The Hindu : Hidden fault line discovered in Kutch

Online edition of India's National Newspaper
Saturday, Jul 26, 2003

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Hidden fault line discovered in Kutch

By Y. Mallikarjun

The high velocity body (in the shape of an inverted cup) in the epicentre region of Bhuj's earthquake.

HYDERABAD July 25. Seismologists have discovered a hidden fault line in northern Kutch, which is believed to have triggered the devastating Bhuj earthquake in 2001. The seismologists feel that there was a potential for more such fault lines in the region.

Six major fault lines had earlier been found in the Kutch region, also known as the rift zone. They were formed over 120-130 million years and were re-activated when the Indian plate collided with the Eurasian plate. The new major fault line, the seventh, was discovered by seismologists from the National Geophysical Research Institute (NGRI) using, for the first time in the country, an extensive network of digital seismographs in the epicentre region of the Bhuj earthquake. The ``hidden fault line'' has been named north Wagad fault.

The NGRI's Deputy Director, Bal Krishna Rastogi, told The Hindu that studies had led to several other important findings, including an intrusive high velocity body across the entire Kutch region, which might be a magmatic intrusion formed about 65 million years ago. This body rose from a depth of 35 kms up to some 8 kms from the earth's surface. Interestingly, the seismologists also found another aqueous rigid body of low velocity at a depth of 20 kms. Earlier, such bodies were found at a depth of 10 kms near Frankfurt in Germany and the Kola peninsula in Russia.

Explaining the significance of the findings, presented earlier this month at the international conference of `Inter Union Geodesy and Geophysics-2003' in Japan, he said that normally stress occurred due to plate tectonics.

But earthquakes did not occur everywhere and were triggered when stress accumulated at some places. The high velocity body found beneath the Kutch region caused an accumulation of stress, leading to the Bhuj earthquake.

The discovery of the new fault line pointed to the need for a more detailed assessment of the entire Kutch region through geophysical surveys, as there could be some more hidden fault lines. The findings also explained why major earthquakes occurred in the region. The contraction of peninsular India, giving a very low stress rate of 2-3 mm/year, was earlier believed to be incapable of causing large earthquakes. The major earthquake prior to the Bhuj tremor in the Kutch region was in 1819 and occurred along the Allah Bund fault line. The other five major fault lines in the Kutch region are Kutch Mainland Fault, Katrol Hill Fault, Island Belt Fault, Nagar-Parkar Fault and Banni Fault.

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