How vulnerable are our buildings to a major quake?

Constructing buildings without following the Bangladesh National Building Code (BNBC) and not running maintenance according to the code make the structures most vulnerable to heavy earthquakes.

Buildings constructed on land-filled wetlands without piling being done properly to make the soil compact are also at risk of earthquake damage, experts said yesterday.

Talking with The Daily Star last night following the catastrophic earthquake in Turkey and Syria, the experts also stressed the need to identify buildings of Dhaka city to assess vulnerability and making those resilient.

"It is very important to construct earthquake-resilient buildings and for this, all buildings of Dhaka city will have to be tracked. It means authorities concerned will have to assess whether buildings are in good or bad condition," said Mehedi Ahmed Ansari, professor of civil engineering of Bangladesh University of Engineering and Technology.

He proposed a process by which general people can initiate such assessments of the buildings they live in. Under the process, Rajdhani Unnayan Kartripakkha (Rajuk) will issue letters to building owners to do the assessment through a designated company nominated in the letter.

"If the owner and tenants chip in, the cost for this won't be much. After the assessment, the designated company will submit certificates to Rajuk.

"The certificates will be colour-coded – a building marked red is risky, green is safe, yellow or orange is less risky," he said, adding that through this process authorities or building owners would be able to either retrofit the vulnerable buildings or demolish it gradually to avert any disaster.

He said some towns in Turkey followed this system, and the impact of the earthquake was milder in those places.

"We also have to follow the BNBC properly. If we can follow these two things properly, after five years casualties will be reduced significantly during an earthquake," said Ansari, also founder-director of BUET-Japan Institute of Disaster Prevention and Urban Safety.

According to the Comprehensive Disaster Management Plan (CDMP), there are five major fault zones -- Madhupur Fault, Dauki Fault, Plate Boundary Fault-1, Plate Boundary Fault-2 and Plate Boundary Fault-3 -- in the country from where 7 to 8.5 magnitude earthquakes could be generated, said Ansari.

"If an earthquake measuring 7 on the Richter scale generates from there, many buildings of Dhaka will be damaged," he said.

Ansari said the Turkey earthquake has killed a huge number of deaths as many buildings have collapsed.

The most powerful earthquake in nearly a century struck Turkey and Syria on Monday, killing at least 4,300 people, levelling buildings and causing tremors that were felt as far away as Greenland.

Stressing the need for proper implementation of the BNBC and ensuring the requisite quality of a building, Buet Professor Munaz Ahmed Noor said those who construct their buildings following BNBC are comparatively at less risk of damage from earthquakes.

"We have to construct our buildings and maintain quality to stay safe during earthquakes but unfortunately many of us do not follow it and we also do not have the skilled manpower to check buildings properly," he said.

He said authorities like Rajdhani Unnayan Kartripakkha, Khulna Development Authority (KDA) and Chattogram Development Authority (CDA) are implementing the BNBC but a single authority is necessary to implement it so that all the big cities can work in a coordinated way.

With this single authority the BNBC will be more effective and functional, he added.

Munaz said Rajuk stores the structural designs of buildings, but it has neither the capacity nor the authority to give approval or direct that designs be changed. It keeps the designs as a matter of record.

In different countries around the world, they have pre-selected private companies who check the structural designs and then give approval for the buildings, he said.

Maximum housings of Dhaka city have been constructed filling wetlands or lowlands for which the buildings constructed on the filled-up lands are most vulnerable for liquefaction. If a building is not designed properly or constructed without properly piling it may fall during a moderate to heavy earthquake, he said.

An engineering council is also required to bring the engineering profession under quality but there is a huge lack of it which affects the quality of a building, he said.