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The MS6.2 earthquake occurred in Jishishan, Gansu Province, China, on December 18, 2023. Based on some strong seismic acceleration time histories captured by some stations of China National Strong Earthquake Observation Network and National Earthquake Early Warning Network, the spatial distribution characteristics, rupture directivity effect, hanging wall and footwall effect, response spectrum characteristics, and attenuation of the peak ground acceleration (PGA) were analyzed in this paper. It can be used as reference for the site determination of post-earthquake reconstruction and seismic design of engineering structures. The analysis shows that the spatial distribution of strong ground motion of the Jishishan MS6.2 earthquake is mainly controlled by the distribution of causative fault. Near the fault, the effect of rupture directivity is obvious. The effect of hanging wall and footwall significantly affects the distribution of PGAs for this earthquake, causing a pronounced asymmetric pattern about PGAs relative to the fault, with slower attenuation on the hanging wall compared to the footwall. The type of site obviously affects the characteristics of response spectrum. The ground motion intensity observed at the epicenter of this earthquake significantly exceeded the levels of rare and extremely rare seismic events in the current seismic design codes. The attenuation relationship of PGA obtained by regression analysis shows that ones in the 5th generation Chinese ground motion parameter zoning map for the Qinghai-Tibet region underestimate the horizontal PGA.

As the Nairobi–Malaba Railway traverses the East African Rift Valley, it has complex engineering geological conditions due to the development of its geological formations. Since March 2018, four large ground fissures have occurred in the East African Rift Valley area crossed by the Nairobi–Malaba Railway engineering construction, posing a significant threat to the safety of the railway engineering. According to the field investigation, it is initially considered that the ground fissures are caused by the loss of strength of the lower soil layers. In view of the fact that the settlement occurred during the rainy season and no earthquake events were recorded in the local and nearby areas during that period, it is inferred that the ground fissures originated from the subduction of the underlying soil layer by the submerged erosion of groundwater. For this reason, a further field investigation was conducted and a geological trench was directly excavated to the underlying rock for the uneven ground settlement, which revealed that the overlying soil layers are mainly silty clay layers and volcanic ash layers, and there are some deep and long cracks of a certain width on the underlying volcanic rock layer and there is gas flow spilling from the cracks. The field investigation also found the existence of some penetrating holes in the volcanic rock layer and caves beneath the volcanic rock layer. Based on the field investigation and phenomenological analysis, it is concluded that during the rainy season, the alternating action phenomenon of downward seepage of water in the surface soil layer and upward reflux of water beneath the volcanic rock layer happened through the cracks and penetrating holes on the volcanic rock layer, and the alternating effect of groundwater flow causes some silty clay and volcanic ash particles to flow into the caves and cracks beneath the volcanic rock layer, which leads to the generation of ground fissures. In addition, to further confirm the reliability of this interpretation of the generative mechanism of ground fissures, related results of conventional geotechnical tests on the overlying soil were studied, which verified the conclusion obtained. [ABSTRACT FROM AUTHOR]

Microtremor tests and finite element numerical simulations were used to analyze the seismic ground motion effects of the Yunnan Dayao sedimentary basin. The results of the microtremor relative to the reference point spectral ratio (HS/HR) method showed that the spectral ratio curves of each observation point in Dayao basin show multipeak characteristics, indicating that the site consists of different soil layers; the predominant frequencies of each observation point mainly are 6~9 Hz in the basin and there are lots of differences in the predominant frequencies of different observation points, which indicate that the site stiffness of each observation point is different; the differences of spectral ratios between the east–west directions (EW) and the north–south directions (NS) reveal the site's anisotropy. The amplification coefficient characteristics of each observation point in the basin obtained by numerical simulation show that the predominant frequency is 6 ~ 9 Hz; the amplification coefficients of each observation point are different; the edge effect and the focusing effect amplify the seismic ground motion in the basin; the different amplification coefficients of the two sub‐basins reflect the significant effect of the basin soil layers' differences on the seismic ground motion, the site is softer and amplification coefficients are larger; the slope degree of basin edges significantly affects the seismic ground motion near the basins edge, the amplification coefficients of the slope steeper and amplification coefficients larger. This study demonstrates that the microtremor test spectral ratio (HS/HR) method has good reliability applied to the analysis of basin effect and combining the finite element numerical simulation method is more effective in revealing the basin effect mechanism. [ABSTRACT FROM AUTHOR]

