The 2016 Kumamoto earthquake caused damage to the Soryo Bridge, where the middle pier settled approximately 30 cm with respect to the left bank abutment. The authors have previously analyzed this damage by considering only liquefaction of sandy soil. In this study, the authors reexamined the damage caused by the settlement of the middle pier using a two-dimensional effective stress analysis, taking into account softening due to the repetitive action of volcanic cohesive soil derived from Mt. Aso. As a result, it was confirmed that the degree of settlement of the middle pier increased when the repetitive softening of clay was taken into account, and that the possibility of re-liquefaction of sandy soil due to earthquake motion occurring at short time intervals was high.

Topographic site effects were examined based on the spectral ratios of seismic records on a crest of a simple-shaped ridge and a lower station with flatness topography (reference point). The topographic effects more clearly appeared in the orthogonal direction to the ridge axis than in the ridge axis direction, and the spectral characteristics showed from around 2 Hz to a nearly flat peak up to 5 Hz to the reference point. The topographic effect was greater at the edge of the ridge elongation than at the center of the ridge, even on the same ridge crest. Based on the numerical simulations using DEM, the three-dimensional topographic model better reproduced the difference in the topographic effect between the center and the edge of the ridge compared to the two-dimensional model, indicating the importance of considering three-dimensional topography. The correlation between the obtained topographic site effects and topographic indices was examined to identify a proxy for assessing topographic site effects. The results showed that the ridge-valley degree, defined from positive and negative openness, has a higher correlation than the general topographic index, the shape ratio (width-to-height ratio of the ridge) and is effective in evaluating the topographic site effects. Furthermore, the ridge-valley degrees at K-NET and KiK-net stations were investigated, and the effectiveness of the ridge-valley degree in evaluating topographic site effects was confirmed by comparing AKTH04, which has a significant ridge-valley degree, with the nearby station with a less ridge-valley degree through the site condition proxy, the ridge-valley degree, and peak accelerations during the 2008 Iwate-Miyagi Nairiku earthquake.

The preparation of a mesh is a costly procedure in finite element analyses. Energy-based overset finite element method (EbO-FEM) is a method that facilitates the creation of the mesh by composing several subdomains into a single computational domain. This paper presents a fundamental study to extend the EbO-FEM to dynamic problems, focusing on the one-dimensional scalar wave problem. In particular, the relationship between the parameter representing the degree of coupling and the magnitude of the undesired reflected waves generated at the overlapping regions is investigated. The results show that the EbO-FEM provides as accurate a solution as the conventional FEM when adopting well-tuned values as the parameter. Error analysis in the frequency domain showed that the unwanted reflected wave generated at the overlapping region is controlled by the characteristic of the incident wave and the size of the overlapping region. Numerical examples of coupling the computational domain with different materials implied that the overlapping region acts stiffer than it is. These results suggested that the overlapping region should be as small as possible to obtain an accurate solution, even though the EbO-FEM is an overlapping mesh method.

In order to improve the accuracy of strong ground motion prediction, a propagation path attenuation model that depends on the apparent incident angle, which is derived from observational records, was introduced, and the effects on the calculated waves were investigated. The statistical Green's function method was used as the calculation method, and the results were compared with the conventional attenuation model. Assuming an M7-class fault as the source, we set up a strike-slip fault and a reverse fault model to calculate the seismic ground motion. In the case of the apparent incident angle dependent model, the effect of increasing the amplitude was observed directly above the fault distribution range, especially near the top of the asperity, and that the effect was small in other regions. In addition, the so-called hanging wall effect, in which the amplitude on the hanging wall side was increased in the reverse fault model, was observed, and the effect of the apparent incidence angle-dependent attenuation was suggested to further increase the amplitude in this area. These results suggest that the apparent incidence angle-dependent attenuation could be one factor to explain the large amplitude ground motion observed near seismic fault.

As described above, in the case of large earthquakes, it has been confirmed that the area where the increase in amplitude is significant due to the apparent incidence angle-dependent model does not extend over the entire area directly above the source fault, but may be limited to a narrower area depending on the position relative to the fault or asperity. It has also been suggested that in the case of reverse faults, the hanging wall effect and the amplitude increase effect due to the apparent incidence angle may overlap.

