In recent days, inertial sensors based on micro electro mechanical systems (MEMS) technology have been remarkably miniaturized and highly accurate. These sensors have led to the development of compact and inexpensive true-north finders compared to conventional gyroscopes. Accuracy, price, and time required to measure the true north are in a trade-off relationship with each other. We focus on the fact that the direction of seismometer installation does not require such high accuracy and developed a prototype for a rapid measurement system of true north using a 6-component MEMS inertial sensor made of crystal oscillators, specifically for measuring the azimuth angle of seismometer installation. We discuss operations for measurement and algorithms for analyzing the data, and confirmed the prototype worked well.

In order to assist in the performance evaluation of railway structures on earthquake recovery, the authors calculated the restoration period according to the type of structure and damage level, and created a database of the results. In this paper, period required for each work used in the restoration of railway structures was verified based on the restoration period after the 2022 Fukushima Earthquake, in which detailed conditions and processes for restoration have been organized. As a result, we found intermediate damage conditions between large-scale damage and small-scale damage that we did not calculate, so the restoration period in such situation is calculated in the improved database. By using it, it is possible to evaluate earthquake recovery in a more realistic manner.

This report presents that the approximate value obtained by synthesizing Rankine's plasticizing stress by setting the range of passive region where compressive force increases is roughly consistent with yielding ground reaction force obtained in experiment. The results of comparing the results of several experiments when the pipe is pushed horizontally or upward are shown, and it is considered that upper limit of ground reaction force acting on pipe can be evaluated by diameter of pipe, burial depth, unit weight of soil, internal friction angle, and adhesive force. The approximate reaction values can be used for designing calculation of buried pipeline in large deformation.

Recently, PoDIM (POsition-dependent Deep Inpainting Method), which is based on a deep inpainting method, has been proposed to obtain spatially continuous seismic motion data from sparse observations. PoDIM utilizes a positional feature map that represents the degree of amplification or attenuation at each position to realize position dependent interpolation processes. However, since the maps are obtained through the training of a complex deep model starting with random values, it was difficult to interpret their roles. Therefore, in this study, we propose a position-dependent interpolation that can generate and interpret position feature maps based on top surface depth data for multiple s-wave velocities that directly affect the propagation of seismic motions. The effectiveness of the proposed method is then demonstrated through experiments using simulated data of a hypothetical Nankai Trough earthquake.

Two-way travel time information obtained from autocorrelation function analyses of strong motion waveform data can be used to test and improve velocity structure models of sedimentary basins. The waveform data from strong motion stations in the Kyoto and Nara basins were analyzed in this study. The two-way travel time of SH-wave was estimated from the stacked autocorrelation function for each station, and it was compared with the theoretical two-way travel time of deep velocity structure model for the studied areas to check the performance of the present velocity structure model.

By utilizing the six-component information, which includes translational components and rotational components in microtremor observation, various benefits such as the direct calculation of not only Rayleigh wave velocity but also Love wave velocity can be achieved. In this study, two types of microtremor array observations were conducted. Firstly, to assess the performance of the portable rotational velocity sensor, we compared the observed data with those obtained through spatial differentiation of translational data. Subsequently, a method for determining the phase velocity of surface waves using the ratio of translational acceleration to rotational velocity was applied. The validity, prerequisites, and utility of this method were examined through comparisons with conventional SPAC methods and extended SPAC methods.

In structural design, RC shear wall boundary beams are commonly modeled as rigid, including in multi-story seismic wall structures with a soft-first story, and thus the verification (warranty design) of the boundary beams directly above a soft-first story is not commonly performed. However, the boundary beam of the shear wall above the soft-first story may not constrain the shear wall due to the beam deflection. Therefore, the possible failure should be considered in the structural design. This study conducted a finite element analysis on the previous test specimen to investigate the stress levels in the boundary beam of the shear wall above the soft-first story. The analytical results adequately captured the experimental results on load-deformation relationship and failure; therefore, the analytical model used in this research is validated, and additionally, insights were gained into the distribution of axial forces/bending moments acting on the boundary beams, which can be applied to structural design considerations.

