統計的グリーン関数による想定東南海地震の広帯域強震動予測と建物被害予測

Abstract

我々は, 想定東南海地震について, まず不均質震源モデルと広周波数帯域統計的グリーン関数法を用いて, 定量的強震動予測を行ったところ、過去の地震の推定震度を再現でき, 既往の研究結果や経験的距離減衰式とよく対応する予測波形を得た。次に非線形応答解析モデルにこの予測強震動を入力して, 近畿・中部地域における建物群の被害予測を行ったところ, 想定東南海地震震源域から近い所や海岸地域と川沿いの沖積地盤地域などの比較的地盤が軟らかいところでは建物種別を問わず, 大破以上の被害を受けるという予測結果となった。建物構造種別でみると低層鉄骨造建物, 木造建物, 中低層RC造建物の順に被害率が小さくなることが分かった。

We used an empirical Green's function method together with the randomly perturbed asperity source to sum up broadband statistical Green's functions for a moderate size earthquake to predict strong ground motions due to the expected Tonankai earthquake. We were able to simulate seismic intensity distribution similar to past earthquakes and strong motion waveforms that correspond to previous studies and attenuation relations. Using these results, we predicted building damage by non-linear response analysis and found that at the regions close to the source as well as regions with relatively thick soft sediments such as the shoreline and alluvium deposits along the rivers, there is a possibility of severe or higher damage regardless of the type of buildings. Also, damage ratio for buildings built before 1981 was higher than those built after and the damage ratio was highest for steel buildings, followed by wooden buildings and then reinforced concrete buildings.