Residential ground located at the inclined area had severe damage during the 2016 Kumamoto earthquake. This paper reports test results obtained from the undrained cyclic shear test using volcanic clayey soils sampled from Mashiki Town damaged sites for clarifying the deformation mechanism of the residential ground. In the tests, specimens were consolidated by confining pressure at the sampling depth, after applying the initial shear stress corresponding to inclination, the random seismic shear stress, which was estimated from actual seismic records obtained at the Mashiki Town, was applied to the specimen. As a result, it was shown that even unsaturated volcanic clayey soil, excess pore water pressure ratio was generated up to 0.9 and deformed over 15% shear strain. Furthermore, a large shear strain was developed to the inclined direction in case of initial shear stress applied test. Therefore, it is considered that, during the 2016 Kumamoto earthquake, residential ground damage was caused by large shear deformation of volcanic clayey soil subjected to large shear stress.

According to previous studies, in the sedimentary plain on the irregular bedrock such as the Kanto basin, Japan, the amplitude, duration, and predominant period of observed long-period ground motions vary with the hypocenter location due to the difference of the propagation path. In this paper, we investigated the propagation path effects (the relationship between amplitude and phase characteristics and epicenter distance) and the propagation path of surface wave recorded in and around the Kanto Basin. As a result, there were variations in path effects depending on the source location, period, and component. One of the causes of this variations was that the location where surface waves are concentrated differs depending on the source location. Furthermore, surface waves were likely to be concentrated the locations where the basin edge surrounds the inside of the plain and near the basin edge reflecting and refracting surface waves.

A phase transform angle is known to be an important parameter in the liquefaction analysis, but researches on the phase transform angle was few; it is assumed to be constant or to be proportional to the internal friction angle in the practical use. In this study, we read off phase transform angles and internal friction angles from the cyclic shear test results on sand under the triaxial condition. It is found that phase transform angles scatter between18 and 28 degrees, and the phase transform angle is strong correlation with the internal friction angle when fines content is less than 20 %. Based on findings, empirical equation is proposed in which phase transform angle is expressed as a function with respect to the internal friction angle.

Source, propagation path, and site characteristics were separated from strong motion records during the 2016 Kumamoto earthquake sequence using the spectral inversion technique. We evaluated site amplifications from the seismic bedrock to the ground surface for 177 strong motion stations in and around the Kumamoto prefecture. Site amplifications at stations located inside plains and basins were larger around 1 Hz than those at stations outside plains and basins. From the separated source spectra of 182 events (M_JMA: 3.0-5.5), we calculated stress drops of 91 events which have moment tensor solutions by F-net, and found the depth dependence of them. The estimated 1/Q_S value was modeled as Q_s=73.5f^0.83, which is comparable to those of previous studies in and around the Kumamoto prefecture.

On April 16, 2016, an earthquake of Mw 7.0 occurred in the Kumamoto prefecture, in the central part of Kyushu island, Japan. At Kurokawa area in Minami Aso village, the target in this study, was seriously damaged, such as collapses of buildings including student dormitories. In this study, we estimated detailed building damages distribution in the target area from field and aerial photograph. We also estimated spatial distribution of H/V peak period and S-wave velocity structures from microtremor observations to evaluate characteristics of local amplification in the area. As a result, the building damages were not well explained simply by the local amplification characteristics.

The installation of gravel drains is one of the liquefaction countermeasures that has been used extensively. However, there are not many experimental studies that verified its effectiveness in a realistic stress level, and uncertainties still remains that has not been studied sufficiently. In a present study, a series of centrifuge tests were conducted focusing on the influence of permeability of drains and liquefaction layer and the effective confining pressure on the dissipation effects of excess pore water pressure by gravel drains. The experimental results showed that the higher the permeability of the liquefaction layer, the higher the dissipation effect by gravel drains. In addition, gravel drains effectively prevented liquefaction at a greater depth as compared with at shallower depth. On the other hand, the duration of liquefaction was significantly shortened even when the permeability was low and drains could not suppress the occurrence of liquefaction.

The surface faults appeared and the permanent displacements were observed during the mainshock of the 2016 Kumamoto earthquake. In order to reproduce or predict the permanent displacements very close to the fault trace, it is necessary to consider the shallower rupture area than the seismogenic layer which is not taken into account in the strong motion prediction procedure, called Recipe, by the Headquarters for Earthquake Research Promotion, Japan. In this paper, we aimed to construct the fault rupture models for the 2016 Kumamoto earthquake to reproduce the observed strong motions and the permanent displacements in the region very close to the fault trace while taking advantage of the Recipe. As a result, it was shown that the strong-motion pulses and the permanent displacements of the observation records at Nishihara station, 700 m from the fault trace, and Mashiki station (KMMH16 by KiK-net), 2 km from the fault trace, can be reproduced well by adding a shallow fault model having a large slip region to the deep fault model made by the existing procedure of evaluating the parameters for predicting strong motions.

