The 1923 Kanto earthquake caused enormous damage to the Tokyo metropolitan area. In order to understand the intensity of ground motion during the Kanto earthquake, isoseismal maps of the earthquake are collected. Then, they are classified into the following categories: 1) preliminary one, 2) one based on field surveys, 3) one based on damage to wooden houses, and 4) one based on the seismic intensity reported by the Central Meteorological Observatory. The characteristics and differences of the maps excluding the preliminary ones are summarized. Then, the relationship between seismic intensity and collapse rate of wooden houses was reviewed and the area of seismic intensity VI was reexamined.

Towards probabilistic seismic hazard assessment based on ground motion time history data, we develop a probabilistic model capable of directly generating three-component acceleration time history data of ground motion. Recently, generative models using deep learning have attracted significant attention due to their high performance. In this paper, we employed a deep generative model called Generative Adversarial Networks to learn from the strong-motion records of crustal earthquakes. The model after training is capable of generating ground motion time history data consistent with the conditions of magnitude and distance, and is a probabilistic model approximating the distribution of learned database. Furthermore, it is shown that the distribution of the generated ground motion generally corresponds to the existing ground motion prediction equations.

Rubber bearings are now commonly used to prevent seismic damage to bridges, but they can be destroyed in huge earthquakes. Even if it is not destroyed, it may suffer internal damage, however, it is difficult to detect internal damage because it is covered by coated rubber. This study verified the propagation of elastic waves in a laminated rubber bearing by numerical analysis, and used the data to detect damage using a machine learning anomaly detection technique. The results showed that the damage inside the rubber bearing can be detected using the One-Class Support Vector Machine anomaly detection method.

Furumura et al. (2023) trained Convolutional Neural Network models to automatically digitize waveforms in the JMA strong-motion seismograms. To confirm the validity of the model, automatically digitized data of the smoked-paper strong-motion seismograms of the 1940 Kamui-Misaki-Oki Earthquake, which were not used for model training, were compared with manually digitized data. The comparisons showed that although some data correction was required, the automatic data were in good agreement with the manual data, and that this method can significantly improve the efficiency of analog record digitization.

Structural method to join RC-column and S-beam without the S-beam penetrating the RC-column has been developed by use of high strength rebars. FE analyses are conducted for a variety of previous test specimens to investigate the applicability of the analysis for the structural method. It is found that FE analysis can reproduce the nonlinear behaviors of the test specimens. Furthermore, Numerical studies by FE analysis are performed to evaluate structural performance of exterior side joint under tensile axal force and interior joint with steps in beam.

This paper presents a static cyclic loading test of beam-column joint specimens made with H-section columns and beams. The features of the structures are; 1) beams and columns are connected by fillet welds, 2) No stiffeners are provided in the panel zone. Specimens are provided 2.5mm (FW25), 5.0mm (typical length in old Japanese construction, named as FW50), and 7.5mm (FW75) of the leg length, respectively. In addition, FW75_CPL specimen is tested which has cover plate for making H-section square. Test results showed that higher seismic performance when leg length increased and cover plate existed.

When constructing additional reinforced concrete seismic walls to existing buildings, mortar is sometimes required instead of concrete, which does not impair the habitability and the usability of the building during construction. However, compared to concrete, mortar has greater drying shrinkage and different shear stress transfer characteristic at the crack interface, so the performance of reinforced mortar seismic walls differs from that of using concrete. In this study, a static loading test and nonlinear finite element analyses were conducted in the three-dimensional stress field simulating the test to establish the method for evaluating the structural performance of reinforced mortar walls. As a result, the hysteresis behavior of the reinforced mortar seismic wall measured in the experiment could be properly evaluated by the analyses.

In the seismic design of secondary systems (SS) such as nonstructural components, the effect of torsional vibration of structural frames is not explicitly considered. Although torsional vibration may increase the inertia forces of SS, the degree of amplification and governing parameters have not been sufficiently clarified yet. In this paper, floor response spectra are investigated for single-story asymmetric buildings to understand the effect of torsion on SS. The results show that the maximum value of floor response spectrum becomes larger than that without the effect of torsion as the eccentricity ratio increases. But when the eccentricity ratio exceeds 0.1, the maximum value is almost constant at about 1.2 times larger than that without eccentricity.

Tsunami evacuation towers play an important role in emergency evacuations in coastal regions. The placement of the evacuation towers has been determined based on the worst-case tsunami scenario. However, the tsunami intensity and corresponding arrival time to coastal regions should be estimated taking into consideration uncertainties associated with fault movements. It should be investigated whether the placements of evacuation towers based on the worst-case tsunami scenario can minimize the tsunami casualties. This paper presents a novel framework for optimizing the placement of evacuation towers based on the risk associated with tsunami casualties under the constraint of budget. As an illustrative example, the proposed method is applied to a coastal region affected by the anticipated Nankai Trough earthquake. The effect of the tsunami hazard assessment method on the optimal placement of evacuation towers is discussed.

We proposed the restorability evaluation method for railway structures. In this method, all earthquake motions expected within the design service life are used as the design earthquake and the recovery time after an earthquake is used as the verification index. We also proposed more practical method in which structural conditions with the same recovery time are expressed as a nomogram by performing calculations under various conditions in advance. By using the proposed method, it is possible to design structures that can be easily recovered in the same procedure as the conventional seismic design, and it is expected to shorten the recovery time after an earthquake.

Differences in liquefaction strength due to variations in grain size can be explained in relation to volume change characteristics. However, the differences in grain size also affect the soil permeability, increasing the apparent liquefaction strength as the partial drainage effect. A pore pressure generation model predicts the excess pore pressure using the unique index of volumetric strain, thereby enabling the consideration of both volume change characteristics and partial drainage effect in a unified manner. In this study, triaxial tests were conducted using sands of different grain sizes, and the liquefaction strength was evaluated using the model. From the triaxial tests and the predicted results, it was confirmed that the differences in liquefaction strength could be explained by the plastic volumetric strain and elastic modulus of the sand. Furthermore, a series of centrifuge tests was conducted to verify the increase in apparent liquefaction strength due to the partial drainage effect. The increase in liquefaction strength could be evaluated based on the volumetric strain due to the partial drainage.

Liquefaction assessment is necessary for the seismic design of nuclear power plants even for Pleistocene sand, conventionally regarded as non-liquefiable soil. In this paper, a series of undrained cyclic hollow torsional tests, centrifuge model tests, and numerical analysis on open channel bearing ground were conducted using a simulated Pleistocene sand, which imitates liquefaction characteristics of natural Pleistocene sand by adding cement to sandy soil. The simulated Pleistocene sand imitated the failure characteristics of the natural Pleistocene sand; shear failure occurred before the excess pore water pressure ratio reached 1. The total stress analysis could reproduce the acceleration and axial strain observed in the centrifuge model tests.