In order to clarify the uncertainty in the evaluation of the seismic stability of slopes by the modified Fellenius method, the results obtained from the existing centrifugal experiments were organized and analyzed. As existing experiments, 15 cases were used among a series of centrifugal loading experiments on the seabed slope model, and the experimental conditions, the strength characteristics of the seabed slope model ground, and the experimental results were arranged and analyzed. For analysis of uncertainties, the acting seismic coefficient at the time a slip surface was formed in the slope, the yield seismic coefficient obtained by the modified Fellenius method for an arc-shaped slip surface set near the slip surface, the slip safety factor at that time are evaluated. In addition, as for the uncertainty of the method used for seismic stability evaluation of slope, the acting seismic coefficient at the time a slip surface is formed has a large variation but is small. It was found that the slip safety factor at that time was larger than the value of 1.0 when calculating the yield seismic coefficient, although there was some variation.

A study focusing on the nonlinear behavior of the ground and structure was conducted to improve the combination of ground deformation and inertial force when using the seismic deformation method. Specifically, dynamic analyses were conducted for various types of grounds and structures under the condition that one of them became nonlinear, and the combinations of actions were sorted out. As a result, it is clarified that the combinations of actions can be improved by considering not only the relationship between the natural period of grounds and structures, but also the degree of nonlinearity of each. This makes it possible to easily consider the degree of nonlinearity, and to improve the combination of ground deformation and inertial force.

We studied countermeasure technology based on the concept of seismic-tsunami isolation in order to contribute to disaster prevention of onshore structures. And, we conducted tsunami model experiment to examine the reduction effect of wave pressure by cushioning materials. As a result, it was confirmed that the wave pressure acting on the structure could be reduced by installing easily deformable cushioning material between the structure and the tsunami. In addition, as a result of the 3-D FEM analysis, it was confirmed that the stress generated in the structure changes greatly depending on the magnitude and the vertical distribution shape of the wave pressure.

This paper proposes a modal analysis method based on the energy-based overset finite element method (EbO-FEM) for rigid frame bridges. Rigid frame bridges and the foundations have complex geometries, which makes the mesh generation for finite element analysis expensive. The EbO-FEM has been developed to reduce the cost of mesh generation by allowing the use of nonconforming meshes without iterative computations. However, the EbO-FEM has only been applied to the static analysis and the applicability for the modal analysis has not been investigated. We applied the EbO-FEM for the finite element modal analysis, evaluated the accuracy of the method by comparing the solutions with existing FEM solutions, and utilized the EbO-FEM for the parameter identification with records of microtremors through the following procedure. First, a modal analysis of the virtual cantilever beam was performed to verify the accuracy, and the EbO-FEM solution agreed well with the conventional FEM solutions under different discretization scales, where overlapping regions is carefully localized. Second, the natural vibration modes and frequencies are estimated using the EbO-FEM for a frame bridge under construction. The EbO-FEM gives similar natural vibration modes to ones estimated by the frequency domain decomposition (FDD) method, and the elastic moduli of the surface soils were estimated so that the corresponding natural frequencies were consistent. The estimated elastic moduli were not significantly different from the data obtained from the preliminary survey. Above all, it was found that EbO-FEM can be as accurate as conventional FEM when the mesh overlapping is carefully minimized, in the modal analysis in spite of allowing non-conforming mesh.

Rapid damage assessment by a structural health monitoring system is expected to prevent casualties caused by the collapse of wooden buildings due to repeated seismic motions. While neural networks are known to be a powerful tool for determining the risk of collapse based on the response records, they are not good at classifying untrained damage patterns. This study proposed a method to consider the diversity of damage patterns in the construction of a damage classifier for wooden buildings. This is achieved by using pulse-like simulated ground motions as the input ground motions for seismic response simulation of a target building model in the development of the training dataset. The effectiveness of the proposed method was validated by comparing its accuracy on test data.

