Dhaka has long expanded faster than it has planned. Wetlands have been filled, low-lying areas built over, and high-rises have been raised that may not withstand a major earthquake. In the second instalment of a six-part series, Star examines how ruptured gas lines, short circuits and crippled water supplies could turn a powerful tremor into a wider fire disaster.

A major earthquake could not only cause widespread building collapse in Dhaka but also trigger catastrophic fires through ruptured gas lines, electrical short circuits and other secondary hazards, experts warned.

They said casualties often rise sharply when fires break out after earthquakes, especially where adequate preventive measures are not in place.

Basic utilities -- electricity, gas and water -- can quickly turn into major threats during a strong quake. Electrical lines can spark short circuits, gas leaks can fuel fires, and damaged water supply systems can leave little water for firefighting.

In a city like Dhaka, where overhead power lines form a tangled web across much of the skyline and gas and water pipelines lie beneath congested roads and neighbourhoods, experts warn that a powerful earthquake could quickly trigger cascading disasters, particularly widespread fires fuelled by gas leaks and electrical short circuits.

“During a strong earthquake, one of the most dangerous secondary effects in earthquake-prone cities is fire,” said Mohammad Abu Sadeque, former vice-president of the Bangladesh Earthquake Society and executive director of the Centre for Housing and Building Research.

He said fires usually start from electrical short circuits. If a quake strikes during cooking hours, gas stoves can also ignite fires. At night, electrical faults become the primary cause. Such fires can spread rapidly when gas pipelines rupture and leaking gas feeds the flames.

At the same time, water supply systems often fail as pipelines break and water drains away, creating an acute shortage. Residents without stored water face immediate hardship, Sadeque said.

Historically, many cities have suffered greater damage from post-earthquake fires than from the initial shaking. In the 1906 San Francisco earthquake, nearly 80 percent of the total destruction resulted from fires, while about 20 percent was caused by building collapse, he noted.

The risk is even higher in cities like Dhaka, Sylhet and Chattogram, where extensive gas pipeline networks run beneath the streets, Sadeque said.

“Ideally, earthquake-prone cities should avoid piped gas and rely on cylinders instead. But in Bangladesh, piped gas systems were introduced long before earthquake risks were widely understood, making the existing network a major hazard,” he said.

“Our electrical system is also highly vulnerable. In many areas, especially informal settlements, electrical connections are poorly installed, increasing the risk of short circuits,” he added.

Sadeque said fires caused by short circuits can be prevented by installing automatic shut-off devices at a building’s main electrical connection.

“Earthquake waves arrive in stages. The first, weaker seismic wave causes little damage, while the stronger wave that follows is responsible for most of the destruction. Automatic shut-off devices can detect the initial wave and cut off electricity before the stronger shaking begins,” he said.

“The same technology can be used for gas and even water lines. Most major earthquake-prone cities around the world use these mechanisms,” he said.

Hospitals also rely on early-warning alarms. During surgery, alarms give doctors time to pause and protect patients. Equipment such as oxygen cylinders must also be properly anchored to prevent them from falling, he added.

“Gas pipelines cannot be replaced overnight, and people will not easily switch from piped gas to cylinders. At the very least, flexible joints should be installed at every bend and connection in gas and water pipelines to reduce the risk of rupture,” he said.

Utility networks, including sewer lines, could suffer severe damage, leading to sewage overflow. Communication towers may fail, while power stations, fire stations, television studios and newspaper offices also remain vulnerable because many buildings have never undergone proper structural inspections, he said.

Calling automatic shut-off systems a low-cost solution, Sadeque said their installation would cost very little compared with firefighting equipment or post-disaster recovery.

“For a city like Dhaka, the cost would be negligible compared to the protection these systems provide,” he said.

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Echoing his concerns, Prof Mehedi Ahmed Ansary of Buet’s Civil Engineering Department said, “After 2015, we proposed an Emergency Shutdown System, where sensors automatically shut off gas and water when vibrations exceed a certain threshold.”

“The technology is not expensive, but the initiative stalled within just 15 days. What we need is strong political commitment and top-level support,” Ansary said, adding that gas supplies must be shut off within 15 seconds to prevent major accidents.

Ahemed Mukta, managing director of Architectural Consultancy, said residents must know the locations of gas, water and electricity shut-off points. These should be clearly labelled and immediately closed in the event of leaks or sparks.

Kazi Md Saidul Hasan, general manager (operations) of Titas Gas, said automatic shutdown would require sensor-equipped valves that close when they detect a certain level of vibration. Alternatively, valves could be controlled remotely from a central control room.

Such a system, known as SCADA (Supervisory Control and Data Acquisition), is not yet in place at Titas, though the company is working to integrate flow-control valves into SCADA in the future, he said.

Currently, main gas station valves cannot be operated remotely during disasters like earthquakes, he said.

Another option is vibration-sensitive automatic shut-off valves, which are also absent from the main network. Only prepaid residential smart meters currently have such safety features, he said.

“We are considering adopting this technology, but it requires significant funding,” he added, noting that all main station valves would need to be replaced, as existing ones are entirely manual.

Following the Narsingdi earthquake, Fire Service and Civil Defence Director General Brigadier General Muhammad Jahed Kamal told The Daily Star that, in addition to firefighters stationed across the country, a 60-member Special Rescue Team has been kept on standby at Purbachal.

“If any fire station becomes unable to operate due to an earthquake, this reserve team will be deployed,” he said.

“To strengthen earthquake preparedness, we are training 62,000 volunteers nationwide. So far, 55,000 have completed the training, while refresher courses are underway,” he added.

While fire service personnel are trained in earthquake preparedness, awareness and post-quake rescue operations, the DG cautioned that a very high-magnitude earthquake could overwhelm the department’s existing response capacity.