NEW DELHI: Frequent tremors in the North Eastern region and others parts of the country, even if mild ones, could be precursors to a major earthquake in the high sensitive Himalayan zone, according to the Geological Survey of India (GSI).
These mild shocks have occurred due to foreshocks and swarms, a top official of the GSI said, and warned that frequent tremors were a matter of concern in the subcontinent, where several areas are prone to major seismic activities.
Dr Sandip Som, the deputy director general of GSI, also said foreshocks — mild tremor preceding earthquakes — or swarm activities — series of earthquakes — indicate release of tectonic stress and strain.
This happens during the continuous deformation process, and a detailed study of these jolts could help predict if a significant seismic event is in store.
“These minor earthquakes are mainly clustered in the Northeastern and Northwestern Himalayan region, around the Delhi-National Capital Territory (NCT), western Gujarat and Western Maharashtra areas which have been demarcated as seismic zones IV and V,” the geologist said.
In the past, too, low-magnitude earthquakes have been recorded in these regions. According to the GSI scientist, earthquakes in the Northeastern and Northwestern Himalayas occur along the plate convergence zones — between India and Eurasia.
Explaining the reason behind the frequent tremors, the geologist said any earthquake depends on the strain and stress build-up of an area.
“Main strain and stress build-up areas have been noted along the convergence zone between Indian and Eurasian plates. Due to continuous plate movement, stresses build up in this area. Moreover, there are around 30 water reservoirs which also enhanced water load in the reservoirs increasing pore pressure and stress, triggering earthquakes,” he said.
The GSI has deployed 30 permanent GPS stations across the country to monitor tectonic plate movements and develop a strain map to identify potential hazardous zones.
“Work is under progress and its first phase is likely to be completed very soon. We will also carry out seismic microzonation (process of sub-division of region) and active fault studies to evaluate potential geological vulnerable seismic sites,” Dr Som added.
Northeastern states frequently witness mild to moderate earthquakes. Seismologists consider this mountainous region as the sixth major earthquake-prone belt in the world.
Earthquakes measuring 4.2 and 5.5 on the Richter scale have jolted two districts of Mizoram alone more than 100 times in the past three months.
Experts fear this might just be a prelude to a major disaster in the region.