In current seismic design, response history analysis is not required for high-rise buildings shorter than or equal to 60 m which are designed using the lateral load-carrying capacity calculation or the limit strength calculation. The lateral load-carrying capacity calculation is more commonly used among these two design methods but cannot evaluate the displacement demand of buildings explicitly. It is not generally considered whether the story drift for buildings designed based on this calculation method will exceed the safety limit deformation defined by the limit strength calculation. The objective of this study is to clarify seismic displacement demand of a high-rise RC building designed based on the lateral load-carrying capacity calculation. A comparison was made between the story drift evaluated by both response history analysis and equivalent linearization method of the limit strength calculation method and the safety limit deformation.

A multi-spring (MS) model is generally used for reinforced concrete members, especially columns, for nonlinear analysis of high-rise buildings. The MS model is suitable for considering the interaction of axial load and bending moment. However, few previous studies have discussed the accuracy of the axial deformation behavior of the MS model. The accuracy of axial deformation is important to discuss the seismic response behavior of tall buildings, which shows overall flexial deformation during earthquake. The static loading tests subjected to varying axial load and lateral load were conducted to examine the experimental reproducibility of MS model. When the confined effect of concrete is taken into account, the experimental reproducibility of horizontal behavior in experiments under variable axial load is improved. However, slight effect observed in the axial behavior. Then nonlinear characteristics for the axial spring of MS model has been taken into account to improve model accuracies.

We investigate the surrogate model by machine learning for rapid estimation of response spectral distribution in earthquake disaster, which can take into account nonlinear site response and period-dependent spatial correlation of response spectra. We proposed a method to simulate the above behavior by combining interim outputs by spatial interpolation with linear soil amplification and deep learning networks. The results for the city of Sendai showed that the learned model is effective in estimating the response spectrum distribution considering the effect of nonlinear amplification for periods of about 1 second or less, and can be used as a surrogate model for the existing methods with an accuracy of about 0.1 in the normal log standard deviation. On the other hand, the accuracy of the intermediate output was higher for periods longer than about 1 second. The reason for the lower accuracy at longer periods may be the effect of surface waves or the period dependence of hyperparameters not considered in this study, and improving the accuracy at longer periods is an issue for future work.

For decision on safe evacuation and continued use of buildings, structural health monitoring systems with several sensors have been developed for mid- and hi-rise buildings. In this paper, a simple monitoring method for low-rise buildings is introduced using only one sensor at the top of the building. In the method, predominant frequency of building and its shift during an earthquake is extracted using nonstationary amplitude spectrum applying multi filter technique to analysis of severe earthquakes. Based on the seismic observation records of a heavily damaged low-rise RC building during the 1994 Sanriku Haruka-oki Earthquake, the effectiveness of this method was demonstrated by comparing with the natural frequency evaluated by the ARX model from the records of two or more sensors. In addition, based on an analysis of observed records of a mid-rise SRC building damaged in a major earthquake, the characteristics of the proposed method were examined by comparing it with the characteristics of a low-rise building.

The experiments of post-installed adhesive anchoring systems of epoxy injection resin type were taken in focusing on bond failure (bond strength) during fire assumed joints between members in long term. Concrete strength such as high strength (σ_B= 44.8 MPa) and low strength (σ_B= 17.5 MPa) were used as one of parameters. The following conclusions were recognized by their experiments.

1. Bond strength decrease in accordance with increase of temperature in post-installed adhesive anchors.

2. The temperature in bond failure on low concrete strength were lower than ordinary concrete in the past.

3. The influence of concrete strength on high concrete strength for bond strength were not recognized that is, the temperature in bond failure on high concrete strength were not usually lower compared to the past results as the sane conditions.

4. The border move on between bond and the surface of rebars from between bond and the surface of concrete during fire as the difference of ordinary conditions.

