Shear wave velocity estimation of the near-surface materials of Chittagong City, Bangladesh for seismic site characterization

The average shear wave velocity of the near-surface materials down to a depth of 30 m (V-s(30)) is essential for seismic site characterization to estimate the local amplification factor of the seismic waves during an earthquake. Chittagong City is one of the highest risk cities of Bangladesh for its seismic vulnerability. In the present study, the V-s(30) is estimated for Chittagong City using the multichannel analysis of surface waves (MASW), small scale microtremor measurement (SSMM), downhole seismic (DS), and correlation between the shear wave velocity (V-s) and standard penetration test blow count (SPT-N). The V-s(30) of the near-surface materials of the city varies from 123 m/s to 420 m/s. A VI map is prepared from the V-s(30) of each 30 m grid using the relationship between the Holocene soil thickness and the V-s(30). Based on the V-s(30), the near-surface materials of Chittagong City are classified as site classes C, D, and E according to the National Earthquake Hazards Reduction Program (NEHRP), USA and as site classes B, C, and D according to the Eurocode 8. The V-s(30) map can be used for seismic microzonation, future planning, and development of the city to improve the earthquake resiliency of the city. (C) 2016 Elsevier B.V. All rights reserved.