Earthquake in Rayagada: Probable induced causes could be mega dams and excessive mining
Badal Tah,Odishabarta
Rayagada, March 4: According to the National Centre for Seismology, during wee hours at about 5.05 AM last Friday mild tremors of an earthquake measuring 3.8 in Ritcher’s scale jolted Kashipur block of Rayagada and Bandhugaon, Narayanpatna, Laxmipur and Dasamantapur blocks of Koraput, which are adjacent to Kashipur. The tremors lay cantered at a place 16 km of Koraput’s Laxmipur. People ran out of their houses in panic. The quake lasted for few seconds and was at 5 km depth. There was no report of any damage or casualty.
The seismic activities can be natural or may be manmade and induced. There are mega dams with water reservoirs in undivided Koraput district namely Kolab, Machhkund, Indavati, Balimela, etc and are not very far from the epicentre of the present quake. Various researches say that the construction of dams creates a huge water reservoir in which a large portion of land is submerged.
Thus, these dams cause excess water pressure in the micro-cracks and fissures in the ground near or under the reservoir. Due to this excess pressure, the water seeps into the ground and lubricates the rocks. In the worst scenario, when the water pressure is very high, the water reaches the fault planes and lubricates them. This lubrication reduces friction between the tectonic plates, thereby causing the slipping of plates over one another. Hence, in this way dams construction can trigger an earthquake. When the water level of a reservoir is raised, pressure on the underlying ground increases; when the water level is lowered, the pressure decreases. This fluctuation can stress the delicate balance between tectonic plates beneath the surface, possibly causing them to shift.
This is known as Reservoir-Induced Seismicity (RIS): The most widely accepted explanation of how dams cause earthquakes is related to the extra water pressure created in the micro-cracks and fissures in the ground under and near a reservoir.
A seismic event may be caused by mining activities also-both open cast and underground. There are several examples in the world. There are several mines in and around the epicentre Laxmipur. In Kakirigumaa of Laxmipur block, the bauxite mines owned by OMC supplies ores to VEDANTA. Adjacent to it, Navaratna Company NALCO has also the mining activity. In Kashipur, Utkal alumina is extracting bauxite ores. There are greenfield mining areas in Deomali, Kutrumali, Sijimali, Kodingamali, Sasu-Bohumali, etc in & around the epicentre.
“We need to redefine development in the present context & strike a balance. The ball is in our court & we only know where, when & how to move ahead or put a full stop”, said Dr Debajit Mishra, ex-senior geologist & scientist, Odisha Remote Sensing Application Centre.
