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Tomiichi UETAKE, Kazuhito HIKIMA, Akihiro SHIMMURA, Masatoshi FUJIOKA
2025 Volume 25 Issue 1 Pages
1_1-1_12
Published: 2025
Released on J-STAGE: January 15, 2025
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We investigated the wave propagation characteristics of the seismic waves from small earthquakes near the site, using the dense surface array, vertical arrays, and deep-borehole observations in the Kashiwazaki-Kariwa nuclear power station. We confirmed that the initial P- and S-wave velocities pass through the site and that the time it takes to pass through the vertical array is related to the angle of incidence on the site. In the M2 class event’s waveforms in deep-depth records, the reflected waves from the ground surface are unclear, and no clear later arrivals can be found. This is because of the upper layers' scattering and absorption of high-frequency waves. For the M4 class events, in addition to reflected waves from the ground surface, there were clear later arrivals after 6 to 7 s from initial S-waves in event traces. Since these waves propagated as body waves in upper layers, we assumed that these waves were waves reflected from seismic bedrock. Using the surface array and deep borehole data, we also recognized the locally trapped surface waves in the upper layers. Three-dimensional earthquake observation is effective for understanding the propagation characteristics of seismic waves.
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―A Case Study at the KiK-net Choshi-naka Station―
Masashi AOKI, Yu YAMAMOTO, Yasuo UCHIYAMA, Nobuo TAKAI
2025 Volume 25 Issue 1 Pages
1_13-1_24
Published: 2025
Released on J-STAGE: January 15, 2025
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In seismic motion evaluation, it is important to consider the variation due to the uncertainty of the set model. Ground amplification characteristics are often evaluated based on the ground structure model estimated by inverse analysis targeting the Surface/Borehole Spectral Ratio (SBSR). At an observation point, horizontal 2-component seismic motion records can be obtained, but there may be differences in the SBSRs evaluated for each direction. In this paper, the authors quantitatively evaluated the variation of the SBSR calculated for each direction of the horizontal component, and analyzed the relationship between the variation of the SBSR and the incident wave field, targeting the KiK-net Choshi-naka station. As a result, it was qualitatively shown that the variation of the SBSR is affected by the arrival direction of the seismic wave, and is due to the directional dependence of the SBSR caused by the irregular ground. In addition, we examined the effect of ground irregularity on the SBSR by the finite element method, and showed that the horizontal component of the SBSR varies due to irregular ground even in the case of vertical incidence.
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Yoshinori TOKIZANE, Hiromitsu NAKAMURA, Yasushi KOMARU, Hiroyuki FUJIW ...
2025 Volume 25 Issue 1 Pages
1_25-1_37
Published: 2025
Released on J-STAGE: January 15, 2025
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When conducting seismic risk assessment for portfolios distributed over a wide area, it is necessary to consider the spatial correlation of ground motions. In addition, in order to link risk assessment to disaster prevention measures, it is necessary not only to obtain a E.P. (Exceedance Probability) curve that represents the relationship between damage and exceedance probability, but also to indicate the distribution of ground motions that constitute the E.P. curve. In this study, based on the ground motion generation method by mode synthesis by previous studies. In this method, the trend component is replaced by a GMPE and mode-synthesized using the adjusted singular value, so that the mean value and the level of variation of the generated seismic motion are approximated to the observed record.
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Kosuke KAWARAI, Michio OHSUMI
2025 Volume 25 Issue 1 Pages
1_38-1_49
Published: 2025
Released on J-STAGE: January 15, 2025
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Structures such as road bridges are designed considering various uncertainties. In design of road bridges using the partial factor method, uncertainties which can be evaluated probabilistically are considered by partial factors. On the other hand, uncertainties that are difficult to evaluate probabilistically are treated in various ways in the design process. The level of reliability required for the measures to deal with uncertainties other than those expressed by partial factors is not clear. Therefore, to improve the accountability of treatment of uncertainties and to deal with uncertainties more reliably and efficiently in the design of road bridges, this study discusses uncertainties in the design of road bridges and examines a framework for treatment of uncertainty in seismic design.
