時，係数ａは応力降下量くい違い速度に近似的に比例するように見える。

概要 （英文）

FOR THE EARTHQUAKE RESISTANT DESIGN OF STRUCTURES, IT IS VERY IMPORTANT TO ESTIMATE THE STRONG EARTHQUAKE GROUND MOTION SPECTRA. THE SIMPLE FAULT PROPAGATION MODEL,SUCH AS THE ONE SUGGESTED BY HASKEL(1969)HAS SUCCEEDED IN EXPLAINING THE FEATURES OF THE LONGPERIOD SEISMOGRAM)(T MORE THAN 1.0 SEC). HOWEVER,IT IS DIFFICULT TO EXPLAIN THE CHARACTERISTICS OF SHORT PERIOD SEISMOGRAM(ACCELEROGRAM;T LESS THAN 1.0 SEC)BY THE SIMPLE FAULT PROPAGATION MODEL MENTIONED ABOVE. IN THIS PAPER,THE VARIATION OF THE OBSERVED SPECTRUM IN THE SHORT PERIODRANGE IS ESTIMATED. THIS VARIATION IS DEFINED BY FS(OMEGA)AND B(OMEGA):WHERE FS(OMEGA)IS THE THEORETICAL ENVELOPE SPECTRUM ON THE BEDROCK. THE ATTENUATION EFFECT OF WAVE PATH IS CONSIDERED APPROXIMATELY. THUS THEVALUE OF R(OMEGA)GIVES AN INDICATION OF THE EFFECT OF SO-CALLED STICK-SLIP PHENOMENON ALONG THE FAULT PLANE. THE STRONG MOTION RECORDS USED FOR THIS STUDY ARE TOKACHI-OKI EARTHQUAKE(1968),PARKFIELD EARTHQUAKE(1966)AND MATSUSHIRO EARTHQUAKE SWARM(1966). TO DESCRIBE R(OMEGA),THE FUNCTION A(T)WITH COEFFICIENT A IS USED FOR REGRESSION EQUATION. FROM THE ANALYSIS OF THE ABOVE EARTHQUAKE RECORDS, THE COEFFICIENT A IS ESTIMATED AS FOLLOWS: A=1 FOR TOKACHI-OKI EARTHQUAKE A=8 FOR PARKFIELD EARTHQUAKE AND A=4 FOR MATSUSHIRO EARTHQUAKE SWARM, RESPECTIVELY. THE BIGGER THE COEFFICIENT A IS, THE SMALLER THE DIFFERENCE BETWEEN THE THEORETICAL AND THE OBSERVED SPECTRUM. SO IT MAY BE SAID THAT THE FAULT MOVEMENT FOR THE PARKFIELD EARTHQUAKE WAS SMOOTHER THAN THAT OF THE TOKACHI-OKI EARTHQUAKE, AND MATSUSHIRO EARTHQUAKE SWARM. THE FS(OMEGA)IS A KNOWN FACTOR AND R(OMEGA)IS ESTIMATED APPROXIMATELY BY THE FUNCTION A(T). USING THIS METHOD, THE SPECTRUM AT THE BEDROCK LEVEL IS APPROXIMATELY ESTIMATED.

報告者

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