Akita city has been frequently damaged by earthquakes that occurred in the inland of Akita prefecture and the eastern margin of the Japan Sea. The author has clarified the damage and distribution of the Rikuu earthquake of 1896, Akita Senboku earthquake of 1914 and Niigata earthquake of 1964, which caused damage in Akita city. In this study, I reconsider the damage of Nihonkai-Chubu earthquake of 1983, which marks the 40th anniversary this year, and clarify the details including the history of the earthquake damage before that. I trace the process of formation of the urban district from old version of topographical map, geological map and city map. It is considered to be important to discuss the damage history by the past earthquakes from the viewpoint of the city formation in considering the future urban disaster prevention.

Underground vertical shafts are affected by the dynamic behavior of the entire surface layer during earthquakes. The simplest and most popular seismic analysis method for them is the seismic deformation method, which uses ground springs as a part of the analysis model, whereas their spring constants are difficult to be estimated. In this paper, the ground spring constants for an example underground vertical shaft are actually calculated by means of 3D-FEM analyses. And the fact is shown that the spring constants vary depending on the displacement patterns of the shaft and the ground due to the three-dimensional interaction of stress and strain in the continuum of the surrounding ground.

This report shows the relationship of improvement range and the horizontal resistance of pile foundations when the static sand compaction pile method is applied as liquefaction mitigation. As a result of case study by stress analysis based on the specifications of the pile foundation building actually built, the safety of the pile can be ensured even if the entire area under the building is set according to placing restrictions or conditions instead of being uniformly improved. It was also confirmed that the placing can be made according to the required performance.

Distribution of ground motion indices is important for characterizing earthquakes as well as early responses to earthquake disasters. We propose a method to estimate the distribution of ground motion indices using the simulation of seismic energy propagation and optimal interpolation of observed ground motions. First, we estimate the distribution and propagation direction of seismic energy by the forward calculation of the combination of optimal interpolation and energy propagation theory. At a certain time, we stop the forward calculation and calculate time-reversal energy propagation. Optimal interpolation is also applied during the time-reversal calculation to compensate for the deviation between calculated and observed seismic energies. We applied the method to the case of the 2016 Kumamoto earthquake. The result successfully retrieved the distribution of strong ground motion indices along the Futagawa and Hinagu fault zones even if some observations near the epicenter were not available.

Centrifugal model tests were conducted to investigate the change in pore water pressure after liquefaction under conditions where impermeable roadbeds of different thicknesses were adjacent to each other like a roadway and sidewalk. If the water film formed at the bottom of the impermeable layer during the dissipation process of excess pore water pressure due to liquefaction is continuous between the roadway and sidewalk areas, the water pressure exceeding the overburden pressure may act on the sidewalk area where the impermeable layer is thinner. This water pressure caused the ground surface of the sidewalk area to rise due to heaving. In the case where a drain was installed in the roadbed of the sidewalk area, little uplift of ground occurred.

In a water supply system, flocs and contaminants in the pipelines are deposited at the bottom of the water supply tank. The authors have confirmed that shaking table tests lift such sediments during sloshing excitation. By the way, large tanks are constructed with several columns inside the tank. In this study, we conducted shaking table tests of a model tank to clarify the influence of sediment uplifting by these columns. The results showed that in the case of the columns, the sediments began to rise from the bottom of the columns immediately after the excitation. The turbidity rose faster, the maximum turbidities were higher, and the high turbidities kept longer than those in the case without the columns.

In the 1995 Southern Hyogo Prefecture Earthquake, many columnar attached structures, including television poles for installing traffic flow monitoring cameras, were damaged such as overturning. However, TV columns are elastically designed for dead load, live load and wind load, and seismic loads are not considered. When the seismic load exceeds the wind load, there is a possibility that the members will be plasticized, so there is a possibility that the structure can be rationalized by considering the plasticization. Therefore, we evaluated the load-bearing performance and damage order of TV columns based on loading tests and reproduction analysis.

