Wake up call
Are Indian cities safe if an earthquake strikes? No, and the only way to protect residential colonies from devastation is to make builders accountable and insist on quake resistant house, says RAVI KUMAR
THE INTENSE suffering of the survivors in Ahmedabad, Bhuj, Rajkot and other parts of Gujarat has numbed the nation. While the nation gears up to reach out and help, we should be prepared for similar eventualities in the wake of fears that many parts of India fall in highly active seismic zones. Especially cities with dense populations.
For instance, is Delhi or any other small town or metropolitan city safe if an earthquake of high magnitude strikes them? The extent of damage in an urban area if an earthquake of similar magnitude hits it as in Gujarat will be many times more. But are we prepared?
The Government has established many departments to provide safety in case a quake hits Delhi, but there are too many missing links which will render these superficial efforts meaningless. One approach to the problem widely being discussed in the media is about a possible prediction and averting of an earthquake. The Indian Meteorological Department is monitoring the parameters of forces responsible for such calamities, but quake prediction is difficult and averting it is almost impossible.
This phenomena is global and many countries including Japan are coping with it by implementing new technologies to counter the quake. They have conceived quake resistant analysis and are fully equipped to handle a crisis. Alternative designs of structures have also been applied at the ground level. In fact, quake resistant structure is just about five to ten per cent costlier than the unsafe structures which are routinely built in urban areas.
Ahmedabad and Bhuj were destroyed by a quake of the intensity of about 7.9 on the Richter scale. Delhi has not experienced any major earthquake though it is Iying on two faults and is categorised under Zone IV of the seismic zone map with the possibility of a quake up to the magnitude of 8.0 on the Richter scale.
More than 50 per cent of the population in Delhi is living in highly congested and precarious housing structures which can have dangerous consequences even if a quake of low intensity (say 5.0 on the Richter scale) hits the city. Most multistoreyed residential buildings are not designed for floor diaphragm action or ductility requirements. They are
not quake resistant.
The trans-Yamuna residential areas are on the Yamuna bed and microzoning of seismicity in this area has revealed greater susceptibility to future damage. Real estate developers; builders, private property owners and occupants of residential areas are primarily concerned with locality, cost, the area and size of flats. No one really cares for basic architectural safety which goes in the building of a house.
Most apartments with parking in stilt at the ground level have been badly damaged in Ahmedabad. The fragile structures with not inherent protection simply collapsed as the buildings toppled over or crashed. Multistoreyed buildings with parking at stilt on ground floors require special considerations in seismic design but they have been ignored in residential or commercial building.
Most architects and consultants do not provide certified design documents to their clients. Multistoreyed building owners and the district administration should insist for a certified copy of ‘earthquake resistant structure design’ from the architect/consultant to ensure the safety of occupants. This should become a norm for all constructions in every part of the country.
In the absence of a certified design document and sometimes even basic architectural drawing (which are mostly lost after a few years of construction), the designers are completely free under law. Ironically, a doctor’s negligence is liable for action under the consumer protection law, but these architects/ consultants and builders are never taken to task for their negligence. They seem to be loaded with big money and have influential connections. No one can touch them.
That is why the Uphaar tragedy can happen in the heart of Delhi. And witness the injustice: the victims still await justice, while the builders carry on with their building spree.
To save time and gain more money, some designers ignore the safety of occupants because the client is either ignorant or cannot question it legally in court. The extent of damage to human life and property can be reduced by making it statutorily mandatory to follow a proper quake resistant design methodology.
One more area of concern is revision in the IS:1893 for the design of quake resistant structures. Though the draft code was prepared some years back with substantial changes in its provisions, it has not been implemented. Buildings designed with the present Indian Standard code may not be safe when checked with the revised code.
Existing multistoreyed structures can be assessed of their safety based on the design document or construction drawings. If required, strengthening of structures can be done by designing shear walls and diagonal bracings. Infill walls and load bearing walls should be properly panelled and anchored. Lintel bands can tie the walls together to save the wall from falling. It can also provide the benefit of solid infills by following provisions of the Indian Standard codes.
Selection of proper foundation systems based on soil parameters is necessary to make the structure bear future earthquakes. Raft foundations and pile foundations with a framed structure is a safer option.
The duo of consultants and builders usually pass on responsibility for structural failures on each other. Both are equally responsible for negligence. Proper analysis, design, certified design documents and construction drawings are the responsibility of the consultant, while construction is the builder’s responsibility.
Architects can also play a vital role in ensuring the safety of buildings by adopting structure configurations which have inherent quake resistance capacity. IIT Kanpur conducts professional courses to update quake resistance technology.
All over Indian cities and towns, every resident should wake up and check out if he or she is living in a safe building or not. In the wake of the Gujarat tragedy, both the Government and the civil society would do well to build quake resistant structures and see to it that everyone follows the norm. Builders and consultants should be put under legal and ethical scrutiny. This is one way mass tragedies can be avoided.
