Movement of plates caused disaster

The continued movement of the Indian plate, at the rate of two centimetres per year in a north and northeast direction is believed to have caused the recent devastating earthquake in the Indian state of Gujarat. At this rate, seismologists feel, India will plough into Tibet eating into 180 km in the next 10 million years, virtually wiping out present day Nepal. The Indian plate, which is one of the seven major plates beneath the earth which move in a semi-liquid state at the rate of one to 20 cm a year, has been colliding with the Eurasian plate for the last 80 million years. It is believed the Indian continent has continued its horizontal movement towards Tibet. As a result the gigantic Himalayan range continues to grow even now.

Earthquakes in Gujarat have followed a predictable pattern with major tremors reported every 25-30 years – Bharuch in 1970, Dwarka in 1940, Bhavnagar in 1919, Kutch in 1903, and Bhavnagar again in 1872. Scientists at the National Geophysical Research Institute in Hyderabad say the spreading of the Indian Ocean sea floor and the rotation of the Saurashtra region in an anti-clockwise direction causes the earthquakes at the beginning of the plate in the Saurashtra region and its end in the Himalayas.

Says Dr J.G. Negi of NGRI: "The system reactivates in the weak zones every 25-30 years because of this shift." Negi says Saurashtra is criss-crossed by the Cambay rift which runs south to north, the Narmada rift that runs east to west and the Saurashtra rift because it rotates in a westerly direction.

Seismologists at the India Meteorological Department in the capital say the movement of the Indian plate is basically the continuing process of continental rift, the theory which was proposed by Alfred Wegener in 1912, under which it was suggested that 225 million years ago, all major continents of the world formed one giant supercontinent called Pangaea that started to split apart around 200 million years ago forming various continents.

Besides the seven major plates, there are a handful of sub-plates that are on a collision course. Within these plates there are many fault zones which are more prone to earthquakes. Bhuj, which was at the epicentre of the recent earthquake, lies in a similar fault zone.

Ashim Kumar Ghose, senior seismologist at the IMD, the national agency for detecting and locating earthquakes and evaluation of seismicity in different parts of the country, says they have divided India into five seismic zones. Zone V, which is the most vulnerable to earthquakes of a magnitude of eight or more covers the entire northeast region, Andaman and Nicobar Islands, the Bhuj area of Gujarat and pockets in the northern states of Jammu and Kashmir and Himachal Pradesh. The remaining parts of north India, including Delhi falls into Zone IV and is also at high risk.