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Genta GOTO, Ryota TAKAHARA, Keita UEMURA, Yoshikazu TAKAHASHI
2025 Volume 25 Issue 1 Pages
1_50-1_63
Published: 2025
Released on J-STAGE: January 15, 2025
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Columns with a height of more than 30 m are used for bridges in mountainous areas. In order to reduce the load on the foundation and construction cost, hollow-section columns are used to reduce the dead weight of the columns. Previous studies have indicated that damage to walls subjected to compression in hollow-section piers is correlated with the position of the neutral axis. In this study, cyclic loading tests were conducted using a large RC hollow-section specimen 1/5 scale of an actual pier to investigate the effect of the neutral axis position on the fracture behavior of the existing RC hollow-section specimen. The effects of changing the position of the neutral axis by changing only the axial stress or only the reinforcement are discussed on the failure behavior.
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Kazunori WADA, Kimitoshi SAKAI, Yoshikazu TAKAHASHI
2025 Volume 25 Issue 1 Pages
1_64-1_77
Published: 2025
Released on J-STAGE: January 15, 2025
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In recent years, a quantitative evaluation method for anti-catastrophe has been proposed. However, this is still conceptual, and it cannot be said that an evaluation method based on design practices has been established. Therefore, we focus on redundancy, which is one of the performance items of anti-catastrophe, and propose a quantitative evaluation method of redundancy for railway bridges and viaducts. In this method, the structural redundancy is evaluated from both perspectives, “margin” that means the displacement leading to collapse against the design limit displacement and “parallelism” that means the change in the margin when the column member disappears. And the structural analysis confirmed the validity of the method. By using this method, it becomes possible to explicitly consider redundancy in seismic design, diagnosis, reinforcement, etc.
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Shinsuke AKAMATSU, Masahiro HATTORI, Yoshiki TANIGUCHI, Miki NISHIMURA ...
2025 Volume 25 Issue 1 Pages
1_78-1_89
Published: 2025
Released on J-STAGE: January 15, 2025
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Monitoring measurements have been conducted on an integrated columns by multiple steel pipe applied to actual bridges to verify that the pier behave according to the concept assumed in the design. In this measurement, the response is measured for both ordinary conditions and small earthquake conditions. This study proposes a method for verifying the performance of an integrated column by multiple steel pipe using the measured data, and evaluated the performance of the piers using the measured data obtained so far. For ordinary conditions, the measured data were used to verify that the behavior of the piers was as assumed in the design, and for small earthquake conditions, the validity of the analysis model was verified by reproduction analysis using observed waveforms.
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Eriko BAMBA, Toshiyasu UNNO, Tatsuya EMORI, Kazuhiko UENO
2025 Volume 25 Issue 1 Pages
1_90-1_101
Published: 2025
Released on J-STAGE: January 15, 2025
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In recent years, it has been observed that the ground in areas affected by natural disasters is often composed of crushable soils. This study focuses on soil samples with crushable properties, examining the strength and crushability of soil particles. To investigate the crushing strength of individual soil particles and to explore the relationships between particle breakage and the static shear strength and liquefaction resistance of the soil, we conducted single-particle breakage tests, monotonic shear tests using a hollow torsional apparatus, and cyclic shear tests. In the monotonic shear tests under undrained conditions, we confirmed that the behavior of the effective principal stress varies depending on the crushing strength obtained from the single-particle breakage tests and the degree of particle breakage. The results of the cyclic shear tests indicated that soil samples with higher individual particle strength tend to develop excess pore water pressure and shear strain within fewer cycles when the amplitude of the generated shear strain is less than 7.5%. However, as the number of load cycles increased and the amplitude of the generated shear strain exceeded 7.5%, leading to more significant liquefaction, differences in the development of shear strain were observed between soil samples containing stronger individual particles and those containing weaker individual particles.
