Cities under threat of severe earthquake

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DESPITE Bangladesh sitting atop an active earthquake zone, the same kind of geologic feature responsible for the 9.0 magnitude earthquake in Japan in 2011, most of the buildings in the city are not tremor resistant and the authorities are nonchalant to that also. As per a national daily, some Fire Station buildings and office buildings of international organizations in the city and some 300 garment factories across the country have undergone seismic retrofitting. But residential buildings, educational institutions, shopping malls, hospitals and government offices which remain crowded still remain out of the scope of retrofitting activities that pose a deadly risk to be collapsed during a 6-7 magnitude tremor. Definitely, retrofitting is costly but lack of awareness is high. Government and social institutions should create awareness across the country while structural engineers, social well offs, and development partners should offer low cost retrofitting.
Scientists said a 250km area may be spring-loaded with significant levels of tectonic strain that had been accumulating for more than 400 years beneath the zone. If or when that energy is released, Dhaka could face catastrophic consequences as the sediments on which the city is built on might amplify the seismic waves. The calamity could be much worse because of the city’s high population density and poorly constructed buildings. A 7.5 magnitude earthquake might cause deaths of 88,000 people and collapse of 72,000 buildings in the capital.
Earthquake retrofitting helps to stiffen walls and it prevents buildings from collapsing during seismic shokes. Bracing is accomplished by attaching structural-grade plywood tightly to the wall framing. The entire process costs upto 40 percent of the original spending for the building construction. This measure is very crucial for Dhaka as experts say the city is highly vulnerable to earthquake disasters as preparedness to tackle them still remains somewhat average.
Happily, the Public Works Department has taken up an Urban Building Safety Project to retrofit six fire stations and build three more, while Rajdhani Unnayan Kartripakkha (RAJUK) has taken up Urban Resilience Project to identify risky buildings in its first phase and to retrofit the riskiest buildings in the second. According to the RAJUK project, preliminary vulnerability assessment would be done on schools, colleges, hospitals and important establishments like Airports, Bangladesh Bank buildings, and others. Bangladesh Housing and Building Research Institute is working with the assistance of JICA to develop a local technique of retrofitting for cost optimization.
As per retrofitting the residential building is a solution to make the building earthquake resistant. If the cost becomes 50 percent of the building, it would be wise to demolish the structure and reconstruct the building. Buyers should check the systemic structure when planning to buy flats, while the builders should construct tremor resistant buildings for avoiding calamities. In no way, the City fathers as well as the dwellers should not ignore the threat of such natural calamities over which human has no control whatsoever. It is always wise to remain alert.
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