In this paper, a multi-transmitting formula (MTF) was integrated into ANSYS software through secondary development, enabling dynamic finite element simulation of wave propagation in infinite domains. The numerical reliability and accuracy of the MTF were verified through a plane wave problem involving a homogeneous elastic half-space, as well as 3D scattering and source problems in a three-layered soil site. Additionally, a comparative analysis of various artificial boundaries was conducted to highlight the advantages of the MTF. Field observations of environmental vibrations caused by high-speed railway operations revealed localized amplification of vibrations along the depth direction at the Kunshan segment of the Beijing–Shanghai high-speed railway. Based on these observations, a series of numerical analyses were conducted using the customized ANSYS integrated with the MTF to investigate the underlying causes and mechanisms of this phenomenon, as well as the spatial variation characteristics of foundation vibrations induced by bridge vibrations during high-speed train operations. This study reveals the mechanism by which the combined effect of bridge piles and soft soil layers influences the depth variation in peak ground accelerations during site vibrations. It also demonstrates that the presence of bridge piers and pile foundations effectively reduces vibration intensity in the vicinity of the railway, playing a crucial role in mitigating vibrations induced by high-speed train operations. [ABSTRACT FROM AUTHOR]

The study of dynamic responses and operational safety of high-speed trains under seismic excitation has increasingly relied on numerical simulation as the most effective and convenient research approach. The majority of studies only focus on single-car formation, and fewer utilize train models with actual standard formation, inevitably resulting in differences in dynamic characteristics of train models and simulation results. Furthermore, trains also have different standard formations in different countries and operating scenarios. Therefore, the influences of train formation on the dynamic responses and operational safety of trains under seismic action are investigated. Hence, a detailed train/vehicle–track coupled dynamics model was established to simulate trains under non-uniform seismic ground motion. Moreover, due to wheel–rail contact simulation being the key factor constraining simulation efficiency, based on the influence pattern of train formation, whether fewer train formations can achieve the same simulation accuracy as the 8-car standard formation is also explored in this paper considering seismic wave propagation effect. Results indicate that variation in train formation can influence the dynamic responses of a coupled system significantly from both the perspective of wheel–rail interaction and vehicle kinematic responses. Moreover, the 5-car formation model can better meet the accuracy requirement and significantly improve computational efficiency compared to 8-car formation model. [ABSTRACT FROM AUTHOR]

Urban expressways take on rapid and external transport in the city due to their fast, safe, and large capacity. Implementing intelligent and active traffic control can effectively improve the performance of urban traffic and mitigate the urban traffic congestion problem. Real-time traffic guidance is one critical way of intelligent active traffic control, and travel time is the most important input for real-time traffic guidance. We employed and improved a machine learning method called the evolving fuzzy participatory learning (ePL) model to predict the freeway travel time online in this paper. The ePL model has a promising nonlinear mapping potential, which is well suitable for the traffic prediction. We used generalized recursive least square (GRLS) to improve the estimation accuracy of the model's parameters. This model is a fuzzy control model. Its output is the forecasting result which is also the fuzzy reasoning result. We tested this model by comparing it to other travel time prediction approaches, with the freeway data from the Caltrans Performance Measurement System. The results from the improved ePL model showed mean absolute error of 5.941 seconds, mean absolute percentage error of 1.316%, and root mean square error of 10.923s. The performances are better than those of the baseline models including ARIMA and BPN. This model can be used to predict the travel time in the field to be used for active traffic control and traffic guidance., Author(s): Yongyi Li (corresponding author) [1]; Ming Zhang [1]; Yixing Ding [2]; Zhenghua Zhou [3]; Lingyu Xu [1] 1. Introduction The ways to predict travel time have undergone a significant [...]

This paper obtained a semianalytical solution for the P-wave scattering problem by an arbitrary-shaped canyon in a saturated half-space by using Biot's theory, the wave function expansion method, and the moments method. Firstly, based on the Biot fluid-saturated porous media theory and the wave function expansion method, the wave potentials which automatically satisfy the zero-stress boundary condition on the surface of the half-space are obtained. Then, the boundary value problem is transformed into an algebraic problem by the method of moments according to the boundary conditions, and then solved numerically by truncation. By adjusting the parameters, the saturated medium in the original model approximately degenerates into a single-phase elastic medium, and the correctness of the proposed method is verified by comparing it with published results. Finally, the effects of the canyon shape, the porosity of the soil, and the incidence angle and frequency of the incident wave on the amplitude of ground surface motion are investigated. The results show that the incidence angle has a significant effect on the ground surface motion, while the porosity of the soil has little influence on the amplitude of surface motion. The influence of canyon shape on surface motion is mainly reflected in the shielding effect on the incident wave. Although P-wave scattering by a canyon is a traditional problem, most of the analytical solutions are limited to solving the scattering of seismic waves in geometric regular canyons. However, the actual shape of the canyon is not regular, which limits the application of closed analytical solutions in practical engineering. In this paper, the scattering of P-waves in arbitrary-shaped canyons is successfully solved by using a semianalytical method combined with a numerical method-moments method, which provides a possibility for engineering application. [ABSTRACT FROM AUTHOR]