More than 54% of Indian landmass is prone to earthquakes. Most residential projects that have been built in the last 5-6 years will be resistant to mild earthquakes registering at around 4 on the richter scale. However, very few would be able to remain standing during a massive quake registering at say 9.
The Indian subcontinent has always been prone to earthquakes. However, it is only the recent earthquakes in Nepal which have made home owners and prospective buyers wonder about the earthquake resistance factor in Indian real estate. Two quakes, a week apart, ripped the beautiful mountainous country to debris and several Indian states and cities felt the impact, as well. In some places, there were even incidents of damage to old structures and ill-planned buildings.
According to geographical statistics, more than 54% of the Indian landmass is prone to earthquakes. The reason for this high amount of exposure is the increasing intensity at which the Indian pelagic plate is driving into mainland Asia. The United Nations and World Bank estimate that by 2050, more than 200 million Indian homes would have experiences earthquakes and storms.
The most vulnerable cities are Srinagar and Guwahati, which have been categorized under ‘very severe intensity’ zones. Apart from these two, 36 other Indian cities have been identified to be vulnerable to earthquakes. These include Kolkata, Dhanbad, Patna, Dehradun, Jalandhar, Jamnagar, Surat, Pune, Mangalore, Kochi, Trivandrum, Chennai, Vijayawada, Jabalpur and Bhubaneswar, among others. Some of these are also among the most important and highly populated cities of the country.
Over the years, increasing concerns about earthquake resistance have led scientists and engineers to invest R&D resources and considerable funding into methods to make modern buildings earthquake proof. Earthquake proof buildings have deep strong base and are lighter in loads than traditional constructions. Special beaming and bracing make them resistant to the kinds of sideways movements that are experienced in the event of an earthquake.
Some of the latest concepts being used to render buildings more earthquake-resistant in many cities are:
• Base Isolation System: Here the foundation of the building is separated from the actual structure using rubber bearings that act as seismic isolators during a quake. During a shake, only the foundation will slide, but the actual construction will stay intact. The rubber bearings also act as shake absorbers and cut down the intensity of the impact
• Dampers: The concept is quite similar to the big shock absorbers used in vehicles. Their job is to dissipate the total energy across the base of the building to keep the top structure safe. Dampers are advisable for high rise buildings and for retrofitting older buildings.
• Levitation: Levitation engineering lifts up the house when an earthquake strikes. The building here is constructed upon a deflated air bag that pumps up during a quake and builds air space of a few centimeters between the house and the ground. This reduces the impact to a great extent.
In India, the Bureau of Indian Standards had a detailed and revised publication for ‘Recommendations for Earthquake Resistant Design of Structures, 1962. According to the standards, buildings that adhere to these recommendations will not encounter a ‘total collapse’ even in earthquakes of intensities as high as 8.0 on the Richter scale.
If you are an existing home owner or planning to buy a new home, you would doubtlessly be concerned about how safe the building really is – especially if it is a modern high rise.
The first thing to know here is that there is no such thing as a 100% earthquake-proof residential building – the best that can be achieved is a standardized level of earthquake resistance.
However, most residential projects that have been built in the last 5-6 years will be resistant to mild earthquakes registering at around 4 on the Richter scale. However, very few would be able to remain standing during a massive quake registering at say 9.
The good news is that in most Indian cities, reputed and established developers are following the accepted local building bye laws and standards for structural safety laid out by the National Building Council (NBC). These are the accepted standards of earthquake-resistance in high-rise buildings, meaning that their buildings will be able to withstand certain intensities of earthquakes.
Such developers follow the guidelines for construction of earthquake resistant buildings as a matter of course. This is not in just a cursory fashion – reputed developers appoint specially qualified engineers who oversee the construction process and make sure that the highest standards of earthquake-proofing are actually being incorporated. Also, builders with a strong reputation for quality construction will at all times ensure that their buildings are built with high-grade steel and that there are sufficient emergency escape routes.
This is yet another reason why one should only by homes in projects built by established developers who have a standing reputation for high standards in their construction norms. If one is still in doubt, one can consult a neutral architect or contractor while the building is still under construction, who will be able to give a fair estimate based on soil cohesiveness and quality of materials and processes being used.