Seismic activity to blame?

By Our Staff Reporter

TUTICORIN, JUNE 28. Even as the railway authorities and experts continue to study the cause of the Kozhikode train accident which claimed 51 lives, a noted geologist in the port town says the Kadalundi tragedy might have been triggered by geological activity.

Prof. N. Ramanujam, Head of the Department, Geology and Research Centre, V. O. Chidambaram College, told The Hindu here that the tectonic history of the area showed that the entire west coast, especially along Kerala- Karnataka, encompassed the `north west- south east trend fault systems.'

Most of these faults were regional in nature and continued along several km, while others were local and ran for short distances, he said. The fault systems developed during the time of separation of Madagascar from the Indian land mass. The deep- rooted faults were inactive but recent seismic activity in the sub-continent had reactivated them in this part.

The fault zones served as easy pathways for the movement of water, Prof. Ramanujam said, adding that the downward percolation of water decreased the shearing strength of the rocks, besides increasing the pore water pressure in the sub- surface condition. This had resulted in the subsidence of land mass. The same had happened in the Kadalundi area. Referring to reports that in the vicinity of the accident site, many wells had subsided, he said this might be due to the increase of pore water pressure.

The pier of the bridge might have sunk because of the subsidence of land due to increase of pore water pressure caused by the recent rains in that region.

Recognition and delineation of active faults and analysis of historical records of the past occurrences were important for ensuring the safety of bridges in future, Prof. Ramanujam said.

The Professor suggested that to determine the strength of the bridge's foundation, scientific evaluation techniques such as vertical electrical soundings and piezometric level could be carried out in the affected area.

Determination of ground strain, engineering properties of the foundation material and liquification potential of foundation soil or sediments should also be studied.

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