'Seismic' data study equipment designed

With the conservation of environment assuming profound significance, scientific study using explosives is also prohibited.

This calls for alternative methods and a recent one is ‘Seismic Signal Source’ or free falling weight drop system, an indigenous equipment to study lithology (below the ground) that is beneficial for building construction.

M Balakrishnan, director, Geo-physics, Geological Survey of India (GSI), Mangaluru, has designed the equipment, along with his junior technical assistant Anil Kumar P V (now retired). Interestingly, Balakrishnan is nearing his superannuation and the particular device can be termed as his ‘parting gift’. He is also planning to patent the same at both national and international level.

Balakrishnan told reporters on Thursday, “Circular weights from minimum of 50 kg to maximum 170 kg shall be dropped from a height of over seven feet on the metallic iron plate placed on the ground. The impact on the earth’s subsurface produces seismic waves, enabling the 24 channel geo-phones linked to computerised receiver system, to pick up the signals. It will help understand lithology; be it rock or water source forming different layers beneath the surface to a maximum of 100 to 150 metres depth.”

No noise, jerks

He claimed that, it is also environment-friendly as it neither produces noise nor jerks (due to shock dilating technique), but registers noise-free data, unlike explosives used earlier. It is also easy to transport and detach and assemble. It comes in handy, before taking up any construction activities, to assess the strength of the soil, clay and other sources beneath the surface.

Balakrishnan said, while 24 channel geo-phones were purchased from the US, the pre-designing was conducted at Nagpur. The field trial was conducted at Chitteri in Kasargod, Kerala, where a bridge is being built.

Earlier, whenever such studies were conducted, explosives were used for the purpose. A vacant site away from human habitation was to be identified and a hole drilled till five to 10 metres below the ground to put the explosives. They not just blasted with a huge sound, but also caused jerk, sometimes leading to cracks on any buildings nearby.

Taking all these factors into cognisance, since 2007, alternative methods are being deployed to carried out the study.