Three perceivable indicators of quakes

By M. Malleswara Rao

HYDERABAD, JAN. 31. While the helplessness of science in predicting earthquakes is too well-known, nature itself covers up this deficiency by providing sufficient hints "far in advance" and it is for people and governments to follow them up and take precautions.

Dr B. K. Rastogi, Deputy Director, National Geophysical Research Institute, Hyderabad, India's premier agency engaged in research and in measuring earthquakes, says people may dismiss the suggestion to go by abnormal behaviour of animals and reptiles and sudden rise and drop of water levels in borewells, which are normally seen prior to any earthquake, as nonsensical and impractical but surely, they can't ignore three other visible and perceivable indicators.

They are; radioactive gases that emanate from the earth in clouds of smoke, as noticed in parts of Andhra Pradesh, Karnataka and Maharashtra at the time of the Latur quake, foreshocks that come as a precursor, the kind which indeed were experienced in Kutch region a few days before the Republic day catastrophe, and the property of electrical conductivity acquired by the portion of the earth targeted by stress underneath built up over the years.

Satellites, indigenous or foreign, that see the earth from the skies are of no use to make any prediction. Geologists at the Geological Survey of India, Hyderabad, contend that geological transitions leading to shifting/clash of plates occur over a period of centuries that too in millimetres and such changes may not be visible to satellites in days, weeks, months and years.

Besides, people can be wary about the recurring nature of the earthquakes at a spot. In the case of Kutch, the quake maintained a cycle of 182 years (say 200 years) with the last occurrence taking place in 1819 with the magnitude almost touching 8 on the Richter Scale at that time also. Dr Rastogi feels that the Kutch Rift which is on "west-northwest and east-southeast trend" may have been one of the causative factors of the Bhuj quake.

Dr Rastogi speaks about India's revised map of earthquakes subscribed by his organisation, suggesting that every State Government should go through it. The map divides the country into five zones depending on the degree of "faults and fractures" and the possible magnitude with which the quake may strike. Kutch lies in the "highly volatile" fifth zone along with the entire North-East belt, Bhutan-Sikkim, Garhwal region of Uttar Pradesh, parts of Punjab and Kashmir where the magnitude can go up to or beyond 7. The revised map shifts the entire south--Andhra Pradesh, Tamil Nadu, Karnataka and Kerala--to zone I, II and III where the magnitude expected ranges from up to 4.5 on the Richter to up to 5.7. The Latur region which saw many quakes, is placed in zone IV in which the magnitude can go up to 6.3. The occurrence is taking place for every 200 years in the Himalayas and for every 50 years in the region as a whole.

In Andhra Pradesh, areas in Ongole, Bhadrachalam, Vizianagaram, Srikakulam, Nellore, Anantapur, Chittoor and Hyderabad (Urban) districts have been dubbed "more seismic".

Dr Rastogi doesn't want to join the controversy about the magnitude of the Kutch earthquake. The India Meteorological Department, the country's nodal agency for earthquake data, put it at 6.9 and the US Geological Survey at 7.9 on the Richter Scale.

The scientist who was instrumental in preparing an Earthquake Manual for the Andhra Pradesh Government, advises people not to get scared about the quakes but intelligently be prepared to face them. The foremost thing that people in the prone area have to do, according to him, is to construct shock-resistant houses. Houses or apartments should be built as a single unit connected by at least two or three concrete beams at different heights and with walls, especially in corners, properly dovetailed.

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