地震後復旧活動計画のための確率論的余震発生モデルと余震ハザード評価の提案

摘要

After a large earthquake, aftershocks occur subsequently in a wide region, as were seen in the 2011 Tohoku earthquake. Those aftershocks cause secondary damage or delay of restoration activity. In addition, it is reported that there were the region where intensity of shaking due to aftershocks were bigger than that due to a main shock in some past earthquakes. Therefore, it is necessary to take account of the seismic risk due to aftershocks, too. In this study, using aftershocks data obtained in the events of the 2011 Tohoku earthquake and of other historical laige earthquakes, the spatial and temporal distribution of aftershock: occurrence is investigated and modeled based on the Gutenberg-Richter law and the Modified Omori's law. Then, a probabilistic aftershock occurrence model to predict the aftershocks of future large earthquakes is proposed, which is expected to be useful for development of restoration activity plan after future large earthquakes.%2011年東北地方太平洋沖地震を含む海溝型巨大地震による確率論的余震発生モデルのパラメータを提案し、パラメータによる感度解析及び短期間(0～10日間）と中期間(10～30日）の余震ハザード解析を行った.東北地方太平洋沖地震の余震による余震ハザードと観測値の比較によりパラメータの地震間誤差の考慮が必要であること、感度解析によって提案したパラメータの中でb(90)値,log_(10)N値,D_1値の影響が大きい一方、p値の影響は小さいこと、また本震発生から10日までの短期間の余震ハザードと10～30日間の中期間の余震ハザードの比較により、中期間の余震ハザードは短期間に比べ十分小さいことを示した.最後に適用例として、提案モデルを1923年関東地震と1854年安政地震に適用してその余震ハザード評価結果を示した.