Published on: 11/1/2015IST
~#cty#~ won't survive a tough quake as seismic safety has long been ignored: India's leading seismologist
Stilt buildings like Vikas Sadan, high-rises, DDA flats, malls, and flyovers and bridges that aren’t maintained regularly are most vulnerable, points out Arun Bapat
"Mobile towers are erected in the corner of the terrace which is highly dangerous. These towers should rather be erected on columns of buildings."
For the second time this year, South East Asia was rocked by a high-intensity earthquake that killed hundreds and affected thousands of people.
Earlier this week, when a powerful quake shook Hindukush region in Afghanistan, Pakistan and several parts in North India including Delhi, Uttar Pradesh and Jammu and Kashmir were also jolted by strong tremors. Loss of life and property was also reported from several parts of Kashmir valley.
The disaster reminded the Asians of the horror of Nepal quake reported in April, deemed to be one of the worst quakes that hit the neighbouring country in 80 years.
While recent quakes did no damage in Delhi-NCR, experts maintain that national capital remains vulnerable as it falls in Seismic Zone IV which has fairly high seismicity.
All that’s vulnerable in Delhi
India’s leading seismologist Arun Bapat, who had predicted the Mexico earthquake reported this year apart from 2004 Indian Ocean Tsunami much before it happened, further warns that North India, especially, urban centers, are at high risk.
Bapat had predicted 2001 Indian Ocean Tsunami much in advance
“For an area like Delhi NCR which falls in Seismic zone IV, an earthquake of magnitude 7.5 was enough to cause huge devastation. But fortunately, the epicenter was far in Afghanistan. Had the epicenter been in Himalayas, these tremors would have caused widespread damage in Delhi and all other urban centres,” the expert says and underlines, “The stilt buildings like Vikas Sadan, high-rises, DDA flats, malls, and flyovers and bridges that aren’t maintained regularly are most vulnerable.”
Why stilt structures would fail in event of earthquake
Bapat, who is currently serving as Associate Scientist at International Volcano and Earthquake Prediction Center (IEVPC), also points out that amid urbanisation boom and population boom, mushrooming of stilt structures and high-rises puts lives at risk in event of earthquake. In a densely populated country like India, tier 1 and tier 2 cities are at a higher risk.
Former Head, Earthquake Engineering Research Division at the Central Water and Power Research Station, Pune, Bapat had recently presented a paper on stilt structures in Australia explaining why these structures would fail at the time of earthquake. “When any building starts vibrating under seismic force, the stress wave starts from top floor and goes down to earth. From top floor till the first floor, the area of cross section remains uniform, but when waves comes to the stilt floor, entire load comes on columns. If we take the area of each floor as hundred, then the stilt floor’s area is about 3 percent or lesser,” he elaborates.
Mobile towers are being erected the wrong way, says expert
Bapat also thinks that mobile towers that that are erected on the terrace of houses and buildings can pose a great threat if Delhi is ever hit by a high-intensity earthquake.
“As per the engineering requirements, the towers should be fixed to the columns of the building. But in most of the cases, the towers are erected in the corner of the terrace which is highly dangerous,” he points out.
Talking about the possibility of frequent earthquakes in region, Bapat shares, “According to Geological Survey of India (GSI) in 2007, the probability of occurrence of such an event is as high as 0.986. This value must have increased in last few years.”
How Delhi had a close escape this time
Delhi escaped from the damage in the recent earthquake because the Rayleigh waves (surfaces waves that travel as ripples to areas far away from epicenter) were weak. The areas of Afghanistan and Pakistan witnessed heavy damage despite having no tall buildings because Shear Waves (a type of seismic wave that remain confined to region near epicenter) were very strong.
“If such an event occurs, there could be heavy destruction in NCR. The Shear waves won’t cause much damage here because epicenter would always be a bit far from here. But Rayleigh Waves will be the cause of destruction,” warns Bapat.
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