Simplified Engineering Geomorphic Unit-based Seismic Site Characterization of Detailed Area Plan of Dhaka City

Strong ground motion can amplify and prolong due to local site conditions; consequently, it can cause severe damage in poor non-engineered structures. Usually, site response analysis is used to predict strong motion characteristics at the surface. In this study, one-dimensional nonlinear site response analysis is performed based on the prepared simplified engineering geomorphic unit of the Detailed Area Plan (DAP) of Dhaka City. The engineering geomorphic unit-based map was prepared from image analysis and verified with the collected boreholes data and surface geology map. For response analysis, the earthquake time histories are selected from the PEER NGA WEST2 data set, and BNBC 2020 uniform hazard spectrum (UHS) is considered as the target spectrum. In addition, two synthetic time histories are also generated and used for the site response analysis. For the selected earthquake ground motions, the near-surface soil response of the DAP of the Dhaka City area shows de-amplification of acceleration in the short period and amplified acceleration in the long period. The amplified long-period acceleration can cause severe damage in non-engineered long-period structures. The outcome of this study can be used to prepare a seismic risk-sensitive land use plan for the future development of the DAP area of Dhaka City.