In the context of performance-based earthquake engineering, it is crucial to quantify uncertainties in engineering demands, damages, and performance of a building by conducting dynamic analyses with multiple ground motions that reflect the uncertainty of seismic hazards. However, performing a large number of dynamic analyses that include the elastoplastic range requires significant computational costs. To address this issue, response surface methods that approximate dynamic analyses with cost-effective statistical models are expected to be beneficial. This paper proposes a response surface method for multiple ground motions based on multi-task feature learning, demonstrates its efficiency compared to treating ground motions independently, and investigates its applicability to the performance-based seismic design optimization.

In the seismic design of port and harbor facilities in Japan, acceleration time histories considering site amplification factor (hereinafter called SAF) are used as design earthquake ground motions. Evaluation methods of site amplification factors based on in-situ earthquake observations is used in Japanese port area. In the method, SAF of the target site is calculated multiplying a SAF of the reference site (strong-motion station) evaluated by the generalized inversion techniques (hereinafter called GIT) by a geometric mean of a spectral ratio (hereinafter called SR) of the two sites ((1) the target site, (2) the reference site). In the calculation of the GIT and Evaluation methods of site amplification factors based on in-situ earthquake observations, many earthquake records are used. As a result, value of SAF was calculated as an average value at each frequency point. However, earthquake records used in the calculation have variability. In this study, both variability of the GIT and variability of the SRs are quantitatively evaluated for the level 1 earthquake ground motions (design earthquake ground motions used in Japanese port area) of 10 sites, in which the SAFs were evaluated by the evaluation methods of site amplification factors based on in-situ earthquake observations. Furthermore, in order to confirm the impact of the variability on port and harbor facilities, variability of velocity power spectral intensity (PSI) and design seismic coefficient, which are indicators of the impact on port and harbor facilities, were evaluated.

We conducted a study on non-linear response estimation in unobserved stories using Augmented Kalman Filter (AKF) in the former building of the Civil Engineering and Architectural Department in Tohoku University. Firstly, we selected small earthquake records that could be considered as linear responses using the Subspace method and estimated the layer stiffness and damping ratio of each story, which is required for AKF. Then, we applied AKF to earthquake records that could be considered as non-linear responses and examined the estimation accuracy of absolute acceleration and relative displacement in unobserved stories. The results showed that AKF is effective for actual building that exhibit nonlinearity, and that the estimation accuracy is improved especially when both acceleration and displacement are used as outputs, and that L-curve method can be used to set optimal values for the process noise of the nonlinear terms that greatly affects the estimation accuracy of the nonlinear response.

After the 2011 off the Pacific coast of Tohoku Earthquake, the importance of incorporating the variety and uncertainty of the characteristics of earthquakes, including source parameters, in ground motion prediction has been re-recognized. When such prediction is used for seismic design of structures, how to treat the wide range of predicted ground motions and to determine the design ground motions depending on the required level of safety becomes an important issue. In order to appropriately evaluate the mean and the range of variation in the ground motion prediction, Monte Carlo simulation is conventionally utilized but there is a problem in that the computational demands are large. Therefore, we studied a method to calculate the ground motions based on a fault model according to the required performance level of a building with a small number of calculations. The validity of the method was confirmed for the 1923 Great Kanto Earthquake by extracting source characteristics corresponding to the mean and mean +1σof the ground motion levels and generating associated ground motions.

