| 講演要旨(和文) | | 歴史地震の震源像を調べるために震度や住家被害率の分布を利用することは有効な手段である．本研究では，震度と常時微動H/Vスペクトル比の卓越周期の関係に基づき，表層地盤の影響を考慮して震度分布を再評価する手法を提案し，1891年濃尾地震に適用した．その結果，濃尾平野および地表地震断層が生じた周辺地域において，震度7の地点は，(1)およそ0.4秒から0.8秒の卓越周期(第II種・第III種地盤)をもち，地盤増幅によって震度が7になったと考えられる地点と，(2)卓越周期がおよそ0.4秒以下(第I種地盤)の地点とに切り分けられた．このことは，微動H/Vスペクトル比を用いて震度分布を再評価する手法の有効性を示していると考えられる．また，地盤条件が相対的に良好な震度7の地点は従来の伏在断層の北側寄りに分布し，強震動シミュレーションの結果からは濃尾地震時にこの区間が破壊したことが示唆される． |
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| | 講演要旨(英文) | | Applying the seismic intensities and damage ratio of wooden houses is useful for investigating the source image of historical earthquakes without strong ground motion records. In this study, we propose a method to evaluate a distribution of seismic intensities of historical earthquake by using the H/V spectral ratio of microtremors and apply to the 1891 Nobi earthquake. Here, we evaluate seismic intensities at 43 microtremor-measurement stations in the Nobi Plain and near the surface earthquake faults based on the relationship between seismic intensities and the predominant periods of H/V spectral ratio of microtremors. As a result, we classify the stations with the seismic intensity of 7 into two groups: (1) the stations which have the predominant period between approximately 0.4 sec and 0.8 sec, and (2) those have the predominant period of less than approximately 0.4 sec. Seismic intensities of 7 could be generated by the effect of rupture of a causative fault at the stations with the predominant period of less than 0.4 sec. We also demonstrate that the northern part of the Gifu-Ichinomiya Line ruptured as one of the causative faults during the 1891 Nobi earthquake through the strong ground-motion simulations. |
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