Earthquake-triggered landslides are known to exhibit unique regional characteristics that can cause extensive damage to the environment, resulting in a significant loss of life and property. This study aims to comprehensively investigate the role of ground motion time histories in shaping the unique distribution of coseismic landslides during the 2018 Hokkaido Eastern Iburi earthquake. Despite the similar geological and geomorphological conditions on the northern and southern sides of the epicenter, landslide density was notably higher on the northern side. In our workflow, we conducted nonlinear dynamic finite difference simulations of slope stability to reproduce the actual landslide distribution pattern using synthetic waveforms. We discuss the controlling role of ground motion time histories on these coseismic landslides. The study reveals that differences in phase components were responsible for the varying deformation processes of slopes under seismic loading, ultimately leading to the observed differences in landslide distribution. Moreover, the study emphasizes that energy-based seismic intensity measures carry greater significance than amplitude-based intensity measures because they consider the entire ground motion time histories rather than focusing solely on peak values at specific moments. The proposed method outlined in this study can be applied to regional landslide hazard analysis and risk assessment for future earthquakes.

A post investigation of landslides induced by strong earthquake events in recent years shows that near-fault pulse-like ground motions have a considerable impact on slopes. Accurate evaluation of the stability of slopes under near-fault earthquakes has become a crucial issue in seismic-prone areas. Permanent displacement is widely recognized as an effective index for evaluating the stability of slopes. In order to explore what extent the pulse component of pulse ground motion plays a role in slope instability, three synthetic wavelets proposed by Baker, Chang and Zhang were used to obtain the pulse-like components of ground motions and residual ground motions. A statistical distribution comparison between the displacement of the original ground motion record, the synthetic wavelet, and the residual ground motion records-induced can help determine whether the most damaging parts of the record are the pulse-like components and whether the synthetic wavelet accurately captures this damaging behavior. Specifically, for both rigid and flexible slopes, this comparison provides insight into the relationship between the pulses contained in the ground motion and the size of permanent displacement. The results reveal that, in some cases, the permanent displacement of the slope under pulse-like ground motion is similar to that of the original ground motion. This suggests that the pulse component in near-fault pulse-like ground motion is a significant factor in causing slope instability.

Global climate change is leading to prolonged periods of low rainfall followed by intense thunderstorms, causing severe droughts in vital water resources like rivers and reservoirs. Additionally, heavy rainfall events are causing landslides and significant damage in many countries. Dams and artificial water reservoirs are crucial in mitigating these risks. Given the limited availability of suitable sites for constructing new reservoirs, existing dams must be safeguarded, although they also pose seismic vulnerability risks due to the uncontrolled release of water. Therefore, it is crucial to assess the seismic performance of earth dams and plan rehabilitation works accordingly. This paper focuses on the coupled hydro-mechanical modelling of the seismic response of a zoned earth dam. The model was calibrated using results from a geotechnical centrifuge test, simulating the impoundment phase and applying increasing levels of seismic input. The comparison between the predicted and observed behaviour demonstrated the efficacy of the finite element (F.E.) model in accurately capturing the key characteristics of the response exhibited by this complex geotechnical system when subjected to dynamic loads.

Large earthquakes cause slope instability in hilly areas, resulting in landslides. Landslides can potentially kill people and seriously harm infrastructure like highways and railroads. Because of the severity of the immediate and long-term effects of landslide destruction, more reliable methods of failure estimation are required. In this study, a unique approach is used to calculate the likelihood of the safety factor and permanent displacement of natural slopes under earthquake shaking. The proposed approach was constructed using probabilistic modeling of landslide instability based on the Bayesian Network technique. First, the pseudo-static factor of safety was computed, considering it an uncertain parameter. Then, the permanent displacement of failure mass was estimated through probabilistic analysis considering the effect of critical and peak horizontal acceleration. In the process of probabilistic analysis, soil and slope properties (cohesion, friction angle, unit weight, slope angle, and failure depth) and peak horizontal acceleration were considered as random variables distributed as normal and exponential functions, respectively. To illustrate the applicability of the proposed approach, a hypothetical infinite slope was adopted from past literature. The results showed that due to the event of an earthquake, the slope might experience permanent displacement. Finally, based on the variation of permanent displacement, the likelihood of landslide occurrences was estimated. Validation of the study was established by comparing the outcomes with the results obtained using the analytical joint probability method. The methodology presented in this study would lead to an estimation of landslide failures by taking uncertainties into account, which would increase the safety of city dwellers.

