Site-specific ground response analysis and liquefaction assessment of Vijayawada city (India)

Safety against earthquake hazards can be achieved by considering site safety against geotechnical problems and structural safety against dynamic forces. Geotechnical problems such as amplification, landsliding and soil liquefaction are dangerous in regard to the scale of damage. Assessment of risk against such problems is a part of seismic microzonation process. Seismic risk is highly affected by risk factors due to geological environment and geotechnical properties of soils. In this study, it is attempted to identify and develop hazard maps against seismic hazard for Vijayawada city, India, where the subsoil consists of thick alluvial formations along the river. In particular, the study aims at the evaluation of site effects using the available geotechnical data and carrying out microtremor testing in the study area. The geotechnical zonation of the subsoil of the city suggests a high vulnerability of the physical environment in addition to site amplification of the ground motion phenomena. The ground response analysis at the surface was conducted by 1D equivalent linear method and by microtremor testing. From the ground response analysis, peak acceleration, frequency and amplification parameters were assessed and the city was divided into different zones corresponding to each value. Liquefaction hazard was quantified using SPT-based method in combination with the dynamic analysis. These findings supply an indispensible tool for the seismic retrofitting of the buildings and for the mitigation of the seismic risk for small to medium earthquakes in the city.