At 4.45 a.m. on Wednesday, when a blast ripped through the air of Ekalbara, sending reverberations across, all its terrified residents poured into the village square and remained there for an hour.The 153 families of the village in Dhar district, facing submergence due to the swelling backwaters in the Narmada, had felt the tremors for the second time in the day. Earlier, on September 7 and 9, tremors had again rocked them out of sleep. Terror has gripped more than 12 villages in the Barwani district, and in Ekalbara in Dhar district, as tremors measuring up to two on the Richter Scale have been experienced there since August. This has coincided with the filling up of the Sardar Sarovar Dam, downstream in Gujarat, to its full reservoir level of 138.68 metres for the first time, to test its integrity. Though the dam should be filled up only by October 15, the level had already reached 138.34 metres on Sunday.“The blasts are so loud that they could be heard even 6-7 km away. It’s like one you’d hear from a mine, that’d send birds flying away,” said Bharat Mandloi, 38, a farmer from Ekalbara. “Even at the site of rehabilitation, tremors are being felt. We’ve never experienced them in the region before.”Stating that an expert from the Geological Survey of India had been called to study the phenomenon, Dhar Collector Srikanth Banoth said, “Anyway, the village has been evacuated as it has been submerged by the backwaters. The tremors were light and ranged between two and three on the Richter scale.”Meanwhile, in the Mandil village of Barwani district, 55-year-old Narsingh More said five-six tremors in quick succession within a minute were felt almost every day. “Half the village has emptied, cattle run helter-skelter, and water in wells strangely bubbles after a blast. Many have left behind property in the custody of one or two family members and shifted to relatives in safer villages,” he said. His 20-by-20 feet kuccha hut has even developed cracks. “No one is sleeping indoors at night,” he said. “The authorities say it is because of excess rain, but even during floods in the 1970s, we never felt such shocks.” During a visit to his constituency Rajpur last month, State Home Minister Bala Bachchan said, “Cracks have appeared in the walls of houses, and walls have collapsed in some areas. A temple has caved in at a village. The rising water level in the Sardar Sarovar Dam has created mayhem as tremors are being recorded in the villages of the Narmada Valley.”On the other hand, a senior official of the Narmada Valley Development Authority, when asked, was not aware of reports of tremors and said the Department had not received any official report on it so far. It is an established fact that the region falls in the Seismic Zone 3, a moderate damage risk zone, an official of the Geological Survey of India (GSI) told The Hindu, adding, “Due to excess water percolation underground, gasses need an outlet. Therefore, with their release, blast and mild tremors could follow.”However, kuccha houses or those made of single-bricks may develop cracks, he added. “Overall, these tremors are normal and not a cause for concern. Yet, there needs to be a comprehensive Narmada Valley-specific study to ascertain the cause. The last one in the basin was conducted in 1997 in Jabalpur. If the State government asks for it, we will conduct a detailed study.”As villages in the Barwani district began experiencing tremors, the Barwani District Collector requested the GSI to investigate the underground sound emissions and ground vibrations. The GSI’s preliminary examination noted that these were “earthquake swarms” — localised low-magnitude tremors that could last over a period of time, even months. It recommended that structures be earthquake-safe in the region, as weak houses could be affected even in the case of mild earthquakes. “It is likely that a change in the water table caused by monsoons is creating these jolts. As the events were accompanied by a blast-like sound, their source region may be very shallow,” noted the report.Arun Kumar, part of the three-member team that conducted the investigation, told The Hindu that no visible fractures or changes to the physical landscape were observed in the region.