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Tomoki YASUHARA, Gaku SHOJI
2025 Volume 25 Issue 1 Pages
1_102-1_112
Published: 2025
Released on J-STAGE: January 15, 2025
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In the 2011 Tohoku earthquake, we had many damages to long-period infrastructures which natural period of more than 1 second, especially located in the Tokyo Bay area. Therefore, it is necessary to clarify the seismic-wave characteristics that cause the seismic damage of long-period bridges. We analyzed the characteristics of site waves on the engineering base for the 83 sites under the road networks using the finite difference method with fourth-order spatial and second-order temporal accuracy using a discontinuous grid.
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Kota OSASA, Keisuke KATO, Yuya TAKASE, Tadayoshi NAKASHIMA
2025 Volume 25 Issue 1 Pages
1_113-1_122
Published: 2025
Released on J-STAGE: January 15, 2025
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Japan frequently experiences major earthquakes. Damage assessment of buildings, such as the Emergency Safety Check, is required for reconstruction efforts. Currently, damage assessment is performed by investigators through field surveys. In this study, the authors attempted to propose the assessment using AI and IoT for more effective and faster assessment. First, the deep learning model was constructed using the images of damaged buildings from previous earthquakes. Subsequently, the authors created a damage map by using the results of the damage assessment of buildings by the learning model and the aerial images taken by a drone in Suzu, Ishikawa; and then, the authors compared it with the visual assessment. The results showed that the model was able to adequately determine the degree of total destruction, however the model tended to underestimate the degree of semi-destruction.
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Shusaku INOUE, Kazuki WATAI, Takayuki SONE
2025 Volume 25 Issue 1 Pages
1_123-1_131
Published: 2025
Released on J-STAGE: January 15, 2025
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This study presents a simplified method for analyzing pool sloshing during earthquakes, using frequency response analysis. It starts with a linear formula for water surface movement, extends it to include damping effects, and derives response functions for water level and pressure. By comparing with numerical fluid analysis, the study confirms the accuracy of this approach in calculating sloshing for different acceleration inputs. This method offers a convenient alternative to complex simulations for studying pool sloshing behavior during earthquakes.
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Masahiro OHBUCHI, Ataru FUJII, Mutsuhiro YOSHIZAWA, Yoshiyuki SATO, Sh ...
2025 Volume 25 Issue 1 Pages
1_132-1_141
Published: 2025
Released on J-STAGE: January 15, 2025
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Considering the desirability of constructing disaster base buildings in areas with a low risk of being affected by the same disaster as the main base, this paper proposed a conditional seismic hazard map that assumes the seismic intensity at the main base exceeds a certain level. We evaluated areas with a low probability of simultaneous impact on main bases and disaster base building using conditional seismic hazard maps for Tokyo, Osaka, and Nagoya. As a result, if the location were to be situated near Chiyoda Ward, Tokyo, the area around Nerima Ward would be a candidate location, while the western part of Kobe City was selected as a candidate location for central Osaka. For Nagoya, areas near Komaki City and Nagakute City were selected as candidate locations.
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Takaya NAKAMURA
2025 Volume 25 Issue 1 Pages
1_142-1_152
Published: 2025
Released on J-STAGE: January 15, 2025
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Existing reinforced concrete (RC) buildings with brittle columns may be hazardous in the event of an earthquake. To effectively plan building evacuations, it is important to determine how much time takes for such buildings to heavy damage. Thus, we conducted a dynamic analysis using test results to examine the ultimate time of RC buildings that were designed according to old Japanese codes. The ultimate time was defined as the time between the appearance of cracks and ultimate drift. The ultimate drift was a lateral drift when the lateral load decreased to 80% of the maximum strength.
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Taiki HAGIWARA, Takashi OHKUBO, Hitoshi NAGUMO
2025 Volume 25 Issue 1 Pages
1_153-1_163
Published: 2025
Released on J-STAGE: January 15, 2025
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Seismic hydrodynamic pressure, which causes rapid water pressure fluctuations during earthquakes, has been observed in agricultural pipelines. Examples of seismic disasters include detachment of a pipe at a curved section and damage to an air valve, which are caused by water pressure fluctuations during an earthquake. It has not been fully reflected in the design of agricultural pipelines and earthquake countermeasures at present because there have been few cases of actual measurements of seismic hydrodynamic pressure on pipelines. In this study, we attempted to evaluate the relationship between acceleration and water pressure fluctuation by numerical simulation and frequency analysis using FFT for the measured seismic hydrodynamic pressure in an agricultural pipeline.
