Seismic activity may last for a week

By T. Ramakrishnan

CHENNAI, SEPT. 26. Though the meteorological department does not anticipate any ``major aftershock'' in the wake of Tuesday night's quake that rocked many parts of southern States, it has said the seismic activity may continue for a week or so.

The Deputy Director-General of Meteorology in charge of the southern region, Mr. A.K. Bhatnagar, told presspersons today that ``normally, tremors of this scale do not cause any major aftershocks. Even if there are any, they will be mild''.

Pointing out that there was an aftershock last night which was mild, he said the second tremor was recorded at 10-37 p.m. Its magnitude was in the range of 3 to 3.5 on the Richter scale. ``Even, we in the meteorological office did not feel it. There may be some more such tremors that may occur for a week''.

Most parts of Tamil Nadu fell under the Zone-II of the country's Seismic Zone. This meant that they were ``relatively safer'' areas. A portion of the State, in and around Coimbatore, had been designated Zone-III, which covered Kerala too. But the most vulnerable parts of the country included the Kutch region of Gujarat, the northeast and some pockets of the Himalayan region.

Asked whether there would be another earthquake in Tamil Nadu in the near future, he said, ``I will not rule out the possibility of one more quake though such a tremor will not occur in the same spot''.

Appealing to the public not to panic and not to be carried away by rumours, Mr. Bhatnagar said the State had never experienced an earthquake with the magnitude crossing the six- mark on the Richter scale. The highest one was a quake of magnitude 6 that occurred 101 years ago (February 8, 1900) in Coimbatore region. In recent years (since 1998), Salem and Dharmapuri region suffered tremors whose magnitude did not exceed 3.5 on the Richter scale.

To a query whether the successive failure of monsoons and the consequent indiscriminate and continuous drawal of groundwater caused Tuesday's tremor, Mr. Bhatnagar said the fact that the quake's epicentre was in the sea removed such a possibility. Moreover, ``an earthquake of this scale could not have been caused by these factors''.

Asked whether the tremors experienced in different parts of Tamil Nadu since December last would result in the State being shifted from the present zone to a more seismically- vulnerable zone, Mr. Bhatnagar said, ``hopefully not. We do not normally decide merely on the basis of one tremor. The demarcation of zones is done after examining the past data collected over 100 years and seismic surveys''.

However, he hastened to add that the seismic status of the part of Maharashtra, which was originally considered a safe zone, was changed after the 1993 Latur quake. Mr. Bhatnagar also said there was no interconnection between any monsoon or month and the occurrence of quakes.

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