In this study, a series of centrifuge shake table tests were conducted to investigate the damage process and the failure mode of embankments during earthquakes. We also examined the safety limit value of embankments against sliding failure. The results showed that the embankment with a slope of 1:1.5, which is the standard slope gradient in Japanese railways, showed shaking-down settlement without sliding failure even after repeated shaking. On the other hand, embankments with a slope steeper than 1:1.5 showed sliding failure during shaking. In addition, we applied a proposed method for verifying the safety performance of embankments during earthquakes to these experimental results and confirmed that the safety against sliding failure can be evaluated by comparing the shear strain at the toe of the slope with the damage level obtained from the deformation characteristics of the embankment material.

In at least two out of the three recent major failures of tailings dams, two in Brazil and one in Australia, where incipient failure due to other causes has been evident, the occurrence of small earthquakes or mine blasts immediately prior to the failure has been essentially ruled out as the principal trigger. This is in accord with the widespread belief that very short period / higher frequency motions are not “seen” by large earth structures. That may be true in many cases, but if there is an incipient failure due, for instance, to uncontrolled seepage, piping and erosion, the characteristic dimension of that feature will be much smaller and it is possible, even likely, that high frequency motions can impact the potentially unstable local structure and trigger a larger progressive failure. This phenomenon is illustrated with a simple example. The importance of correctly modeling progressive failure is also addressed.

In current practice, vertical ground motions are often ignored in design of concrete gravity dams as they are considered not to effect on the performance of the dams. In this study, a seismic assessment is completed by modelling a typical concrete gravity dam located in a seismically active region using finite element analysis software PLAXIS 3D. This was done to see if varying the seismic parameters affects the overall performance of the dam, and whether the vertical peak ground accelerations influence the design process. The model dam is exposed to a variation in seismic parameters to analyze its response using PLAXIS 3D’s pseudo static analysis function. The dam’s performance against two failures was assessed: global factor of safety and maximum vertical deformation. This analysis is based on six seismic load combinations (100 % horizontal with 0 % vertical, 100 % horizontal with 30 % vertical, 100 % horizontal with 67 % vertical, and vice versa of these combinations) of horizontal and vertical peak ground accelerations. Results show that although variation in the vertical component does not have a critical effect on the global factor of safety of the dam, it affects the vertical deformation under the dam. When 100% vertical PGAs are applied, they result in 56mm deformation compared to 49mm when they are ignored, 52mm when reduced to 30%, and 54mm when reduced to 67%. Varying the horizontal PGAs was seen to have negligible effect on the vertical deformations, however horizontal PGAs were found to be critical in design for the global factor of safety. When 100% horizontal PGAs were applied, the factor of safety dropped to its lowest value of approximately 2.0 in all three cases despite an increase in vertical PGAs. This illustrates that the vertical component of an earthquake affects the design against settlements under the dam, if not the slope stability failures, and hence cannot be ignored in the overall seismic design process.

Recently, seismic diagnosis and reinforcement design for railway embankments have been conducted in Japan. In the seismic diagnosis for the existing embankments, it is general to adopt the saturated strength characteristics of embankment materials evaluated from triaxial compression tests using specimens sampled at representative points. This evaluation method for their strength characteristics corresponds to the assumption that the density of the embankment is uniform and that the entire area is saturated. The seismic resistance of the embankment may be underestimated compared to its actual resistance, and the quantity of reinforcement required to ensure seismic stability and the construction costs increase. This paper examined the estimation method for the density distribution of embankment from shear wave velocities. In this method, the density is estimated from the shear wave velocity obtained by surface wave exploration, referring to the results of bender element tests with different densities of specimens. The estimated results were generally consistent with the densities measured in the field, suggesting that it may be possible to estimate the density distribution of the existing embankment. The seismic diagnosis for railway embankments was conducted considering their dry density distribution evaluated by the proposed method, and the results were compared with those of the conventional method to confirm the increase in the factor of safety during an earthquake.