Mild tremors that lasted up to five seconds, triggered by Namma Metro work at the Cubbon Park underground station at Minsk Square, on Sunday caught many residents of localities nearby by surprise.
Even as the work of removing the supporting beams at the station was under way, people in the high-rises nearby felt the tremors, with some even walking out of the buildings in anxiety.
While the Meteorological Department said it recorded no seismic activity here, Namma Metro sources said a tremor of 0.5 peak particle velocity per second (ppv) intensity was recorded by a seismograph placed in the HAL building nearby.
Source said such tremors were “nothing to panic about as they are common during construction work”. Metro authorities measure vibrations every day, sources said.
The tremors, sources explained, were due to “vibratory hammers” used to remove the steel supporting beams that were installed during excavation.
“I was on the phone when I heard the rattling of the windowpanes and light reflector panels in the false ceiling. The person I was talking to on the phone could hear the rattling. I ran out of the building immediately,” said K.M. Kumar, who was on the third floor in his office near Minsk Square.
Not the first timeThis is not the first time metro work has set off earthquake alarms.
Meteorological Centre Director B. Puttanna said he receives calls every few months enquiring about an earthquake, when it, in fact, turns out to be tremors triggered by underground metro work such as tunnelling or blasting. A few weeks ago, lodge owners in Chickpet had felt tremors as tunnelling progressed under their properties.
The centre’s seismograph does not record tremors less than 1.8 points on the Richter scale, and such tremors were only felt very “locally”, Mr. Puttanna added.
