Abstract
We conducted Normalized Input-Output Minimization (NIOM) method for the long-term earthquake observation records at Nagara Dam operated by the Japan Water Agency, and estimated the propagation time of the seismic waves and dynamic soil properties of the dam body. We compared our results with those in the detailed report by Sasaki et al. on the records of the 1987 Chiba-ken Toho-oki earthquake. These examinations revealed that (1) the P- and S-wave propagation times observed during the Chiba-ken Toho-oki earthquake and its aftershocks showed larger values than those observed after these earthquakes; (2) the temporal variation of the propagation times is quite small after the mainshock and aftershocks of the Chiba-ken Toho-oki earthquake; (3) the effects due to the 2011 Off the Pacific Coast of Tohoku Earthquake could not be seen in the dynamic soil properties of the dam body obtained in this study.