New Delhi, January 30: THERE ARE five spots in the Capital which have been identified as the most vulnerable to earthquake related disaster, says a study by an engineer. Delhi is sitting atop two big faultiness. The magnitude of the earthquake in Delhi has a noticeable increasing pattern in the years from 1994-1999 exhibiting an intensification of seismic activity’ in the last five years. Building bylaws need to be redefined and government authorities need to take cognizance of these areas while drafting their plans.
Jamia civil engineer Narendra Kumar, drafted this study, by taking soil samples along the Yamuna river and conducting soil penetration tests to ascertain the quality of substrata soils the depth of the water table and its density in the area.
Conducted along Yamuna river, the study identifies the regions of Bhagwan Dass Road, Pragati Maidan, Greater Noida (Sector 37) as well as the soon to be industrialised areas of Narela and Bawana as being highly susceptible to ‘liquefaction’ and included under the ‘critical zone’. Other sites include Siraspur, Supreme Court, Nizamuddin as well as Maharani Bagh.
According to Mr. Sharma, who has operated as a civil engineer in the Gulf as well as Delhi, "One of the major causes of destruction during an earthquake is the failure of ground structure." In the case of Delhi, the area along the Yamuna river is most susceptible to liquefaction. One of the primary reasons for failure of ground structure is loss of strength, which is what brings him to a phenomenon called liquefaction.
Soil liquefaction is a physical phenomenon characterised by a complete loss of resistance.
When a granular material like sand is put to pressure, in the initial stages, the load is taken by the soil particles. These particles are surrounded by their moisture, which becomes viscous on further accentuation of pressure. Soil particles are connected by resistance, but the moisture acts as a disruptive effect on this binding force. Which means that when such a medium is subjected to vibrations like earthquake, it starts behaving like a liquid, he explains. In this case the ground fails.
Failure of ground structure also occurs when there is too much ground pressure built on an area. This, says Mr. Sharma, happens with structures like big dams and reservoirs or water storage facilities as well as large concrete structures, especially in big cities. Stress built up consistently will find release from the first weak spot that it comes across. The Union Territory of Delhi has witnessed as many as 58 earthquakes of different magnitudes in the last 280 years, a maximum of 6.8 on the Richter’s scale.
Given that Delhi does not have a single crane which can lift a load of a 100 tonnes or any other such proper vehicle that can be used for lifting concrete, says Mr. Sharma Delhi government, has to go a long way in its disaster management planes.
BANGALORE, JAN. 30. This time it was Bhuj. But a killer quake is ``overdue'' in the Himalayan region. With the highly-populated Gangetic plain right below, such an earthquake would have devastating effects.
Studies have shown that 50 to 70 per cent of the Himalayan range was overdue for a great earthquake, said Dr. Roger Bilham, Professor of Geological Sciences at the University of Colorado and an expert on seismology of the region. The magnitude of the quake would be between 7.8 and 8.3 on the Richter scale, he told The Hindu.
It was not possible to predict when or where the earthquake would occur. However, the regions with the highest probability of undergoing a powerful earthquake were western Nepal, Kumaon and western Bhutan, Dr. Bilham said. ``Although it is speculative to conclude so, it is possible to argue that we are seeing stresses tightening in the Indian plate, leading to one or more of these great earthquakes occurring in the next decade.''
A paper published in the journal Current Science in 1998 by Dr. Bilham, Dr. Vinod Gaur (now at the Indian Institute of Astrophysics here) and others pointed out that Himalayan earthquakes tended to focus energy towards the northern plains where shaking was amplified by the soft alluvial soil.
In the past 100 years, population in northern India has quadrupled in villages and increased by an order of magnitude in the cities. Some changes in construction practices had not improved the earthquake resistance of buildings. The presence of several large dams in the southern Himalayas posed an additional risk to the people. ``There is thus a substantial increase in earthquake risk from the recurrence of great and moderate Himalayan earthquakes,'' the article observed.
When in 1992 Current Science brought out a special issue devoted to seismology in India, it pointed out that several earthquake- free decades in the Himalayan region had created a sense of complacency and a lack of public concern about their destructive potential. ``Prudence requires that we should be prepared to meet such hazards and take effective measures to reduce their ill- effects,'' it pointed out.
The magnificent Himalayan range, stretching for about 2,400 km in an arc from Nanga Parbat in the west to Namcha Barwa in the east, was created when the Indian plate collided with Eurasia. Since the Indian plate continues to push into Eurasia, it creates stresses which are periodically released in the form of earthquakes. As a result, the Himalayan belt is seismically highly active. Dr. Bilham, Dr. Gaur and others have been using GPS receivers, which can accurately compute the position of any place based on satellite signals, to study the movement of the Indian plate. The GPS measurements showed that sufficient stress had accumulated to drive a magnitude-eight earthquake along at least 50 per cent of the Himalayas, said Dr. Bilham. It took about 15 magnitude-eight earthquakes to rupture the entire length of the Himalayas, according to him.
The renewal time in the Himalayas for great quakes was 300 to 500 years. If it took 300 years to develop enough stress to drive one such quake, there should be one of them happening every 20 years.