The seismic ground motion records observed in the Kashiwazaki-Kariwa Nuclear Power Station were used to evaluate a regional three-dimensional velocity structure model that would be used for long-period ground motion prediction. First, the velocity structure model evaluated by the National Institute of Advanced Industrial Science and Technology was modified by incorporating the underground structure information obtained by geophysical exploration of the site and surrounding area. Next, the earthquake ground motions with a period of more than 2 seconds due to medium or small earthquakes occurred near the source regions of the huge scenario earthquake were simulated by the three-dimensional finite difference method. The effectiveness of the modified model was evaluated by the reproducibility of the waveforms and the response spectra.
In order to evaluate the variability of predicted ground motion amplitude due to aleatory uncertainty of the source parameters, we conducted ground motion simulation considering the uncertainty of the source parameters. Since the characteristics of the variability of simulated ground motion amplitude are consistent with the variability investigated by analysis of ground motion records (Hikita et al., 2018), the uncertainty of the fault parameters assumed in the simulation is reasonable. The characteristics of the variability of simulated ground motion amplitude varied according to the seismic magnitude. In the simulation for MJ7.0 earthquake, the variability of simulated ground motion amplitude of about 2 seconds in period was relatively large.
At first, it is confirmed that the damping ratio calculated by the strain energy proportional damping method is consistent with the damping ratio evaluated from the microtremor observation of the single column pier. Next, we evaluated the damping ratio of the various type of railway viaducts analytically and proposed the evaluation method of the damping ratio based on the amplitude ratio of underground part to entire structure which is calculated from the primary vibration mode shape. Furthermore, we proposed the evaluation method for seismic nonlinear response of railway viaducts by using the proposed evaluation method of the damping ratio. The nonlinear seismic response considering the proper damping ratio can be obtained by using this method, and the calculation procedure is almost the same as that by using the conventional method. Therefore, this method is effective for evaluating the seismic response of railway viaducts for the seismic design.
Governments estimate earthquake damage affected by only the main event of an earthquake. However, the damage is amplified by aftershocks and subsequent cyclic events. From the point of view of disaster protection where estimation of full extent of the damage is important in canceling evacuation order, we propose an evaluation method for degrading seismic resistance of wooden buildings exposed to cyclic events using seismic capacity grade. The object region is Ojiya City and the event is Niigata Prefecture Chuetsu Earthquake of 2004. It is revealed that the ratio of degrading seismic resistant performance is larger in large intensity, small seismic capacity grade buildings and that the probability of amplified damage is larger in large intensity. The proposed approach is applied to Sapporo City, and the number of damaged buildings, deaths and recovery cost with each correspondence after the main shock are simulated.
The seismic damage data of flat roads subjected to strong ground motions and liquefaction in the 2011 off the Pacific coast of Tohoku earthquake were analyzed and the fragility curves describing the probability of occurrence of a failure to flat roads were derived based on probabilistic modeling. Flat roads distributed in a seismically potential liquefied area have a risk to show the relatively higher value of damage-ratio index when PGV of 30 cm/s or instrumental seismic intensity, IJ of 5.0, that is the relatively lower value of seismic intensity.
As is the case with other natural phenomena such as seismic motions and tsunamis, the influence on the facilities by the permanent displacement of the ground is evaluated appropriately considering its uncertainty which is evaluated by hazard analysis. And, mitigation measures should be taken in accordance with the evaluation result. In this paper, trial analysis where fault displacement is input at the lower surface of the base slab of a PWR type reactor building is performed. In this analysis, structural safety is assessed by using nonlinear finite element models of reinforced concrete members such as the base slab of the reactor building.
A revised empirical relation formula (Okawa et al., 2013) that can calculate seismic ground motions is adopted by Ministry of Land, Infrastructure, Transport and Tourism, as the method to evaluate the long-period ground motions for Nankai Trough earthquake. The authors conducted parametric study about the influence of the selection of the fault model and the site-specific amplification, which are dominant parameters of the method, and compared the calculations to observations and prepared waveforms using revised empirical relation formula. Then, we evaluated the application range and discussed cautionary notes when using this method.
The damage factor of small earth dam for irrigation on the 1983 Middle Japan Sea Earthquake in Aomori prefecture was revalidated by the geographical information system (GIS) using the damage situation of small earth dam for irrigation at that time, the assumed seismic intensity distribution map, the topography and geotechnical condition of surrounding area, the embankment material, the foundation ground material and the small earth dam for irrigation ledger, etc. As a result, the damage factor of small earth dam for irrigation on the 1983 Middle Japan Sea Earthquake is considered to be attribute to the constituent materials of embankment and foundation ground. Especially, the damage occurrence rate of small earth dam for irrigation with sandy soil materials is high, and it is due to the influence of liquefaction in sandy soil materials.