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Junji HAMADA, Takehiro OKUMURA, Kazutomi NAKANE
2025 Volume 25 Issue 1 Pages
1_164-1_174
Published: 2025
Released on J-STAGE: January 15, 2025
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This paper presents a case of seismic observation of a piled raft foundation for a 10-story RC building adjacent to a pile foundation building. The acceleration of the first basement floor, axial strain and bending strain of the pile, earth pressure and water pressure beneath the raft around the piles were measured. Seismic observations started on July 17, 2016, and seismic events including M 7.4 have been observed about 380 times in site. The relationship between the bending strain of the pile and the inertia force of the building, the relationship between the axial strain of the pile and the bottom earth pressure, etc., has been investigated. The difference between the behavior of the foundation during the period including main shock in which inertial force of the building were dominant and that during the subsequent period was clearly observed.
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YuTing CHOU, Thinzar Yadanar, Fumiaki NAGASHIMA, Shinichi MATSUSHIMA
2025 Volume 25 Issue 1 Pages
1_175-1_185
Published: 2025
Released on J-STAGE: January 15, 2025
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Subsurface structure model is indispensable in ground motion estimation. There are various methods to estimate the subsurface structures above the seismic bedrock. One of them, velocity model identification based on horizontal-to-vertical spectral ratios of microtremors (MHVRs), is often utilized due to its convenience. However, one-dimensional subsurface structure is often assumed when analyzing MHVRs although directional dependence can be seen in some of the observed MHVRs. The directional dependence is assumed to be related to the lateral heterogeneity of the subsurface structure but investigation of the effect of heterogeneity of subsurface structure on MHVRs is still insufficient. In this study, we perform microtremor measurements around Gokasho, Uji, Kyoto, and examine the effect of lateral heterogeneity on the directional dependence of MHVRs and phase velocities obtained from microtremors. As a result, the spatial variation of the peak frequency and the directional dependence of the amplitude of MHVRs correspond to the inclination of the Tamba group, which is the bedrock layer in the study area. In addition, it was found that the phase velocity of the Rayleigh wave is dependent of the direction of the back azimuth and the phase velocity propagating from the south is slower compared to those from the west for the frequency of 1.2 Hz and it is assumed that the velocity is slower in this frequency range in the study area.
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Kenichi KATO, Tetsushi WATANABE, Yusuke TOMOZAWA, Kiichiro NOJIRI
2025 Volume 25 Issue 1 Pages
1_186-1_199
Published: 2025
Released on J-STAGE: January 15, 2025
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When the fault area spreads within the seismogenic layer, earthquake faults appear on ground surface. Quantifying the magnitude of earthquakes at which surface faults appear is an important issue for strong ground motion prediction. We quantified the occurrence rate of surface faults against both JMA magnitude and Moment magnitude by the model function derived from the newly constructed data by combining Takemura (1998) and recent earthquakes. The occurrence rates of surface faults for large earthquakes for which there is little data were supplemented by overseas earthquakes and theoretical studies using characterized source models.
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Takehiro OKUMURA, Junji HAMADA
2025 Volume 25 Issue 1 Pages
1_200-1_211
Published: 2025
Released on J-STAGE: January 15, 2025
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The behavior of piled-raft foundations supporting buildings on soft ground is complex because they are subjected to the superstructure's inertial forces, overturning moments, and ground deformation during large earthquakes. In this study, we compared experimental cases with and without superstructures using centrifuge model tests of piled raft foundations on soft clayey ground. The results showed that, compared to the case without a superstructure, the case with a superstructure experienced a larger overturning moment, causing the pile head to rotate. Notably, despite the building inertial force being approximately three times larger in the case with a superstructure, the bending moment at the pile head was smaller than the case without a superstructure.
