City in siesmic danger zone

City in siesmic danger zone
Vijay Times

Seismically safe Bangalore now suddenly appears to be in the danger zone.

And guess what? The risk factor is much higher than before with the population booming and haphazard construction activity targeting dried lake beds to construct buildings.

A five-year research on Bangalore’s susceptibility to earthquakes and how it would be affected by a major tremor has led to researchers prescribing that seismic threat level for the City be upgraded.

The study, conducted by Prof T G Sitharam of civil engineering department of Indian Institute of Science (IISc), and his three students has shattered the myth that a major earthquake in Bangalore and surrounding region cannot occur.

It has found even a moderate intensity earthquake could cause severe damage in Bangalore, which despite being located on a rocky terrain, has in the last 20 years seen buildings coming up on silted lakes/ tank beds.

A German insurance company, Munich Re Group, in its investmentguiding study on Indian metros, indicated a 6.5-magnitude earthquake in Bangalore could lead to an economic loss of $3 billion, besides a huge loss of lives. “A small quake underground can amplify at the surface and buildings standing on lake/tank beds would be the worst hit,” explained Sitharam.

The study conducted as part of seismic micro-zonation of the region around Bangalore, identified ten faults running through Bangalore - one running right under the IISc.

The vulnerable zones identified are Mandya-Channapatna-Bangalore (around Arkavati river), southwest Bangalore near Koramangala, and north-east area of the City near Hebbal.

The research also found increased seismic activity in the southern plateau, hitherto found to be seismically safe.

Sitharam said, “We are over-confident about Bangalore’s safety. Our bore-hole and surface sensors have sensed many tremors of late - one, just two months back.” Sitharam, also a ‘Young Scientist’ awardee, said the research involved studying 950 boreholes (two in IISc itself) with an average depth of 15 metres within a 300-km radius of Bangalore. “All faults and lineaments were identified based on seismologial map of India and remote sensing images and a seismic hazard study was done.” Interestingly, though south India has not had major quakes over centuries, very little data is available.

The Indian peninsula is pushing against the Eurasian Plate at a rate of 5 cm per year. Experts say strain builds up, releasing it anywhere, anytime.