SIMPLIFIED ENGINEERING GEOMORPHIC UNIT BASED SITE CHARACTERIZATION OF DHAKA CITY DAP AREA

The intensity of ground motion mainly depends on the source, source-to-site distance, and local site condition. Depending on the local geology of the site, the seismic ground motion could be amplified or de-amplified to reach the surface. To accurately measure the acceleration of surface ground motion, site response analysis is mostly used. In this study, one-dimensional nonlinear site response analysis is performed based on the prepared engineering geomorphic unit map of the Dhaka DAP area. The engineering geomorphic unit-based map was prepared from image analysis and verified with the boreholes data. 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. Moreover, two synthetic time histories are generated and used for the site response analysis. We observed that, for the selected earthquake ground motions, the near-surface soil response of the DAP area shows de-amplification of acceleration in the short period and amplified acceleration in the long period. 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.