Nepal, a landlocked country in the Himalayan region, was struck by a devastating earthquake of magnitude Mw 7.8 on 25th April, 2015. The major earthquake destroyed millions of structures and caused immense loss of life. Unfortunately, only a few seismic stations recorded the earthquake, presenting a challenge for understanding the observed non-uniform structural damage in the region. In this study, synthetic ground motions are generated at the bedrock level using the stochastic finite fault method. The ground motions are later estimated at the surface level using the equivalent linear site response analysis program, using soil profiles from 9 borehole locations from the Kathmandu basin. The key characteristics of the synthetic strong ground motions are tabulated and analyzed. Peak ground accelerations (PGA) at bedrock in the region range from 0.064 g to 0.09 g. Remarkably, the Kankali site (BH6) exhibits the highest outcrop acceleration response, with bedrock and outcrop PGAs measuring 0.083 g and 0.170 g, respectively. Observations indicate that soil profiles experience their greatest amplification ratio within the frequency range of 1.2 Hz-7.3 Hz. Plots of response spectra for the synthetic ground motions are derived and compared with the provisions of the Nepal's seismic design code. The key characteristics of strong ground motions and observations from the derived response spectra correlate well with the available reports of structural damage in the earthquake. These observations provide valuable insights into seismic vulnerability and soil behavior that is crucial for seismic hazard assessment and engineering design considerations.

Kathmandu Valley, the capital of Nepal, is located in the seismically active Himalayan belt and has a history of devastating earthquakes causing substantial loss of life and property damage. This study employs Probabilistic Seismic Hazard Analysis (PSHA) using the Foulser-Piggott Attenuation (FPA) model and Travasarou et al. (2003) with R-CRISIS software to calculate Arias intensity in Kathmandu Valley. Historical and recent seismic data within a 500-km radius were analysed, and the earthquake catalogue was declustered and standardized using ZMAP software, a tool developed for the statistical analysis and visualization of earthquake catalogues. Additionally, a Digital Elevation Model (DEM) based topographic analysis was conducted to assess the impact of local topography on seismic site response providing insights into, slope, soil amplification factors, and shear wave velocity across the region. The results reveal Arias intensity values ranging from 0.225 to 0.241 m/s at 2% and 10% probability of exceedance corresponding to 475 and 2475 years, mapped using ArcGIS. The analysis revealed that southwestern Kathmandu and Lalitpur exhibit higher Arias intensity values, while intensity decreases gradually from southwest to northeast. The DEM analysis further revealed that areas with low slopes, particularly in central Kathmandu, have higher soil amplification factors, potentially amplifying seismic waves. The shear wave velocity distribution highlights lower values in sedimentary deposits, indicating increased seismic vulnerability. These findings emphasize the need for effective urban planning and disaster preparedness strategies to mitigate earthquake impacts in Kathmandu Valley.

Erzurum province is located close to two important faults, namely the North Anatolian Fault Zone and the East Anatolian Fault Zone. Additionally, numerous local faults such as the A & scedil;kale, Ba & scedil;k & ouml;y-Kandilli, Erzurum-Dumlu, Paland & ouml;ken, and Horasan-Narman Fault Zones could potentially trigger devastating earthquakes for Erzurum province. All these seismic hazard sources require a well-understanding of the soil dynamic properties in Erzurum province. The single-station microtremor method were carried out at 45 points to determine the Atat & uuml;rk University Central Campus-Erzurum soil dynamic parameters with this motivation. Seismic vulnerability index and seismic bedrock depth values were calculated with the help of empirical relations using the soil dominant frequency and soil amplification factor values calculated from the horizontal/ vertical spectral ratio method. The south-eastern region of the study area exhibits characteristics such as low soil dominant frequency values, high soil amplification factor values, elevated Kg values, and considerable engineering bedrock depth. This area is particularly vulnerable to potential earthquake damage due to its high sediment thickness and susceptibility to site effects. Notably, points three and four also demonstrate low soil dominant frequency values, coinciding with the locations of hospitals and administrative units. Therefore, it is imperative to intensify site effect investigations, especially using active sources of geophysical methods in these specific areas.

The accumulated water within the drainage layer of a final cover system of municipal solid waste (MSW) landfills is the foremost reason for the failure of final covers. This study adopts a pseudodynamic (PD) method to assess the seismic stability of landfill cover systems against direct sliding failure (DSF) and uplifted floating failure (UFF). The novelty of this study lies in consideration of the simultaneous action of hydrostatic, hydrodynamic, and seismic forces on the cover soil layer. The factors of safety (FS) against DSF (FSds) and UFF (FSuf) failures are evaluated by incorporating the effects of shear and primary (P) wave velocities, the phase difference between the seismic waves, soil amplification, time duration, and frequency of the earthquake. The influence of phase change on FSds and FSuf is examined, and the results are compared with those obtained by the pseudostatic (PS) method. The results show that the PD method yields a 29.11% increase in FSds and a 23.29% reduction in FSuf values compared with the PS method. The effects of horizontal seismic acceleration coefficient, slope angle, stability number, cover soil layer thickness, and height of landfill on FSds and FSuf are observed for different conditions of immersion ratio (Ir). Consideration of the soil amplification factor reduces the values of FSds and FSuf by 12.48% and 18.46%, respectively. The cover soil thickness (h) should be chosen between 0.047H and 0.067H, where the height of the landfill is H, to maintain safety against DSF and UFF modes for Ir = 0.3. Further, design charts are presented to compute the optimum thickness of the cover soil under earthquake loading conditions by targeting FSds and FSuf >= 1.15. Pseudodynamic (PD) stability analysis of veneer cover systems with accumulated water in the drainage layers is useful to model the behavior of landfill covers when subjected to various external loading conditions, which include earthquakes, heavy rain, and other environmental factors. The results of the analysis could be used to optimize the design of landfill covers to ensure their stability over time. The analysis could help engineers determine the appropriate thickness of the clogged drainage layer and other design parameters that ensure the long-term stability of the landfill cover. It could help assess the risks associated with earthquake loading or heavy rain and determine the probability of failure of the landfill cover system. These results could be used to plan and implement risk mitigation measures to reduce the potential for damage or environmental harm. In addition, it could be used to monitor the performance of landfill covers against direct sliding failure (DSF) and uplifted floating failure (UFF). This study proposed design charts that could facilitate practicing engineers to achieve safe, cost-effective, and reliable design of final covers of municipal solid waste (MSW) landfills. The findings of this study could be beneficial when standardizing the international design codes for the seismic stability of veneer cover systems.