Keep eye on quakes with ear to the ground

Keep eye on quakes with ear to the ground
Dr. P.C. Ghosh

Is there any way to prevent the death and destruction that follows an earthquake? It’s a question that’s doing the rounds all over again after the Gujarat earthquake. Unfortunately, science hasn’t developed to the extent that an earthquake can be predicted accurately.

Accurate prediction would take into account three factors: the time and place of the earthquake and its intensity. It’s possible to isolate areas with a high probability of earthquake, particularly the plate boundary regions and sub-duction zones like the Himalayan foothills, as well as fault zones below the earth.

Scientists can predict that an earthquake of an approximate magnitude can take place in these areas within 50 or 100 years. But the intensity is unknown. The earthquake prone area extends over thousands of kilometres and can take place anywhere. Such a prediction is of no use. It is only after an earthquake takes place that some probable reasons can be assigned.

Several methods are followed in prediction. The prominent ones include micro-seismic survey, geodetic survey, observation of animal behaviour and radon survey.

The micro-seismic survey method monitors small intensity tremors the earth experiences at a place before an coming earthquake. The frequency of such tremors increases and gives an indication of a possible large quake.

The study of gradual deformation of the earth surface (geodetic study) also provides some clues. has been observed that some animals behave erratically a few hours before an oncoming earthquake. But there is no standard method of monitoring their behaviour.

Uranium is present in traces almost everywhere in the soil and in rocks. The uranium series has a gaseous member ‘radon’. Being a gas, it can detach itself from the parent body and migrate in the soil or in the ground water. It is an inert gas and does not react chemically to anything in the surroundings. It remains suspended in water and is released by mere agitation or heating. It has been observed that the concentration of this gas in well waters increases a couple of days before an earthquake takes place.

However, none of these methods can pinpoint an earthquake. All they do is give indications, and they’re not always reliable. Perhaps, the radon method and the study of animal behaviour are more effective than others because they give a signal only some hours before an earthquake takes place.

It’s still not very clear how animals can sense the occurrence of an earthquake in advance. It is possible that their ability to sense very high frequency (ultra-sonic) sound which humans cannot gives them the ability to sense what’s coming. This implies that a few hours before an earthquake, very high frequency tremors are generated which animals can sense. These high frequency tremors may also be responsible for releasing dissolved radon in ground waters.

Instead of measuring radon in well water or monitoring animal behaviour, a direct measurement of ultrasonic waves in deep miles may be more fruitful in predicting earthquakes only a few hours before its occurrence. Unfortunately, not much work has been done on these lines.

Some institutions in India that conduct research on earthquake prediction include the National Geophysical Research Institute (NGRI), Guru Nanak Dev University, Indian Meteorological Dept. (IMD), Department of Atomic Energy (DAE) and Geological Survey of India (GSI).

The North-eastern Council in Shillong made an effort to encourage scientific institutions in India to work on earthquake prediction by providing financial and other help. It was proposed to start an independent institution dedicated to this work.

The NGRI director was entrusted with the responsibility of inviting proposals from other scientific institutions and forwarding his suggestions. But no further work was carried out. What the government needs to do is consider opening a laboratory on the same lines as CSIR labs for research and investigation of earthquakes.

Dr. Ghosh is a former scientist with the Dept of Atomic Energy and an honorary professor of Guru Nanak Dev University and Osmania University