Local site conditions recognized as a determining factor in assessing the extent of seismic hazard and damage distribution during earthquakes. Present study emphasizes seismic hazard of international business corridor of Agartala town capital of Tripura, one of the northeastern state of India categorized as highest seismic zone (zone V) attributing seismic response of local subsoil deposits under site-specific scenario earthquake motions including liquefaction susceptibility prediction. One-dimensional nonlinear ground response analysis with input of geotechnical parameters was carried using DEEPSOIL (2018) program across central zone of Agartala city and liquefaction susceptibility analysis are performed based on standard penetration test (SPT) utilizing well-established empirical relationship. The novelty of results lies in use of site-specific dynamic parameters of subsoil and synthetic ground motions based on scenario earthquake. Besides, numerical model was validated with a recent past liquefaction case study in Tripura which also attributes key highlight of this study. Key seismic hazard parameters in the form of peak ground acceleration (PGA), amplification factor (Af), and predominant frequencies (fn) are presented through geographical information based spatial maps. These maps provide crucial inputs for planners and designers for future urban planning along with seismic strengthening of existing infrastructures. This comprehensive approach offers new perspectives on seismic hazard assessment and future management plan in this region.

Near-fault impulse earthquakes induce complex dynamic responses in bridge structures, potentially resulting in significant structural damage. On May 22, 2021, a magnitude 7.4 earthquake struck MaDuo County in the Guoluo Autonomous Prefecture of Qinghai Province, with the Yematan Bridge sustaining the most extensive damage during this seismic event. This study employs synthetic near-fault impulsive ground motions and the LS-DYNA explicit dynamic analysis software to investigate the mechanisms underlying the observed seismic damage and the subsequent failure of girders. The simulations effectively replicated the collisions involving the main girder, the damage to the shear keys, and the falling girders. Furthermore, post-earthquake soil exploration data, analyzed using DEEPSOIL site analysis software, are integrated to assess the amplification effects of ground vibrations at the bridge site. The analysis revealed that the longitudinal peak ground acceleration (PGA) experienced by the Yematan Bridge is approximately 6.8m/s(2), while the transverse PGA is about 4.2m/s(2). The damage to the bridge occurred in two distinct stages: initially involving collisions between the shear keys and the main girder, followed by a domino effect, leading to the failure of multiple girders. The primary factors contributing to the structural damage included impulsive seismic forces, short pier heights, transient bearing failures, and substantial longitudinal and transverse displacements of the main girder due to ground vibrations and inertial effects, which ultimately resulted in shear key damage and the subsequent collapse of girders. Despite the Yematan Bridge being designed to withstand seismic intensity rated at VIII, DEEPSOIL's inversion analysis indicated a bedrock PGA of 4.26m/s(2) and a corresponding seismic intensity of IX. At the same time, the earthquake-resistant rating for MaDuo County is designated as VIII. This discrepancy in seismic intensity zones significantly exacerbated the severity of the girder failures. The numerical findings and conclusions presented in this study provide critical insights for the seismic design of simply supported highway bridges located in near-fault regions.

An earthquake is a natural occurrence that has the potential to trigger liquefaction. In fine sandy soil layers with a shallow water table, earthquakes can cause a rapid increase in excess pore water pressure (PWP), compromising the soil's effective strength and increasing the risk of liquefaction. According to the Indonesian Liquefaction Vulnerability Zone, North Sumatra is categorized as a liquefaction area. Langkat is one of the regencies in North Sumatra that is categorized as having a moderate liquefaction vulnerability. Therefore, Langkat was chosen as a research area to investigate liquefaction potential using pore water pressure (PWP) with empirical methods by Yegian and Vitelli (1981) and numerically using Deepsoil V7.0. The study area consists mostly of sand with shallow groundwater levels due to its proximity to rivers and high seismic zones associated with the Sumatran fault. The analysis is based on Standard Penetration Test data and laboratory tests from 2 boreholes with a depth of 30 m. The lts show that full liquefaction potential exists at BH 01, a depth of 9-11 m below the ground surface with r(u) > 0.8 and a limit of gamma(max) >= gamma. Marginal liquefaction occurs at BH 02 at a depth of 3.5 m with r(u) > 0.8 and gamma(max) < gamma(limit). Evaluation of the excess pore water pressure ratio in area prone to liquefaction is important because this condition can cause rapid damage. The low bearing capacity of the building foundation is proven by the r(u) value approaching 0.8.