Seismic Microzonation and Probability of Ground Failure Assessment Caused by liquefaction for Bogura District, Bangladesh

The aim of this study is to create a Mercalli intensity map and evaluate the ground failure probability caused by liquefaction in the Bogura district. To generate a Mercalli intensity seismic microzonation map, first the shear wave velocity (Vs) was determined by analyzing data from 345 soil test reports. The conversion of Vs to site amplification factor (AF) and Peak Ground Acceleration (PGA) was carried out using the widely used empirical equations, considering earthquake magnitudes 1850–2023. Finally, the susceptibility of liquefaction was evaluated for the study area using 345 borehole data, considering a probable earthquake magnitude and site-specific PGA. Some of the frequently used empirical methods are utilized for the evaluation, and the results are presented in the form of hazard maps indicating factors of safety, liquefaction potential, and ground failure probability. The results demonstrate that the least and maximum PGA are both 0.06 g and 0.16 g, while the AF ranges from 1.903 to 3.98 between the minimum and maximum. Moreover, the surface acceleration (SA) varies between 0.143 g and 0.51 g. Based on the Mercalli Intensity seismic microzonation map, 22.45% of the areas have intensity VII, 72.9% of the regions have intensity VIII, and 4.65% of the areas have intensity IX. The hazard map reveals that 2% of the study region is judged to be at extremely high risk for ground failure due to liquefaction during the scenario earthquake. Additionally, it was determined that 13% and 44% of the study region's regions were at high or moderate risk of ground failure under the aforementioned earthquake scenario. The intensity and hazard maps created for Bogura district are crucial to achieving sustainable development goals.