In the urban center, mid-to-high-rise buildings stand side by side and form city blocks. To date, most of these buildings have been of earthquake-resistant structures. However, due to the recent spread of structures with damping systems, there are cases where a building with high structural damping is built adjacent to buildings with a similar size and low structural damping. Based on this, in the study, we modeled two buildings with the same shape and their surrounding ground and performed frequency response analyses using parameters such as the damping ratio of one building, the distance between the buildings, the soil condition between the buildings, and the properties of the surface layer. The amplitude transfer functions and responses of the buildings to a seismic ground motion were obtained, and considerations on the dynamic soil-structure interaction between adjacent buildings with the same size but different structural damping were made. As a result, it was confirmed that a building with high structural damping on a soft low-damping surface layer may affect an adjacent building with low structural damping.

We compared the near-fault records of the 2023 Turkey earthquakes with past crustal earthquakes. The PGA, PGV and the short-period amplitudes in the pseudo-velocity response spectra near the fault did not differ significantly from those of earthquake records during lower Mw earthquakes, but the amplitudes of long-period in response spectrum tended to be larger as Mw is larger. The trend of saturation of near-fault ground motion amplitudes suggests that only SMGAs close to the station may contribute to the amplitudes. With five fault models with different lengths, we estimated near-fault ground motions using a hybrid method of the statistical Green's function method and the wavenumber integration method. For faults longer than 50 km, the near-fault PGA and PGV were small. The maximum amplitude near the fault was most influenced by the nearest SMGA station, and it is speculated that SMGAs that are a certain distance away do not contribute to the maximum amplitude due to the fault rupture directivity effect.

This paper examined the characteristics of in-service reinforcement as sustainability for infrastructure structures. The aging process on RC piers is defined as the process of corrosion of steel bars due to degradation factors such as carbon dioxide, water, chlorine, temperature, etc. This process is evaluated by simplifying the effect of concrete carbonation by the steel corrosion rate. The study investigated the reinforced effect of the earthquake engineering when reinforcement according to the Upgrade Reinforcement Manual is applied in the service period. The effect was characterized by the yield seismic intensity, plasticity factor, damage index, and required yield strength spectrum. By displaying the seismic spectrum on the required yield strength, the reinforcement history of aging and durability performance could be determined.

We attempted to decompose the fault-displacement distribution by using bell-shaped functions, assuming that the fault-displacement distribution consists of the superposition of the contribution from each strong motion generation area (SMGA). We obtained the shapes of fault-displacement distribution for several source models with SMGAs by dynamic rupture simulations and clarified the relationships between the number and the depth of SMGAs and the shapes of fault-displacement distribution by decomposing them with the bell-shaped functions. We furthermore found that the fault-displacement distribution of the 2016 Kumamoto earthquake could be decomposed into single (Hinagu fault) or multi (Futagawa fault) bell-shaped distribution(s), which demonstrates the correspondence to at least the number of SMGAs. Our results suggest the possibility of evaluating the appropriate positions of SMGAs by decomposing fault-displacement distribution.

The model condition for spontaneous initial rupture were discussed by dynamic fault rupture simulation. The dynamic fault rupture simulation was conducted using the three-dimensional finite difference method without giving a priori rupture starting area by changing the coefficient of friction or changing the frictional constitutive law. It was conducted on condition that the shear rigidity was changed along the fault plane and that the shear stress on the fault plane was loaded by forced displacement of model edges. Conditions of the shear rigidity along the fault plane was investigated that tended to cause spontaneous initial rupture. As a result, it was found that spontaneous initial rupture tended to start from the low velocity side of the boundary where the shear rigidity was changed.

Large and long-period velocity pulses observed in the parallel direction at near-fault stations are important in engineering. A previous study has indicated that the existence of the ground surface and sedimentary layers affects fault rupture. In this study, dynamic rupture simulations using the finite element method are conducted and the interaction between fault rupture and sedimentary layers is discussed. The influence of the sedimentary layer was examined from the shape of the near-surface slip rates. τ_h (pulse width) is longer and τ_r (rise time) is shorter when the sedimentary layer exists than in the case of no sedimentary layer.

In order to generate useful information on the amount of house cleanup work and shortages after a disaster, we used work management data of disaster volunteers at the Disaster Volunteer Center in Mashiki Town, Kumamoto Prefecture, in 2016 to understand the actual work situation in the affected area. Existing building damage survey data was used to determine the amount of house cleaning work per week and to identify the work characteristics of each district. The 250 m mesh visualization was conducted. As a result, it was estimated that the proportion of self-help work tends to be higher in areas where agriculture and forestry are practiced, while requests for mutual aid tend to be higher in urban areas. In addition, work tended to be more prolonged in areas that were half or partially damaged than in areas that were severely damaged. Disaster volunteerism was found to be about 1-5% of the total, including self-help efforts. A coefficient for calculating the amount of work per 1,000 damaged houses in the model area was derived.

We estimated the site amplification characteristics at 16 temporary seismic stations deployed in Iwaki City, Fukushima Prefecture, from December 2014 to September 2015. The generalized spectral inversion technique was applied to records of interplate and intraplate earthquakes that occurred between January 2012 and December 2021. The analysis utilized strong-motion data from 18 seismic stations operated by the National Research Institute for Earth Science and Disaster Resilience (NIED) and seismic intensity stations of the Japan Meteorological Agency (JMA), located in and around Iwaki City. From these data, we separately estimated the source and propagation path effects for each earthquake. The site amplification at the temporary stations was then derived by removing these effects from the observed spectra. In the central area of the Taira District, significant amplification was observed in the 0.7-2 Hz frequency range, possibly due to the presence of a widespread alluvial plain. Ground motions in this area were larger than those recorded at nearby permanent strong-motion stations.

Horizontal vibration of a building can be considered from the perspective of wave propagation between the foundation and the rooftop in the vertical direction. Using wave interferometry, it is possible to extract the intrinsic damping of the building through the transfer function of the up-going and down-going waves of the new wave field (impulse response) when the virtual source (impulse) is placed on the roof. Previous studies have examined the effectiveness of the method using homogeneous and heterogeneous 1D stratified models and the effects of effective frequency range and other factors using Ricker wavelets. In this study, shake-table tests on a building model are conducted to investigate the practicality of the method to evaluate the damping factors of each mode from the damping functions.

Axial load acts on a pile head due to overturning moment during an earthquake. However, knowledge on the settlement of pile foundations under cyclic loadings has been limited. This study investigated the settlement of a pile under cyclic axial load based on monotonic and cyclic vertical loading tests on a pile in a sand deposit. The following results were obtained: 1) The settlement of pile subjected to the cyclic loadings were larger than that subjected the monotonic loading at the same load amplitudes. 2) The settlement of the pile under cyclic loadings increased logarithmically with the number of loading cycles. 3) The settlement of pile subjected to the cyclic loadings can be obtained by the proposed method.