Bihar, an Indian state located in seismic zones III, IV, and V, has experienced severe earthquakes in the past. Due to the presence of alluvium soil deposits over the bedrock in the Bihar region, seismic waves near the ground surface can amplify and cause catastrophic damage to existing structures. Therefore, to ensure the safety of the structures, it is imperative to assess the amplification level of seismic waves near the surface. This study presents a new empirical correlation for the site classes C, D, and E of the Bihar region, which estimates the spectral acceleration (Sa) at the required time period. These site classes of the Bihar region refer to the classification of soil and geological conditions based on their behaviour during seismic events, specifically their impact on seismic wave amplification, ground shaking, and overall earthquake hazard, as per NEHRP classification. The results of this investigation can be applied to enhance the seismic design of structures and, hence, mitigate the seismic risk. Moreover, the developed empirical correlation for Sa can be used to estimate the design spectrum acceleration at the surface level for site classes C, D, and E of the Bihar region.

This study uses a fully coupled dynamic effective stress analysis method to evaluate the seismic response of a site containing silty sand which is a liquefiable interlayer. A generalized plasticity model is employed to describe the liquefaction behavior of silty sand under seismic action, and a nonlinear constitutive model is used to account for the nonlinear and hysteretic characteristics of non-liquefiable soils. The parameters of constitutive model were calibrated from the shear wave velocity and results of resonant column tests on different soils in a borehole. The results indicated that (1) A new spike with a period of approximately 1 s was observed at the top of the liquefiable interlayer compared to that at the bottom of the interlayer, reflecting a common seismic response characteristic induced by the rise in the excess pore water pressure (EPWP); (2) The low-frequency input motion caused higher EPWP within the liquefiable interlayer and more ground settlement at the consolidation stage; (3) The increase in either peak horizontal acceleration or peak vertical acceleration of input motions resulted in higher increase in the EPWP and ground surface settlement. Moreover, the vertical seismic component in near-field earthquakes has much more significant effect on the ground settlement in liquefiable sites than that in far-field earthquakes.

This study analyzes the Pazarcik and Elbistan earthquakes, which occurred on February 6, 2023 and are among the most destructive seismic events of the 21st century. Since the greatest damage was seen in Hatay in these earthquakes centered in Kahramanmaras, the study aims to contribute to the field of earthquake engineering by evaluating the seismic data obtained from these regions. In the first part of the analysis, peak ground accelerations (PGA) recorded at the stations in Kahramanmaras and Hatay were examined and these data were compared with the DD1 (maximum considered earthquake) and DD2 (design basis earthquake) design levels of the Turkish Building Earthquake Code (TBEC 2018). In addition, the effects of ground properties and proximity of faults on seismic records obtained from various stations were evaluated by examining the PGA distribution spatially. The impacts of factors such as the near-fault effect, directivity effect, ground amplification effect and impulse-like motions were determined by examining the peak ground accelations, peak ground velocities, peak ground displacements and spectral accelerations. The study uses NGA-West2 Ground Motion Prediction Equations (GMPEs) to evaluate peak ground accelerations in stiff soil and to consider impulse and directivity effects. In addition, the applicability of USGS Vs30 maps in Turkiye is evaluated by comparing with AFAD data. These comprehensive analysis provide critical insights from a structural safety perspective on how seismic characteristics change with ground properties and proximity to earthquake sources.