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Abstract:
Sylhet, the 4th largest city of Bangladesh, is located in the north-eastern Division of Sylhet with the highest seismic zone coefficient (Z=0.36) of the recently updated Bangladesh National Building Code (BNBC-2020). Major faults capable of generating large magnitude (M≥7) earthquakes are located within and in the vicinity of the Sylhet Division. Most prominent historical earthquake is the 1918 Magnitude 7.6 Sri Mangal Earthquake with epicenter near Sri Mangal, a town about 75 km south of Sylhet city. The east-west trending Dauki fault along the northern Bangladesh-India border and much closer to the Sylhet city, is also considered as a potential seismic source. A brief review of the research work done related to seismic sources and seismic hazard assessment for Sylhet city is presented. Critical review of published probabilistic and deterministic seismic hazard assessment studies have been performed. More recently, the effect of a large magnitude earthquake on the Dauki fault on the seismic input motion for the city of Sylhet is studied using an advanced version of the Neo-Deterministic Seismic Hazard Assessment (NDSHA) software based on higher frequency computations developed at University of Trieste, Italy. Estimated ground motions from various seismic hazard assessment studies are compared with code provisions of BNBC-2020 and neighbouring Indian building code. Differences exist and the implications of such differences will be addressed. It is concluded that the estimated ground motion may exceed code specified values and more source specific studies need to be carried out for this region.
