南海トラフ沿いの巨大地震による長周期 (約2〜20秒) 地震動の予測

概要

論文の詳細を見る
In this paper, a semi-empirical synthesis method is developed for statistically estimating longperiod (2 to 20 sec) surface waves during the mainshock from records for small events such as aftershocks. Normal mode theory and fault dislocation theory are used. In this method, the effect related to rupture propagation over the fault, the correction for radiation amplitudes of surface waves due to the difference in mechanisms between a mainshock and an aftershock, and the removal of ghostly oscillatory motions in the high frequency range, etc., can be considered. Ground motions for the mainshock are synthesized using aftershock records obtained by low-magnification seismographs of Central Meteorological Observatory for the Nankaido earthquake (Ms = 8.1) of December 20,1946. Long-period ground motions and acceleration response spectra with 2% critical damping are calculated at the sites of Kobe and Sumoto. The synthesized seismogram and response spectra are in good agreement with those calculated for the mainshock by Inoue et al. Under certain circumstances, horizontal components of the acceleration response spectra at Sumoto during a great earthquake along the Nankai trough may exceed the design spectra for the Honshu-Shikoku bridges. This synthesis method implies the possibility of prediction of long-period ground motions for future large earthquakes.
日本自然災害学会の論文
1986-03-31