The Kolkatans on Tuesday morning woke up to a reasonable jolt after an earthquake measuring 5.1 hit southern Bengal and adjoining areas at about 6.10 am, IMD sources said.
Though the epicenter of the quake was more than 300 km away and about 91 km beneath the bed of Bay of Bengal its tremors were felt in large parts of Odisha and southern Bengal, sources said.
Tremors triggered panic in Kolkata though there were no reports of immediate damage in the city and its surrounding areas.
"I felt a tremor and watched the ceiling fan sway, and was off balanced a bit.
My head was reeling and initially I thought it could be because of migraine. But then I got alerts of an earthquake from my friends," Basanti a homemaker from Tollygunge said.
Kolkata traditionally falls under seismic zone three and has been gradually progressing towards seismic zone four on account of huge drawing of subsoil water and unplanned urbanisation, Jadavpur University professor said.
A fault passes beneath and through Kolkata but that was not the cause of the earthquake, sources said.
There are four seismic zones with zone five being the most and zone two the least active.
Around 11 per cent of the country falls in zone five, 18 per cent in zone four, 30 per cent in zone three, and the remaining in zone two.
While zone five marks maximum susceptibility being in zone four too is of concern.
Zone three and zone two are relatively of moderate rate in terms of tremors.