The strong motion generation areas of major historical earthquakes of the Tokyo metropolitan area such as the 1703 Genroku, the 1855 Ansei-Edo and the 1923 Great Kanto earthquakes are obtained using seismic intensity inversion analysis based on the attenuation relationship and site factors derived from recent measured intensity data. The short-period spectral level of acceleration source spectra is estimated from the empirical relational expression with normalized seismic intensity level based on the seismic intensity inversion results. Although the 1703 Genroku and the 1923 Great Kanto earthquakes along the Sagami Trough are similar in magnitude and short-period spectral level, the strong motion generation areas related to seismic intensity are found to be different. The 1855 Ansei-Edo earthquake is estimated to occur about 40 km deep in northern Tokyo Bay and to be a little bit smaller than the other two earthquakes.

An on-site earthquake warning for the threshold of earthquake motion is generally applied to an amplitude of S-wave, which is dominated in seismic waves. To issue the earthquake warning for the threshold of earthquake motion earlier, in this study, we investigated the applicability of earthquake warning for the threshold of P-wave in seismic data, using an amplitude ratio of S-wave to P-wave. At first, we theoretically led that the amplitude ratio of S-wave to P-wave were affected by both subsurface P-wave and S-wave velocity structures at the site. Also, we could stably extract the amplitude ratio of S-wave to P-wave, using seismic data recorded. As the results, S-waves predicted by P-waves using the amplitude ratio of S-wave to P-wave at seismic stations were in good agreements with observations. Finally, we concluded that this method can potentially issue the earthquake warning earlier than the previous method by the time of Ts-p.

When using a potentially liquefaction foundation, the evaluation of settlement is necessary because the bearing capacity of the ground is lost. In this report, we tried to evaluate the actual settlement due to liquefaction by effective stress analysis for spread foundation buildings in Rokko Island at the 1995 Southern Hyogo Prefecture Earthquake. As a result, if we could properly evaluate earthquake response on liquefied ground, it found that the settlement of spread foundation is predicted by numerical simulation.

Telecommunication conduits are facilities that houses and protects underground cables. Because those were mostly built from 1960s to 1980s, aging is progressing. In addition, conduit at this period is not sufficient in earthquake-resistance, and numerous damages have been confirmed in the past large earthquakes. As a method for repairing existing pipelines, lining technologies forming a coating film with a resin on inner surface of pipes are widely used. Since lining pipe itself has enough strength against earth pressure, effect expecting earthquake-resistances has been studied. The evaluation of seismic resistance of conduits with lining through analysis and experiments are described.

We have analyzed response and damage of buildings due to pulse-like ground motions predicted near faults, assuming Uemachi fault. In this study, we especially aim to clarify effects of pulse-like ground motions including fling step attracted in the 2016 Kumamoto earthquake on building response. Analysis model of buildings apply nonlinear multi-mass-of-freedom-systems, parametric studies are performed by changing height and structural type of buildings. Height of buildings are set from low-rise to high-rise buildings. Structural type are S-structure, RC-structure and base-isolated building. Finally, we try to understand building damage during the past-earthquakes based on the results of earthquake response analysis.

The authors conducted a series of numerical simulations to estimate the tsunami forces acting on bridge girders based on Moving Particle Semi-implicit method. The experimental results provided by the Earthquake Engineering Committee of Japan Society of Civil Engineers, and those performed by Shoji et al. (2016) were employed in this study to evaluate the accuracy of the results of numerical simulations. The wave height, velocity, and forces acting on bridge girders were selected to evaluate the accuracy of the simulations. According to the comparisons between the experimental results and the analytical ones, the initial distance between two particles should be set properly according to the size of bridge girder so as to obtain better results. If the ratio of the distance between two particles to the length of bridge girder is set to be in the range of 1/50-1/40, the analytical result is satisfactory. It was difficult to simulate the vertical force acting on the bridge girder in some cases. To solve this problem, a future study is required.

A dynamic centrifuge model tests were carried out to investigate the seismic behavior of a plate-shape building's pile foundation in the soft clayey ground. Also, the detailed seismic response analysis was carried out to confirm its reproducibility. It was confirmed that it was easy to stabilize the clayey ground made by wet-tamping method and the dynamic response of the building and the pile's stress were well-represented by the analyses, even if the shear strain of the clayey ground was increased by the strong motion.

As for buildings constructed on soil with inclined bedrock, pile foundations with different length or combination of piles and raft are commonly used. In this case, torsional response can be easily excited due to time lag of incident waves from the inclined bedrock. The vibration characteristics of this kind of buildings should be studied sufficiently based on observed records. In this study, we carried out ambient vibration measurements in a seismically-isolated building to extract the structural dynamic properties, along with ground surface and the foundation. In addition, the structural response properties generated by nearby train induced vibration and small earthquakes were studied, and compared with those from ambient vibration.

Sand foundation has been often used as measures against earthquakes for prestressed concrete poles (below, PC poles) on railway viaducts. The sand foundation is a facility expected to reduce vibration of PC poles against earthquake by using sand friction. However, the behavior of the sand foundation PC pole has not been clarified, in the case where these poles had excessive load during a large-scale earthquake. Therefore, we performed static and dynamic experiments of the sand foundation PC poles in order to construct a dynamic analysis model of the sand foundation PC poles against a large-scale earthquake. This paper describes the modeling of sand foundation PC poles in detail.

