A report by the Karnataka State Natural Disaster Monitoring Centre (KSNDMC) on tremors close to the Krishnaraja Sagar reservoir (KRS) has found two Quarry Blasting Signatures (QBS) (tremors caused by quarrying) near the crucial dam.
The report follows complaints from residents around the KRS and adjacent villages saying they had heard loud hollow sounds twice and felt micro tremors on Tuesday.
It was suspected that the unscientific blasting at stone quarrying units situated in the vicinity of Baby Bettada Kavalu had triggered this. But, these claims were refuted by the Department of Mines and Geology officials. Later, the KSNDMC was asked to ascertain the cause of sound.
In their report, the KSNDMC has analysed two possible QBS, barely six seconds apart at 9.07 a.m. on Tuesday at the VSAT Enabled Permanent Seismic Monitoring Stations (PSMS), said G.S. Srinivasa Reddy, Director, KSNDMC, in the report on ‘Seismic Data Analysis’ at the KRS.
The signatures came from a radius of around 10.5 km from the KRS at a stone crusher quarry area, Baby Bettada Kavalu, says the report based on analysis by two sensors, Broadband Seismometer and Strong Motion Accelerograph.
“The present record of QBS might be a quarry blasting activity resulting from high amount of explosives. Quarrying activity with uncontrolled explosives create lots of ground vibration,” the report reads, adding that the sounds could also be from the collapse of air cavities due to heavy rainfall.
The report states that the KRS authorities need to check the reservoir regularly for fractures and other civil-related damage on the structure.
The State Dam Safety Committee, in co-ordination with the [Mandya] district administration, needs to inspect/survey the area within a radial distance of 15 to 20 km from the reservoir and propose a plan to regulate any activities which could harm the reservoir’s structure in a longer course of time, KSNDMC report says.
Report sent
According to officials at the centre, the report has been submitted to Deputy Commissioner N. Manjushri. She was not available for comment when The Hindu tried to contact her.
Sources at the district administration said Ms. Manjushri has sent a proposal to the State government seeking blanket ban on quarrying activities in the vicinity of Baby Bettada Kavalu. However, this may be a politically difficult task considering that many Janata Dal (Secular) leaders, including family members of Minor Irrigation Minister C.S. Puttaraju, run the quarries, said sources.