5. The influence of the different shape in the surface of rebars were recognized on bond strength during fire.

Although most natural disasters such as major earthquakes are spatially localized, the strong interdependencies among economic entities can make their impacts ripple through the nation for several years, producing substantial economic losses. Enhancing disaster resilience necessitates a comprehensive assessment of the long-term economic impacts of candidate recovery plans considering the complex interrelationships of economic entities, and other real-world constraints such as lifeline access, transportation, and government policies. This requires fine-grained modeling of the economy and infrastructure as an integrated system. To attain this objective, we developed a high-performance computing (HPC) extension for an agent-based economic model, making it possible to efficiently simulate large-scale economies consisting of hundreds of millions of agents at a 1:1 scale. This paper presents the validation of the developed system for the Japanese economy by reproducing the past observations at the national and sectoral levels. As a demonstrative application, we present a simulation of a post-disaster economy considering hypothetical disaster scenarios.

Cross-laminated timber (CLT) mid-to-high-scale buildings are gaining widespread attention recently. However, developing damage control technology for CLT buildings to minimize damage and enable continued use after large earthquakes has not been established. This research aims to realize a wooden building with excellent performance maintenance after an earthquake experience by introducing a passively controlled CLT structure that uses a rocking wall column and a damper as part of the CLT earthquake-resistant frame. In previous research, the full-scale static shear test was conducted on a 1-story 1-bay passively controlled CLT structure by MATSUDA et al. (2023), and the passively controlled CLT structure, which has high performance of energy absorption and high origin return characteristics, were developed. To actively rock the wall columns, the column-beam joints of the passively controlled CLT structure are designed to have low rotational stiffness. In that test, while the behavior of the frame was analyzed, the behavior of the column-beam joint was not comprehensively identified. Therefore, we conducted the full-scale test on the column-beam joint of the passively controlled CLT structure to understand the mechanical behavior of the column-beam joint. Furthermore, the mechanical behavior of the CLT rocking frame proposed in this study was understood. We confirmed the differences in stiffness, maximum moment, force applied to the embedded surface, and size of the embedment and uplift when the joint shape assumed various shapes and positions. We also proposed a method to evaluate the relationship between the bending moment and rotation angle on the column-beam joints. Applying the idea of embedded triangular to the deformation of column-beam joints is a simple evaluation method that uses the compressive force of embedded triangular and the compatibility for the embedded triangular Equations. In this case, it was necessary to evaluate the uplift of the column-beam joints in advance, and we created a spring model to evaluate the uplift. Spring model was characterized by the stiffness of the tensional bolt, washer, and CLT connected in series. Although additional studies are required to reproduce the yield strength, it is believed that the test results can be accurately replicated.

Theories of behavior change for health have been synthesized and successfully applied to real problems such as smoking. Health and disaster risk reduction have a similarity in that behavior changes of selves and groups lead to risk reduction. Therefore, considering the disaster countermeasures in the framework of the theories developed in health problems and adapting practical health promotion approaches to disaster problems are beneficial in clarifying the weak points and deriving new approaches in the disaster countermeasures. In this study, we attempted to associate existing earthquake countermeasures with the framework of Prochaska’s stage of change model (pre-contemplation, contemplation, preparation, action, and maintenance). We found that individual supports to those in the action and maintenance stages are weak in the earthquake countermeasures landscape compared to that of health promotion. In addition, for the problem of raising the responsive ability against earthquake warning/advisory information, the necessity for such individual supports and the human resources providing them were highlighted. It is considered effective, in the future, to evaluate the effectiveness of the stages of change model to disaster countermeasures and to associate disaster countermeasure items in finer scales in the model (such as personal (biological, psychological), inter-personal (social, cultural), organization, community, environment, policy).

Blind faults, which cannot be identified in advance, in/on the Philippine Sea plate and the Pacific Sea plate affect greatly for seismic hazard in the Tokyo metropolitan area (NIED, 2023). Basic idea of performance-based design (JSCA, 2018) is that seismic damages are controlled by strong ground motions corresponding to some representative recurrence periods. So, the relation between intensity of ground motions and recurrence periods must be precisely known. In this study, we evaluated velocity response spectrum at Shinjuku corresponding its recurrence periods of 500, 1000, 2500 years by blind faults in/on the Philippine Sea plate and the Pacific Sea plate near the Kanto area. The velocity response spectrum for recurrence period of 1000 years was 80 – 110 cm/s and predominated at periods of 2 s and 7.5 s. These predominancies were due to S-wave amplification of the layers above the layer with S-wave velocity of 1.5 km/s and the seismic bedrock respectively. Peak amplitudes at 2s and 7s were about 10% and 4% bigger than average amplitudes of the nearby periods.

