January 27, 2001


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The Rediff Interview/ Seismologist Vinod Kumar Gaur

'Science can tell you when an earthquake will occur. But what then?'

Can we predict where the next tremor or quake will occur in India? Have we invested enough money and manpower on this exercise? Where, on the Indian subcontinent, will the next major earthquake occur?

M D Riti spoke to internationally renowned seismologist Vinod Kumar Gaur -- also a distinguished professor attached to two scientific centres in Bangalore, the Indian Institute of Astrophysics and the Centre for Mathematical Modelling and Computer Simulation -- to find out more about killer earthquakes.

Is there no way that one can predict that a quake like this will occur?

There are three things that you will want to know, as far as an earthquake goes: when exactly, where and how big. And all this with minimum uncertainty. That, I believe, would be a very difficult course, and not possible, because of the great variabilities in the earth's structure and the kind of criticality of the phenomenon.

Critical phenomena are very difficult to predict. They may suddenly nucleate. They may be preparing to happen for a very long time. But exactly when they will actuate is very hard to know.

However, what is possible is to determine is what will be the maximum ground-shaking intensity that a given region will experience in 10,15 or 20 years, and then make sure that all your structures and communication systems are designed as to withstand this.

In Ahmedabad, for example, where tremors killed about 1,000 people, many buildings are quite intact because they have been well designed and properly constructed. So the challenge of science is to be able to assess that hazard, in terms of what is the maximum strength in terms of ground vibrations, and how to design the building to withstand that.

The latter part is something that is quite well known. In this country, there are engineers who can do this if they have the will to do so and contractors who can construct such buildings easily. But so much of our population acts in an ad hoc manner, is self-guided without knowledge.

We can safeguard ourselves against hazards by making a reasonable estimate about what is the level of that hazard. Over a certain number of years, it is then possible to put up buildings that will not collapse at such times.

The challenge really is to make sure that constructions and communication systems can withstand all this. Communication systems determine rescue and relief operations. Right now the communication systems have broken down. You cannot access Ahmedabad. You can certainly design our systems in such a manner that they do not suffer grievous lapses.

Is there any effort to study on an ongoing basis which are the places in Indian which could be prone to earthquakes or tremors?

Certainly there is. But it is like human diagnostics. You have to make a lot of measurements, have a lot of instruments that are densely deployed. Highly sophisticated instruments are now available in the world that can communicate through satellites, bring all the information to a central place where the data can be analysed, like a doctor has a diagnostic centre. If we are able to invest that kind of effort, there is certainly a great deal that we can learn.

The Indian continent is colliding with Eurasia along a boundary where a maximum amount of compression takes place. That's the locale where most of this compression energy is focussed, and released much more frequently than elsewhere. This is the Himalayan region. Four major earthquakes have taken place in this region over the last century. There are parts of this belt which are still unruptured. One suspects that the energy budget accumulated in this region is already reaching rupture point. Therefore, over this decade or the next, it will be foolhardy to exclude the possibility of a major earthquake.

All this is at the boundary. But when you push a continent, there will be little cracks and crevices along which energy will accumulate. This is at a much lower rate, so earthquakes will not take place so frequently there as to create a manifest line of weakness that you will see in the Himalayas, but something that is easily obliterated by geology, human activity and erosion. Whatever has been created over 1,000 years leaves no tracks.

Therefore tracks of earthquakes, which are easily identified at plate boundaries are not so easily identified within the continent. This earthquake is like the Khilari earthquake, which took place within the continent, where the sharp lines or boundaries or zones of earthquakes are not so easily identified. This is our problem.

There are instruments that enable us to do that with perseverance over at least a decade or so. This work was started in this country about five years ago, with our group setting up our instruments at the campus of the Indian Institute of Science. These instruments also incidentally determine, for the first time, the actual rate of movement of the Indian plate towards Eurasia. We have been since trying to ask the question of how this movement is partitioned between different zones within the country.

To some extent that question has been answered particularly with regard to the Himalayan zone. But between here and the south of the Himalayas, there are so many zones where energy could be accumulated. Unless we have a very high density of such instruments deployed, and a large number of groups working on this, we would not be able to solve this problem.

Have your studies shown you any well populated areas that could be in trouble in the near future?

Let me give you some numbers. India moves northwards at the rate of 50 mm per year. About 15mm of this is accommodated within a 100 to 150 km wide zone which is the Himalayas. So 50 mm which is 5 centimetres becomes 5 metres in a hundred years.

In half a century, it becomes 25 metres. Eventually, it is going to break. One important result of our study is that a third of this movement is being used up in compressing the Himalayan belt. Therefore that region has to be washed out. And wherever that energy has been known not to have been spent in so many years, are potential zones for earthquakes.

So from Kashmir to Assam is this 2,400 km belt of the Himalayan arc. Of this, less than half has been broken since we know. What happened before that is not a part of recorded history and so is an area of ignorance. We don't know where in those unruptured centers earthquakes have occurred in the past. There are some conjectures, but not very well proven.

One could say that in all these sectors it has not broken for at least 700 years. If you compute all this, 5 cm a year over 700 years, amounts to about 10.5 metres, as only a third of this is accumulated. 10.5 metres of strain is close to rupture point Therefore, it would be foolhardy to exclude the possibility that that's where the next major earthquakes are going to take place over the next decade or decades to come.

We must make sure that regulatory building codes are enforced in those areas. And that dwellings are safeguarded against the earthquake hazard. And that land use is also similarly regulated, so that landslides, and other such land-wasting processes can be checkmated. Which can be exacerbated by earthquakes, and thereby become a source for disruption of economic and social life.

What about tremors that could cause a loss of life, like in Latur?

Latur was the seat of an earthquake, like this one was. The energy from the seat of an earthquake then propagates in all directions. Because the Indian crust is strong, the energy propagates over long distances in all directions. Even at long distances from the epicenter you feel significant vibrations of the ground, which we call tremors. But we have no knowledge of what are the weak zones in this part of the country.

If we put this global positioning system network into the region, then over a period of 10 to 15 years, we will be able to say where it is happening. Why so much time -- is because the actual deformation or shrinking is so small that it will take 10 to 15 years of measurements to ensure that what you are measuring is above the noise level. But in the Himalayas where it happens faster, you can do that within 10 to 15 years.

Do you think the government is devoting enough money and manpower to studying earthquakes?

I don't think it is. But we cannot blame them for this because you could ask the same thing about human ailments. Is the government spending enough money to study cancer for example or give them potable water? Or trying to provide them living conditions that help them not fall prey to all these debilitating diseases? Is the government doing enough to safeguard the coastal areas from cyclones?

It is a country with intellectual and technological resources that are not plentiful. State of the art global technology now exists to mitigate the disastrous effects of these hazards, but it's a very complex governmental, social, community activity required to accomplish significant progress.

Science can tell you, for example, when an earthquake will occur, where it will fall, which is going to be the uncertainty. But what then? It's the duty of the civil administration to ensure that land use planning is done properly, building codes are followed, that you don't do wiring in such a way that a little vibration will cause a short circuit. So it requires an entire culture of the country to respond in a creative way to a common purpose, and therefore it would not be fair just to blame the government, which just consists of officers who push files.

Scientific and academic organisations have a lot of deadwood. There is something about the sociology of government science that immunises the individual from the necessity to work and intellectually keep abreast of the world. This has created other tendencies to disrupt work instead of promoting it.

Our newspapers and journals also thrive on sensationalism rather than on real work on science. Unless these problems are resolved, the pursuit of science will remain an uphill endeavour.

The Earthquake: The Complete Coverage

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