In the seismic isolation structure, it is important to maintain the seismic isolation device and the environment inside the seismic isolation layer on a daily basis, and to grasp the soundness of the seismic isolation layer immediately after an earthquake. Currently, inspectors and building managers directly enter the seismic isolation layer to perform inspection work, but issues have been pointed out regarding the danger of an earthquake occurring during inspection and the difficulty of technical judgment regarding soundness after an earthquake. Therefore, we developed a comprehensive monitoring system for seismically isolated buildings, using sensing and IT technology. And installed sensors for daily maintenance and management of the seismic isolation layer and a system that supports estimation of the soundness of the seismic isolation layer and the superstructure after an earthquake. We confirmed the effectiveness of the system through introduction cases.

This study examines the changes in vibration properties of a 120 m high-rise steel building 50 years after its construction. Microtremor measurements and forced vibration tests are carried out to understand the changes in vibration properties and to analyse the factors behind these changes. Vibration properties are measured for the first to third-order modes of the two translational and rotational components. The eigen periods, damping constants and mode shapes will be compared. Forced vibration tests are conducted with several forces, and the amplitude dependence of the vibration properties is evaluated. Furthermore, the influence of earthquakes and strong winds on the vibration properties are examined analytically to consider the factors that cause the changes. The experimental and analytical results showed that the primary natural period of the building increased from 2.3 s to 2.7 s, about 15%, in the 50 years after construction, and that the analytical change in natural period due to the effect of PC steel bar bracing on each floor and the actual one were generally consistent, indicating that the PC steel bar bracing may be a significant reason for the natural period increase.

Ensuring earthquake resistance in school buildings is critical for safeguarding students and teachers. Inadequately designed school buildings are at significant risk of collapse or severe damage during a destructive earthquake. This study evaluates the seismic reliability of reinforced concrete (RC) school buildings designed as moment-resisting frame systems and constructed across various regions of Afghanistan. To assess the damage probability of RC buildings under different earthquake ground motions, seismic fragility curves were generated using incremental dynamic analysis (IDA). The nonlinear frame software analysis program has been used as a research methodology to perform IDA. Six RC school buildings from the database were selected and categorized into newly designed and old-designed groups based on specific criteria, such as design details and year of construction. The results demonstrate that newly designed and constructed school buildings exhibit significantly greater resilience and are less prone to damage compared to older counterparts. The findings underscore the necessity of updating design codes and construction standards to enhance the earthquake resistance of RC school buildings. Consequently, this study proposes implementing more stringent building codes and retrofitting existing structures to mitigate earthquake risks.

Casting non-structural concrete wall elements to be monolithic with frame elements provides additional strength and stiffness to maintain post-disaster functionality. However, wall damage, such as spalling off cover concrete, may occur at relatively small drifts due to buckling of anchored longitudinal wall reinforcement. This study investigates the effects of not anchoring longitudinal wall reinforcement to decrease wall damage. As there are few experimental and analytical studies examining the lateral behavior of such elements, parametric FEM analysis was performed in this study to investigate specific conditions for which the deformation capacity increased for such elements compared to conventional detailing.

We implemented a simplified analysis method to capture the seismic behaviors of structures. In the simplified method, the soil-foundation system is replaced by a nonlinear rotational spring, a linear rotational dashpot, and linear horizontal spring and dashpot based on a simplified analysis method introduced by Anastasopoulos and Kontoroupi (2014). In order to investigate the applicability of the simplified method, we compared analysis results with 1-g shaking table tests having a building with a square-shaped spread foundation placed on soft clay soil. This comparison revealed that the simplified method could capture the response of the building during dynamic loading, although it has some limitations.

The objective of this study was to quantitatively evaluate the extent of damage to the structure of a wooden house when it is damaged by an earthquake. The accuracy of the simulation model was improved and the prediction accuracy was verified by using a data assimilation method based on quality engineering. The data assimilation was performed by using the results of small and medium excitation tests, respectively, and by performing a comprehensive simulation that considers the effects of material variation, construction error variation, and the safety factor. The data assimilation method, including parameter settings, was verified by comparing the response results of medium and large excitation using the model after data assimilation.

