On shaky ground for faults of our own

Swiftly launching rescue and relief efforts in Nepal, India emerged as a leading nation in disaster response, Union Minister of State for Home Kiren Rijiju told Parliament last week. Planes were on their way to Kathmandu in less than an hour after Prime Minister Narendra Modi chaired a meeting, he said.

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Technology was extensively used to respond to the natural calamity and the 10,000-strong National Disaster Response Force (NDRF) was ready to meet any situation round the clock, Rijiju added. India’s prompt response won appreciation, and rightfully so.

Since the National Disaster Management Act in 2005 and creation of the National Disaster Management Authority, India has come a long way in post-disaster management. But many remote quake-hit areas in Nepal are still awaiting relief, eight days after the disaster. 

As per some experts, India’s response was “good but it is still not accurate enough to provide relief to remote areas in time”. So far as the pre-disaster protocol is concerned, it leaves a lot to be desired. If the “big one” strikes, it may be catastrophic, warn the experts.

India’s haphazard urban development and complete disregard for building laws in highly-populated areas would ensure that. As per the vulnerability Atlas of India published by the Building Materials and Technology Promotion Council, 58.6 per cent of India’s land is prone to quakes, 8.5 per cent is vulnerable to cyclones and 5 per cent to floods. Many parts are in the high seismic activity zones 4 and 5.

Nepal is among the world’s most earthquake-prone regions because it lies at the head-on collision between two active tectonic plates — Indian and Eurasian,  both of average density, both unyielding. The subcontinent is slowly sub-ducting under the Eurasian plates. In turn, Asia is being pushed upward, adding to the Himalayas. The Pashupatinath Temple in Kathmandu, which continues to stand unharmed even as buildings, historic and modern, have crumbled, can serve as an example of quake-resilient construction for urban planners, says Prof Devesh K Sinha, Head of the Geology Department, Delhi University.

Waiting for the big one

Several scientists suspect that the 7.9-magnitude great shake in Nepal was unable to unleash the stored strain, accumulated for years due to the active below-the-surface movements in the region. A 2001 research by geophysicists Roger Bilham, Peter Molnar and Vinod Kumar Gaur of the Indian Institute for Astrophysics warned that at least one 8.1 to 8.3 magnitude quake, and perhaps as many as seven, were long overdue in the Himalayas.

Broadly, the suggestion is that the quake hazard increases with time since the last big ones on certain faults or plate boundaries. The theory has subscribers, and also detractors.

Seismic gap is a segment of an active fault known to produce significant earthquakes, but has not moved for an unusually long time when compared with other segments along the same structure. One side says over long periods of time, displacement on any segment should be equal to that experienced by all the other parts of a fault. 

Areas which experience many small quakes may not get the large one in comparison to the long silent ones.

Debunking it, many geologists believe the fault could be stronger, requiring much more tectonic stress to break it. Or perhaps tectonic forces, or stress, around the area get reduced by activity in the neighbourhood. Scientists have been waiting for a great earthquake to strike the Tokai region, southwest of Tokyo, for long, they argue.

Quakes do not kill, buildings do

“Being prepared is the only way. India has some very good building rules and regulations, including a code. If they are followed, a disastrous aftermath can be avoided,” says Prof Sinha. By releasing the energy accumulated in a long time, an earthquake in fact gives the area relief from stress. 

Release of seismic energy is a natural process, only the frequency with which it happens is random. “In case a high-magnitude earthquake happens where there is no population, no damage will be caused. But it would be catastrophic if it happens where the population is high and preparedness is low,” says Prof Sinha.

Records suggest that two persons died when Gurgaon was hit by a quake in 1960 at the time when it was still a village. But today, any event touching 6 on the Richter scale could prove disastrous, given its haphazard development growth with little or no regard for regulations. 

In the Bhuj earthquake (2001), Ahmedabad suffered massive damage even though the epicentre was 300 km away. Reason: No preparedness. 

Prof Sinha explains: “Earthquakes are frequent in Japan but buildings are constructed in a way to absorb the energy. The design of Pashupatinath temple should provide clues about the kind of structures suitable for the region. An earthquake of high magnitude releasing massive energy will cause no damage where buildings are designed to absorb the energy.”

In other words, damage depends on several factors such as subsurface geology along with adherence to building codes. Latur in Maharashtra was not proclaimed an earthquake-prone zone, but it still saw one. There are shadow zones along some very active faults in Varanasi, for example, which have seen very little seismic activity. 

Preparedness for earthquakes

India is working on microzonation of different parts to improve urban development planning. Work has been completed for some cities like Delhi, Guwahati, Bengaluru and Ahmedabad. 

It is the government’s effort to take effective measures with proper research to minimise risk to buildings in the event of an earthquake.

