This study examines the accuracy of damage estimation on region mesh units by fragility curves, and the damage evaluation method of wooden houses using the basic survey of city planning data. To examine the accuracy using fragility curves, this study compares the results of damage estimation by the Nankai Trough earthquake targeting Toyohashi city between two cases; one is the case in which the average rate of wooden housed by age is applied to all the regional meshes in Toyohashi city from the housing and land survey data of Japan, and the other one is the case in which the actual distribution of wooden houses by age is applied to each regional mesh from the basic survey of city planning data. To evaluate the damage to wooden houses, the damage probability curve is calculated by incremental dynamic analysis using strong ground motion records that are selected from the K-NET and KiK-net database. And the damage evaluation of wooden houses in Toyohashi city by Nankai trough earthquake is evaluated using the damage probability curve and the basic survey of city planning data. As a result, damage estimation results reflecting actual building distribution represent the actual damage situation better than damage estimation results using the average rate of wooden houses. In addition, it is shown differences in damage by building within the same regional mesh on the map in the case of the Nankai Trough earthquake.

The Empirical Green's Function Method (hereinafter referred to as EGF) is a widely used method with many achievements in the reproduction of seismic ground motions of past earthquakes. However, there are no clear criteria for selecting elemental earthquakes, and in particular, the effects of rupture propagation effects have not been fully considered. In this study, we analyzed the observation records of the 2004 Mid Niigata Prefecture Earthquake in the main-shock and aftershocks as an earthquake whose source destruction process of about M6 is clear. As a result, it was found that in the engineeringly major frequency band of about 1 Hz, there is a difference of about two times in the Fourier amplitude spectra on the forward side and backward side due to the influence of the fracture propagation effect. Next, waveform synthesis was performed for the main-shock using elemental earthquakes of about M6, and it was shown that the difference in rupture propagation characteristics between the main-shock and elemental earthquakes greatly affects the reproducibility. In addition, in the seismic motion prediction, it was shown that the prediction accuracy may be improved by using an earthquake that is close to the theoretical rupture propagation characteristics of the assumed earthquake as an elemental earthquake. Finally, we proposed a method to correct the rupture propagation effect of elemental earthquakes and demonstrated its effectiveness and future issues by verifying it at multiple observation points.

We investigated the characteristics of seismic ground motions that cause serious damage to wooden houses with high strength, and the conditions under which they occur. We found that such seismic ground motions had large 0.5–1 second responses, and when the 0.5–1 second acceleration response exceeds 1800 cm/s² with a damping constant of 5%, they brought about severe damage to wooden houses with high strength. However, such seismic motions rarely occurred in the past. Therefore, we investigated the conditions under which such seismic motions occurred using KiK-net station records. We found that such seismic motions occurred in the condition that the average shear wave velocity in the surface layer of 30 m is about 200 to 400 m/s, which accounts for half of the whole, and the peak ground acceleration at the engineering bedrock is more than 300 cm/s². Therefore, such seismic motions will likely occur in the future.

Recently, an M7-class earthquake within the Philippine Sea plate has been highlighted as the most disastrous earthquake for the Tokyo metropolitan area. We performed broad-band strong motion simulation of such an earthquake by the empirical Green's function (EGF) method using the strong motion records obtained by MeSO-net, which has been deployed in Kanto region at minimum interval of 2 km. Our fault models corresponded to the two nodal planes of the EGF event with one strong motion generation area whose parameters followed the fault model used in the strong motion evaluation by Cabinet Office (2013). The strong motion generation area was divided into subfaults having the EGF event size estimated by the waveform modeling of the EGF event. The rupture propagation directions were assumed toward the Tokyo metropolitan area. MeSO-net stations have accelerometer at 20 m depth, therefore, the seismic intensities on the surface were estimated using the temporal observation data on the surface. A comparison of the acceleration response spectra between the two fault models shows that the response around 1 s amplified for the stations located in the rupture propagation direction. The seismic intensity distribution shows that there are more stations recording large seismic intensities in the rupture propagation directions than around the source areas. For such stations, particularly located around the western Tokyo prefecture, larger seismic intensity was also observed for the EGF event. The distinctive seismic intensity distribution derived in this study was reproduced by the strong motion characteristics included in the EGF event and rupture directivity effect.

Fault displacement is an important hazard to be considered in the seismic design of structures, along with strong ground motion. In recent years, standards and safety guides for probabilistic fault displacement hazard analysis have been published, and social demand for probabilistic verification of fault displacement underneath critical facilities has increased. However, the practice of this method is very limited worldwide, and there are no reports of its full-scale implementation for a specific structure in Japan. In order to achieve wide application in the future, we should first practice probabilistic fault displacement hazard analysis based on a model with higher accuracy, and then understand the current issues properly. Here, we practice the probabilistic fault displacement hazard analysis using model of seismic source characteristics at the Ikata site based on guidelines for SSHAC Level 3, and report on the specific issues in its application at the practical level, referred to the knowledge obtained from the observation data of the 2016 Kumamoto earthquake.