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Keisuke KOJIMA, Kazuki MATSUMOTO, Michihiro OHORI
2025 Volume 25 Issue 1 Pages
1_212-1_221
Published: 2025
Released on J-STAGE: January 15, 2025
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This study examines the effectiveness of estimating surface wave characteristics based on six-component observations, including three translational and three rotational components. Assuming that Rayleigh and Love waves propagate from the same direction, the arrival direction is determined based on the rotation velocity around the two- horizontal axis. The phase velocity of the Rayleigh wave and the Love wave can be determined by taking the ratio of the translational acceleration to the rotational velocity. Through the analysis of single-point six-component observation data of artificial vibration consisting of Rayleigh and Love waves propagating as plane waves from arbitrary directions, it is confirmed that the direction of propagation of surface waves, amplitudes of Rayleigh and Love waves at each frequency, and phase velocity can be accurately estimated. The proposed procedure is also applied to strong-motion observation data, and the possibility of obtaining the phase velocity of surface waves is demonstrated.
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Bohan WANG, Yoshiyuki MOHRI, Hidekazu TAGASHIRA, Akira IZUMI, Tadatsug ...
2025 Volume 25 Issue 1 Pages
1_222-1_231
Published: 2025
Released on J-STAGE: January 15, 2025
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The seismic damage of reservoir embankments is due to weakening of the embankment soil during earthquake. To analyze the seismic behavior of embankments, we conducted centrifugal shaking tests on a reservoir embankment model under water storage conditions, followed by elasto-plastic dynamic finite element analyses. As a result, shear failure and deformation of the embankment as well as dynamic response of the model were evaluated by the analysis considering cyclic stress and strength reduction characteristics of the embankment according to the number of cyclic shear stresses. Furthermore, the effectiveness of partial seismic reinforcement measures for the reservoir embankment is also reported.
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Noriaki SENTO
2025 Volume 25 Issue 1 Pages
1_232-1_238
Published: 2025
Released on J-STAGE: January 15, 2025
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In the March 16, 2022 off the coast of Fukushima Prefecture earthquake, five different types of quay walls were damaged by the strong motion of the seismic intensity of 6 upper at Soma Port in Fukushima Prefecture, and the damage was different for each type of structure. This paper compares the horizontal displacement of the quay wall and the subsidence behind it for each type of quay wall based on the results of post-earthquake surveys. The results showed that the steel pipe sheet pile quay wall had the smallest displacement and was the most tenacious structural type. On the other hand, re-liquefaction was observed where areas that liquefied in 2021 liquefied again during the 2022 earthquake. Therefore, laboratory tests were conducted on the sand eruptions collected in the wharf to clarify their physical properties.
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Kentaro KASAMATSU, Tetsushi WATANABE, Fumino SUZUKI, Kazuhito HIKIMA, ...
2025 Volume 25 Issue 1 Pages
1_239-1_249
Published: 2025
Released on J-STAGE: January 15, 2025
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We conducted dynamic rupture simulations of crustal earthquakes at the seismic moment between 1017 and 1021 Nm using heterogeneous fault models with random initial shear stresses to investigate characteristics of strong ground motions near the faults. After the validity of the simulations was confirmed through comparisons with the previous relation between seismic moment and rupture area, we showed the distribution between earthquake magnitude and maximum ground motions with maximum velocities and response spectra. We found that the maximum ground velocities of the strike-slip faults converge to a constant value with the seismic moment of 1020 Nm when the averaged stress drop is constant. On the other hand, the amplitudes of reverse faults increase in proportion to the earthquake magnitude and do not reach a constant value. We also evaluated the scaling law for the maximum amount of slip on the ground surface and the fault length using the average stress drop as a variable.
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Ryo MAJIMA, Taiki SAITO, Shigeki SAKAI, Yasuo YAMASAKI
2025 Volume 25 Issue 1 Pages
1_250-1_260
Published: 2025
Released on J-STAGE: January 15, 2025
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Pulley damper ceiling system is a new damping system that employed a vibration control system using block and tackle proposed by the authors. The pulley amplification mechanism allows to improve the energy absorption of the connected damper. Unidirectional shaking table tests were initially conducted to verify the ceiling response reduction effect and the applicability of the amplification mechanism. The test results demonstrated that the proposed system absorbed more than 90% of the input energy, and reduced the displacement and acceleration response to half that of the undamped specimen. Besides, the influence of the bolt support conditions and calculations formula for natural period of suspended ceiling were analyzed. Furthermore, the torsional behavior of ceiling panel was investigated through bidirectional excitations test. It was successfully confirmed that no torsional response was observed and the response in each direction was independent.