In this study, conventional RC partial flat wall was replaced by a CLT panel, and static loading tests were conducted using 35% scale test specimens to examine the structural performance of a RC frame with the CLT partial flat wall. A parameter for the test was presence or absence of the CLT partial flat wall, and the results were compared in terms of the parameter. The experimental investigation revealed that the presence of the CLT partial flat wall increased the strength of the RC frame. Furthermore, focusing on damage to the CLT partial flat wall, no significant damage was observed throughout the loading, unlike those to conventional RC partial flat walls showing shear failure at small deformations.

Hydraulic model experiments using a scaled model were conducted to evaluate the response of the seismically isolated building against tsunami. The scale of the model was 1/150. The experimental parameters included the installation angle of the model and the reproduction of the isolated layer displacement or not. The results showed that the maximum hydrodynamic force is roughly proportional to the width of model across the tsunami flow, and that the hydrodynamic force doesn't increase sharply when the installation angle is 45 degrees. Both the hydrodynamic force and buoyancy force increased, when the displacement of the isolated layer was reproduced.

Property of energy/displacement conservation is a simple method for estimating complex behavior of structures during earthquakes. Response obtained by property of energy/displacement conservation and that obtained by nonlinear dynamic analysis are different, but this difference has not been fully investigated. In this study, using many seismic wave observation records with large amplitude, difference of response evaluation was discussed. As a result, property of energy conservation tends to overestimate the response of structures with long natural period, while property of displacement conservation tends to underestimate the response of structures with short natural period. Furthermore, accuracy of property of energy/displacement conservation decreases when it applies to structures with natural period which corresponds to maximal or minimal Fourier amplitudes of the seismic wave.

From 1999 to the present, earthquake observations have been carried out on super high-rise RC structures. We examined the predominant frequency and damping ratio of the building using observation records. It was showed that the predominant frequency decreased and the damping ratio increased after a large earthquake. Both the predominant frequency and the damping ratio depend on the maximum relative displacement of the roof floor to the basement floor. For the observation records, A bending shear model used in the seismic response analysis at the time of design was set at the base of the model with a rotating spring and a dashpot based on the thin layer method.

This study demonstrates the use of multi-temporal LiDAR data to observe damage situations and to monitor recovery process in Atsuma Town, Hokkaido, Japan, after the 2018 Hokkaido-Eastern-Iburi earthquake. By taking the difference of the Digital Surface Models (DSMs) acquired from the LiDAR data in pre- and post-event times, landslides and damage to buildings and infrastructures were extracted and the results were compared with aerial optical images and the collapsed and accumulated soil areas from visual inspection. From the DSM difference between the post-event times, the recovery activities from the earthquake damage were also recognized in the 3D form.

We considered the possibility of earthquake observation by smartphones that people have on a daily basis. A hands- on experiment was conducted using “Jishin the Vuton”. At that time, Experienced person experienced the seismic motion with the “Jishin the Vuton” with three smartphones, one in my neck strap, one in my pocket, and one I held in my hand. We examined and considered the records obtained. After filtering the obtained records, we calculated the maximum value and the instrumental seismic intensity. We found that the value observed with a smartphone was slightly larger than the value we experienced. It was found that there is a possibility that the numerical value reflects the actual shaking.

This paper reports on examples of building damage caused by fault displacement from past active fault zone earthquakes and effective fault displacement countermeasures. Conventional fault displacement countermeasures have generally avoided active faults. However, recurrence period of active faults is extremely long (several thousand years or more), and it is generally difficult to accurately determine in advance the location and amount of fault slip and fault types such as transverse and longitudinal displacement on the scale necessary for building design. On the other hand, studies of recent damaging earthquakes (e.g., the 1999 Taiwan Chi-Chi earthquake and the 2016 Kumamoto earthquake) have shown that buildings with earthquake-resistant design can significantly reduce damage even directly above a surface fault rupture. For this reason, a variety of fault displacement measures have become available in recent years and have been implemented in building construction and retrofitting.