BNUS Starts Research Work on Seismic Microzonation for Cox’s Bazar Municipality
Bangladesh is located in a tectonically active zone. Cox’s Bazar, situated in the southeastern part of the country, is a strategically and economically important area. The district is exposed to most devastating natural disasters of the country where earthquake has recently appeared as additional threat. In the seismic zoning map of Bangladesh, provided in BNBC (Bangladesh National Building Code 1993), Cox’s Bazar has been shown under Zone II with design peak ground acceleration (PGA) value of 0.15g (Z=0.15). This level of acceleration may be considered as more or less equivalent to a seismic intensity of VIII. Historical information reveals that earthquakes of magnitude between 6 and 7 have occurred around the city in the past. Thus Cox’s Bazar and the nearby area are considered to fall in the High Risk Zone for earthquakes. The frequent earthquakes in and around the country, particularly Chittagong and Cox’s Bazar regions, also point toward the potential of such intensity earthquakes, even much higher.
Cox's Bazar, having been a great tourist resort a rapid urbanization has occurred in the last few decades including various establishments, construction of significant number of buildings and other structures in an unregulated manner and without seismic design considerations. The consequences of moderate to strong earthquake event can be catastrophic if such a densely populated urban area is affected.
One of the major concerns during an earthquake is the presence of vulnerable soils near the ground surface. In order to assess seismic vulnerability based on Ground Susceptibility, Seismic Micro Zonation is considered to be the first step towards a seismic risk analysis and mitigation strategy for urban areas. Liquefaction phenomena can affect buildings, bridges, buried pipelines, lifelines and other constructed facilities in many different ways. Local soil effects can amplify the ground motion and thus lead to intensity greater than the projected ones in certain areas causing more damage. Landslide has become very common in the hilly areas of southeastern Bangladesh, especially in Bandarban, Rangamati, Khagrachhari and Cox's Bazar. Every year especially in the rainy season landslides take place in both natural and man-induced slopes. Considerable number of buildings, roads and other infrastructures are damaged and valuable lives are lost in these incidents. The loss of lives and properties due to Landslide events in Cox’s Bazar is also very significant.
No such research has been conducted so far for determining the Ground Susceptibility combining liquefaction potential, site amplification and landslide potential at a time and finally developing Hazard Zonation maps for Cox’s Bazar Municipality. To perform this research field survey has been conducted at entire area under Cox’s Bazar Municipality and locations to be investigated have been identified preliminary. Sub-soil data of the area has been collected from different sources. Twelve more subsoil investigations are going to be carried out soon for this research. Hilly regions of the area have been surveyed and samples have been collected for laboratory investigations. Accumulating the results of the investigations liquefaction, site amplification and landslide potential maps for Cox’s Bazar will be developed. These Zonation maps will add value in planning of Cox’s Bazar Town by helping in finalizing design of many important structures and saving construction time and cost.