In this study, five types of optical fiber cables were buried in the test site for DAS measurements. Three types of interrogators were independently tested using the buried cables, and multiple geophones were deployed with equal spacing for comparison with DAS records. Comparison with the strain rate records calculated by dividing the difference between adjacent geophones by the installation interval confirmed that the excitation records by the hummer were successfully obtained, and that the microtremor observation records could be used to estimate the phase velocity in the frequency band of approximately 2 Hz or higher. Seismic interferometry analysis of the DAS records and the combination of DAS and microtremor records showed that the dispersion curves were consistent with the Rayleigh wave phase velocity estimated by the microtremor survey.

This study conducted centrifuge model experiments on two different soil models with varying spatial arrangements of low relative density regions within dense soil. The effects on soil response and seawall pile foundation response were examined. The results showed minimal differences in excess pore water pressure response in the soil and bending strain response in the piles between the two cases. Thus, the spatial arrangement of low relative density regions had little impact.

In recent years, small buildings are often built on developed ground, and the proportion of ground reinforcement has increased. In conventional ground reinforcement design for small buildings, seismic force design has been omitted without a clear evidence. In this study, 1) the damage of the ground reinforcement under great earthquakes by the questionnaire survey and 2) verification of the horizontal resistance safety by the parametric study were performed. It was found that there was no damage due to the level 1 earthquake motion, and safety against seismic force is ensured sufficiently if the contact pressure of ground is as small as a detached house.

Microtremor measurements were conducted at a reclaimed site on the Tama Hills to investigate the distribution of ground-motion characteristics in this area. The area is divided into three levels, with elevations ranging from 110 to 150 meters. The upper level consists of naturally deposited loam layers, while the middle and lower levels are composed of subsurface soils and fills. It was found that the peak period of the H/V spectral ratio of microtremors (Tp) increases with the thickness of the subsurface soils at the borehole points. The result enabled us to conduct high-density microtremor measurements on a cliff edge and in a plaza of the middle level, then depict the spatial distribution of Tp. Measurements at the cliff edge indicated that ground motion was likely amplified in the direction perpendicular to the edge. The results showed that spatial changes in Tp correspond well with the old topography. Additionally, it was found that the H/V spectral ratio of fill areas where landslides occurred in the past exhibits marked peaks, and Tp evaluated at the station where seismic amplification was observed corresponds to the peak period of strong motion spectra.

In this study, we conducted microtremor and gravity observations in the Otsuka area, Tottori City, to investigate the subsurface structure and characteristics of strong ground motion characteristics of microtremors in the vicinity of the Yoshioka fault of the Tottori Earthquake in 1943. The shape of H/V differed in the direction of horizontal motion near the fault line, and the subsurface structure model also differed between the areas near the fault line and other areas. The three-dimensional density structure obtained from the gravity anomaly shows a sharp drop in the south-falling bedrock in the vicinity of the fault line.

We propose a systematic fault displacement evaluation method using remote sensing techniques and discuss its present issues and prospects. By calculating relative displacements on measurement lines across a fault trace with a certain interval to the high-resolution 3-D surface movement data acquired using differential InSAR and LiDAR, the method supplies us with displacements, slip senses, and dip angles of the fault. Applying it to many secondary faults widely observed during the 2016 Kumamoto Earthquake, we elucidate that the displacements decrease according to the distance from the primary fault.

The amount of survey work required for post-earthquake residential damage assessment is enormous, and the degree of damage is assessed by administrative staff based on visual inspection of the house's exterior. Therefore, this study aims to automate the residential damage assessment survey using AI to improve efficiency. For this purpose, this paper attempts to construct a system to calculate the repair estimates for damage rate calculation. Specifically, we developed a program that calculates repair estimates based on the classification of building exteriors based on area suggestions. Experiments were conducted on the developed calculation program, and we examined the predictability of the results of the judgment of the repair cut-off.