Dr AK Shukla, former head of the Earthquake Risk Evaluation Centre and part of the microzonation process, calls Seismic Hazard and Risk Microzonation (SHRM) among the most effective tools for earthquake risk evaluation and generating database for planning pre-earthquake disaster management.

“There are two aspects to planning — pre-earthquake and post-earthquake. Since the formation of the NDMA, we are much better prepared. But so far as mitigation is concerned, a lot more needs to be done,” he says. “When the ground moves, acceleration is generated. So a value is given on how much will be the acceleration in an area in case the ground moves due to an earthquake. We have been able to put together the most accurate data for Delhi. However, the probability with which it will happen needs to be factored in to make it more robust and dynamic,” he adds. 

Microzonation is one aspect, but it should also be reflected in building plans. Public awareness is equally important. For example, how many people who book a flat ever bother to find whether claims made by the builder in the brochure are being followed? Does anyone check whether a structural engineer is involved in the construction of a building?

“Rule and regulations are there but most people do not bother to find out whether they are being adhered to, whether earthquake resistance material is being used,” says Shukla.

The microzonation process, he adds, will help in bringing area-wise changes in building bylaws to ensure quake-resistant measures in the structural designs. “But adherence to laws will ultimately depend upon the civil society,” he points out. And there lies the real challenge. 

India has been divided into four seismic zones. Many parts lie in the high seismic activity zones 4 and 5.

Zone 5 comprises the entire northeastern India, parts of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Rann of Kutch in Gujarat, part of North Bihar and Andaman and Nicobar islands.

Zone 4 covers remaining parts of J&K and Himachal, Delhi, Sikkim, northern parts of Uttar Pradesh, Bihar and West Bengal, parts of Gujarat and small portions of Maharashtra near the west coast and Rajasthan.

Zone 3 comprises Kerala, Goa, Lakshadweep islands, remaining parts of UP, Gujarat and West Bengal, parts of Punjab, Rajasthan, MP, Bihar, Jharkhand, Chhattisgarh, Maharashtra, Odisha, AP, Tamil Nadu and Karnataka.

STANDING GROUND

• No scientific technique is available to predict the occurrence of earthquakes with a reasonable degree of accuracy.
• The earth is moving, leading to continuous movement of rocks below the surface. Tectonic forces at work within the rocks create large faults, resulting in the release of energy, which in turn leads to eruption of volcanoes and earthquakes.  
• During an earthquake, a building experiences transverse and longitudinal vibrations. As the ground moves randomly, the top weight should vibrate accordingly.
• Buildings or high-rises constructed with specified material grades and designs to ensure it moves as a single unit in the event of an earthquake will absorb any impact due to uniformity of the structure. 
• All Delhi Metro structures are completely safe in case of any seismic activity. 
• The National Building Code and BIS norms prescribe parameters, designs and criteria for buildings. The problem is implementation. Any construction that passes through stringent municipal regulations with honesty will be safe in the event of an earthquake. It just costs 4 to 5 per cent extra to make a building earthquake safe.
• High-rises are made of concrete and not bricks alone which make them stronger. But deviations like adding rooms or balconies change the stability factor.
• Structures designed by government housing boards are likely to be safer provided original plans have not been tampered with. Unauthorised structures are also risky.

If a prediction was possible, we would have cautioned people. Speculation about the ‘big one’ is because the last major event occurred in 1934. I think the Nepal quake has released the pent-up energy. We are living in a vulnerable zone. But worrying does not help. Be cautious, be prepared. A lot of material is displaced in a quake, which takes time to reach its original place, resulting in the release of energy and aftershocks. 

Laksman Singh Rathore, Indian Meteorological Department Director-General 

India needs to go in for strict implementation of quake-proof construction norms. The Indo-Gangetic plains could suffer the worst as the seismic wave gets amplified in the sediments of these plains. Strict civil engineering codes must be implemented and no new construction allowed without it. Even in old structures, reinforcement techniques must be undertaken

BR Arora, former director, Wadia Institute of Himalayan Geology 

It is not possible to predict the timing of an earthquake’s occurrence. However, preparedness is the key to minimise earthquake losses both in terms of life and property. Strengthening mitigation measures is the only solution

Dr Sushil Kumar, WIHG expert in earthquake studies

Earthquakes are totally unpredictable and sensitising society is the answer to the challenge. Quake-proof constructions is the need of the hour. The level of lack of awareness can be gauged by the fact that geology as a subject is introduced to students only at the college level

Dr Vikram Gupta, WIHG specialist in geology engineering

The Nepal earthquake could lead to more of breaking of glaciers and landslides in the Himalayan region. The tremors could have loosened up the soil and rocks and a little disturbance can trigger landslides. Remember the deluge in Kedarnath shrine by bursting of Chorabari glacier

Dr DP Dobhal, WIHG scientist