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Daiki NAKAMIZO
2025 Volume 25 Issue 1 Pages
1_261-1_272
Published: 2025
Released on J-STAGE: January 15, 2025
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In performance-based design, structural engineer needs convenient design formulae of response drift of an elasto-plastic structure. In the study, we consider the design formulae in case of total input energy to a structure is constant and the equivalent reputation number is variable. The verifications of equivalent linearized models and elasto-plastic models in the study are analysed considering the level of seismic design load of the Building Standard Law of Japan.
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Makoto ISHIMARU, Masahiro SAWATSUBASHI, Kenji HIRAGA, Ikki KATO, Takaa ...
2025 Volume 25 Issue 1 Pages
1_273-1_283
Published: 2025
Released on J-STAGE: January 15, 2025
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Landfill ground consisting of rock debris has been treated as ground that is resistant to liquefaction. However, in recent years, the number of cases requiring stability evaluation that considers the effects of liquefaction is increasing due to the increase in design seismic ground motion. In this study, we conducted a centrifugal model test and its numerical simulations on the seismic behavior of rock debris under conditions in which a 10 m-high cement-improved embankment was constructed on a 15 m-deep rock debris landfill ground. In the numerical analyses, two types of effective stress analysis codes, one for undrained conditions and the other for drained conditions, were used. As a result, it was clarified that the effective stress analysis method of the drainage condition was more consistent with the test results, because rock debris had a greater effect on permeability and dilatancy than sand.
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Hidetoshi KASUGAI, Yoshiaki HISADA, Shinya TANAKA
2025 Volume 25 Issue 1 Pages
1_284-1_294
Published: 2025
Released on J-STAGE: January 15, 2025
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In recent years, Japan has accumulated a vast amount of earthquake observation records due to the strong-motion network, and the Empirical Green's Function Method (EGF method) is expected to be more effectively utilized. The EGF method has been used mainly for short-period body waves, but has not been used for broadband seismic motions including subsequent surface waves. It should be noted that the amplitude characteristics of short-period entity waves with random characteristics and long-period surface waves with coherent characteristics differ greatly due to the superposition of element waveforms. In this study, we reproduced broadband seismic motions including surface waves for the 2000 Tottori-ken Seibu Earthquake, for which aftershock records are abundantly observed, and investigated points to be considered when synthesizing waveforms. Two elemental earthquakes of different sizes were selected, and four source models were used for simulation, with different assignments to the two Strong Motion Generation Areas (SMGA) and different rupture propagation types. In order to synthesize long-period subsequent waves at distant stations, it is necessary to use elemental earthquakes with large scale and good signal-to-noise ratio, and Case with a small number of SMGA divisions was also considered. As a result, it was confirmed that different types of ruptures on the fault plane and different propagation directions cause different time differences in waveform synthesis, especially large differences in the amplitude of long-period subsequent waves.
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Kazuki KARIMAI, Wen LIU, Yoshihisa MARUYAMA
2025 Volume 25 Issue 1 Pages
1_295-1_304
Published: 2025
Released on J-STAGE: January 15, 2025
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In this study, the authors developed a machine learning model to predict land subsidence caused by liquefaction resulting from an earthquake, with the aim of improving liquefaction hazard maps. A numerical model for predicting land subsidence due to liquefaction using XGBoost (eXtreme Gradient Boosting), which is one of the ensemble machine learning methods, was developed based on the results estimated by the Nankai Trough Earthquake Model Examination Committee. Additionally, the numerical model was applied to estimate the land subsidence in Chiba Prefecture, where liquefaction was extensively observed after the 2011 Great East Japan Earthquake. The results showed a geotechnically valid map of expected land subsidence because significant subsidence was observed in the areas where liquefaction conditions were met.
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