SHILLONG: The city’s proximity to seismic fault lines makes it prone to earthquakes while haphazard construction of buildings, congestion and dearth of open spaces only add to the risk.
“When it comes to Shillong’s proximity to these fault lines, we are still in a dangerous zone. It does not matter where the 1897 event was and maybe a future event will be, all these potential locations may have a significant effect on the building stock of Shillong,” Dominik Lang, head of the department of earthquake hazard and risk at Norwegian Seismic Array (NORSAR), Norway, told reporters on the sidelines of a function here.
“Urbanisation has a negative effect because urban sprawl means that people move away from open space living conditions,” Lang said.
According to him, the living condition is basically a traditional building typology made out of wood. People migrate to the city that have high-rise structures constructed in a fast manner and “fast means diligence is missing.”
“Fast construction is not a good thing and coupled with congestion of buildings and lack of open spaces, has a dramatic effect,” he said.
Commenting on the scenario in Shillong, he said, “I cannot judge how well the city’s earthquake preparedness is but what I know from other parts of the world where you have similar hilly areas, you have a number of effects you need to take care of.
“One of the effects is that building effects that are generally located on slopes are highly vulnerable…. more vulnerable than buildings that are built on flat terrain,” he added.
Lang said the topography was adding to the congestion and roads are narrower and congested. “From a disaster mitigation point of view, it always poses extreme challenges during a disaster,” he said.
“Buildings located on slopes are very vulnerable because they are very irregular. The geometric feature of the slope does not allow your building to be regular in plan or elevation and your foundation is at different levels, which means that at different parts of the building, there are different types of earthquake actions,” Lang said.
Stating that construction in hilly areas was challenging, especially in respect to earthquake resistance, he said, “There are risks of earthquake-induced landslides posed to a house located on the foothill of an unstable slope.”
Referring to the North East region, Lang said, “There are a number of fault lines that are mapped and well documented and I am sure there are geological features that have not yet been documented because, so far, for North East India, not many studies have been assigned.”
“The problem is that internationally it has not received the kind of attention that you would wish, not because it is about North East India. It is simply because recently we didn’t have such dramatic events that we have seen in other parts of the world, the recent one being in Mexico,” he added.
Lang said the 1897 event is very well documented and that recording instruments did not exist at that point of time as recording of earthquake started at the beginning of 1900 but not in North East India.
He informed the information as to which fault line was responsible is basically based on macro seismic investigation.
Macro seismic investigation is not based on instrumental record but more on the people located on different sides within Meghalaya and Assam and how they felt the earthquake and the kind of shaking they reported.