In case of considering the safety of the structure at the occurrence of a large-scale earthquake, it is important to discuss not only the main shock but also aftershocks and foreshocks. However, these events are not considered in the current design codes. In this study, we proposed the concept of the residual ratio of seismic performance as the evaluation method of seismic performance of a structure affected by multiple earthquakes, and conducted analytical test using past earthquake motion records. As a result, we confirmed that the seismic performance of the structure decreases when the natural period is short and the ductility due to the first earthquake is large.

In the evaluations of seismic risks of existing bridges, the site-specific hazard and the fragility curve with structural parameters uncertainties due to deteriorations should be considered. In this paper, two different locations in Yokohama-city were selected and each site-specific hazard was evaluated. A bridge pier model with seismic rubber bearings was then constructed, and its fragility curve was estimated using the posterior distributions of model parameters in each of the cases; healthy and deteriorated conditions at the bearing. The obtained risk curves showed that the seismic loss rate of the bridge pier with deterioration could be properly evaluated.

A questionnaire survey was conducted for long-term evacuees to Kyoto Prefecture because of the 2011 Great East Japan Earthquake. The survey also conducted for residents who are not evacuees in Kyoto Prefecture. This study is focused to differences of psychological distress between evacuees and non-evacuees, and relationship between psychological distress and personal circumstances which are personal attribute, number of evacuees in household and social relations. In result, ratio of severe depressive tendency of evacuees are 20% higher than non-evacuees, and severe depressive tendency is high in case of evacuees who evacuate alone or with children.

In this paper, the isolation probabilities of hamlets in Yamakoshi village during 2004 Niigata-ken Chuetsu earthquake and in Minami Aso village during 2016 Kumamoto earthquake were calculated and compared with actual isolation damage. Datasets of slope angles, PGAs of earthquake ground motion, and graphs of road networks are necessary for the calculation of the isolation probability. While the isolation probability was high in the whole area in Yamakoshi village, the isolation probability was high in only some hamlets in Minami Aso village. The results show good agreement with the fact that the whole village was isolated in Yamakoshi village and that only some villages were isolated in Minami Aso village.

The Kumamoto earthquakes, which occurred on April 16, 2016 with the moment magnitude of 7.0, caused severe damage to the road network in Kumamoto Prefecture. This study tries to detect the earthquake-induced damage to the roadways using the images captured by a vehicle-mounted camera. To achieve the objective, the authors try to develop an image classifier to detect the earthquake-induced damage to the roadways based on deep learning algorithm. A deep learning module Caffe was employed in this study to develop the image classifier. The authors verified the accuracy of the image classifier comparing with the results of visual damage inspection.

Subsurface structures and characteristics of ground vibration were investigated by analysis of microtremor and seismic data in the central Tottori prefecture, Japan. Subsurface structures were estimated using horizontal-to-vertical spectral ratio (H/V) due to microtremor and seismic data. In addition, we compared a distribution of building damage and characteristics of microtremor H/V. We read the dominant period and classified the categories of shape of H/V to investigate the characteristics of microtremor. As a result, it was found that a difference of the subsurface structure depth to engineering bedrock and a short period component of predominant period less than 1 seconds may have influenced structural damage.

The river-bed ground motion caused by debris flow after an earthquake were simulated using the distinct element method by letting a falling rock collide with the rock surface regarded as river-bed. The characteristics and origin of motion were mentioned by comparing the calculated ground motions with the conditions of changing the rigidity of the river-bed, changing the flow speed, changing flow quantity and considering water. The frequency characteristics of the river-bed motion was affected by the rigidity of the river-bed ground without depending on the height of fall, the number of the falling rocks and the existence of water.

Submarine landslides are well-known inducers of tsunami waves, and multiple studies are available in the literature on hazard assessment for tsunami waves caused by submarine landslides. In these works, changes in the values of physical properties of the ground (such as shear strength) obtained from drilling data were considered as uncertainties associated with the occurrence of submarine landslides to assess the risk of tsunamis; however, statistical variability in these variables was often ignored. In addition, the dispersion of a landslide's position and shape were considered as an arbitrary cross section, but its setting range was limited to the assumed cross section. Herein, a submarine landslide risk assessment method using probabilistic approach was developed to contribute to the development of probabilistic hazard assessment methods for detecting tsunamis triggered by submarine landslides. The proposed method considers the uncertainty of the ground's physical properties, the planar landslide occurrence position, and the moving direction; it was validated by creating a submarine landslide map for model waters.

In the metropolitan area, local governments are trying to increase temporary shelters as a part of earthquake preparedness. However, it is difficult for private sector to provide temporary shelters because of lack of know-how to accept stranded persons as well as liability issues. In order to address these issues, the authors have developed standard manuals to manage temporary shelters and opening kits which visualize manuals based on local action guidelines around Shinjuku Station and verified through field training. These are also verified through a table-top exercise (KUG). In this paper, the authors introduce the method which supports to provide temporary shelter from the examination stage to the implementation stage.