During the 2008 Iwate-Miyagi Nairiku Earthquake, long period ground motion with a period of three to four second is observed in Senboku plain, Miyagi prefecture, Japan. In this paper, to characterize these ground motions, following points are studied. At first, we compare these motions and past records those abound in the long-period component using Fourier spectra. Spectral amplitudes of these event motions are almost coincident with those of past records. And stability of peak frequency at K-NET MYG006 station is studied. The result shows that predominant frequency of each event is almost the same. Finally, propagation direction is studied. Results come from this study indicate that long period ground motion is comprised of surface wave excited by deep plain structure.
Journal of Japan Association for Earthquake Engineering 11 (5), 17-27, 2011
JAPAN ASSOCIATION FOR EARTHQUAKE ENGINEERING