To ensure the seismic safety of important buildings and infrastructure facilities in seismically active areas, it is necessary that, in addition to the various ground motion parameters, the seismic hazard is also characterized in terms of many other destructive natural effects of earthquakes like soil liquefaction and permanent fault displacement for example. The probabilistic seismic hazard analysis methodology can in principle be applied to quantify any of the destructive effects of the earthquakes in a region, provided a formulation has been developed to compute the probability with which a specified level of that effect can be exceeded at a site of interest due to given earthquake magnitude and location. Several investigators have developed necessary relationships and methodologies to estimate this probability for the permanent fault displacement, which may be a potential and primary cause of damage to long structures like bridges, tunnels, pipelines, dams and buried structures, if an active fault happens to cross or pass by such a structure. Based on a comprehensive literature survey and critical analysis of the results obtained for various possible alternatives, we have finalized a methodology for probabilistic fault displacement hazard analysis suitable for a 257 km long strand of the main boundary thrust (MBT) in the Garhwal-Kumaon Himalaya. Formulations are proposed for estimation of both the on-fault principal displacement and the off-fault distributed displacement, which can also be applied to any other thrust fault in any other segment of the Himalaya. The application of the proposed methodology to obtain the on-fault displacement estimates for a site at the midpoint of the selected strand of the MBT is found to provide physically realistic displacement values for very long return periods of upto 100,000 years. The off-fault displacements are found to decrease very fast with distance from the site on MBT and become practically insignificant at a distance of only two km.

When traversing through an active strike-slip fault, buried pipelines may be subjected to permanent ground deformation (PGD), causing large strains in the pipeline during an earthquake. The presence of bends near the fault-crossing zones may further increase the strain in the pipe. Moreover, it is well acknowledged that bends are the most vulnerable location to earthquake damage, mainly when compressive strain develops due to PGD. Hence, most design guidelines recommend constructing pipelines without field bends, elbows, and flanges crossing the fault zone. However, it is not always possible to provide only a straight segment of the pipeline, especially for blind faults where the location of the faults is unknown. Hence, the present study aims to investigate the response of buried continuous steel pipelines with field bends subjected to strike-slip faulting by conducting an extensive parametric study. A three-dimensional pipe-soil interaction model is developed in a finite element framework for this study. The pipeline response in terms of its maximum von-Mises stress and maximum longitudinal stress and strain due to fault crossing is studied for various influencing parameters such as pipe bend angle, soil strength, pipe burial depth, and distance of the fault trace from the bend. Based on the results obtained, suitable relationships in terms of modification factors over the response of a straight pipeline as a function of a few critical parameters are determined using regression analyses. It is concluded that providing bends to the pipeline can significantly affect its structural response when subjected to fault displacement when the fault trace is close to the pipe bend. The primary outcome of this investigation would be to suggest a simplified methodology to estimate the response of pipelines having field bends while crossing fault lines from the response of straight pipelines in a similar scenario.

Large-scale loss of life and property occurred in Kahramanmaras and its districts, which are the city center where the epicenters of the earthquake couples that occurred on February 6, 2023, in Turkiye. Major damage has occurred in different structural systems due to the earthquake. In addition, fault traces that are the source of the earthquake were clearly observed on the ground surface. In this study, the effects of both earthquakes on soil, reinforced concrete, masonry, prefabricated, and other structural systems were evaluated observationally in Kahramanmaras and its districts. Comparisons were made on the last two earthquake maps used in Turkiye for the locations of strong ground motion measuring devices in Kahramanmaras. The masonry structures, which are common in rural areas in the epicenter, have been heavily damaged because they have not received engineering service. However, it is seen that the concrete buildings have insufficient strength and ductility. A similar situation is also present in industrial precast structures, and it has been observed that the damaged and collapsed in these structures are manufactured without complying with the type connection details given for prefabricated reinforced concrete structures in the codes. It has also been observed that the soil-structure interaction is the most determining parameter in the structure's performance in these earthquake couples. Especially in weak soils, the damage to the structures has been quite heavy. The field data obtained from the earthquakes showed that some of the conditions of the current earthquake code should be discussed again.