After Sunday’s earthquake, at least 15 aftershocks jolted the Kutch region of Gujarat in 24 hours till Monday evening.
According to senior seismologists, the aftershocks were grouped in and around the South Vagad Fault (SWF) fault that had given rise to the 2001 Kutch earthquake. They say Kutch is one of the rare “intraplate” regions in India that can generate devastating earthquakes of 7.5 magnitude.
“Intraplate regions are places away from the plate boundaries like the Himalayas or the Andamans. Though earthquakes in intraplate regions are rare, it can be devastating,” said M Ravi Kumar, director-general of the Institute of Seismological Research (ISR), which was been studying the seismic activity in Gujarat, including that of Kutch.
“The earthquake of Sunday was felt as far as Ahmedabad. As per our current estimates, the earthquake would have occurred at a depth of 20 kilometres or more. That is the main reason why it was so widely felt. After Sunday’s earthquake, we had 15 aftershocks — all less than 5 in magnitude,” he said.
The biggest of the aftershocks was the one measuring 4.6 that occurred at 12.57 pm on Monday. The epicentre lay 15 kilometre north-northeast of Bhachau in Kutch district. The second aftershock of 4.1 intensity struck six kilometres north-northwest of Bhachau at 3.56 pm.
While 9 aftershocks were felt on Monday, the rest hit the region late Sunday night. “It is the Vagad fault that is causing these earthquakes. We feel the same source was responsible for the Kutch earthquake in 2001,” Kumar said adding that the earthquake that occurred on Sunday was in close proximity to the epicentre of the Kutch earthquake.
ISR has laid a network of 60 seismographs of which 35-odd are spread out in Kutch district. About 45 of them are connected through VSAT and transmit real-time data about the seismic activity to ISR at Gandhinagar. “Most of the seismic activity is in Kutch and so we have the densest network in Kutch,” he said.
Seismic zones also exist in other parts of Gujarat like the Saurashtra region and the northern portion of the Gulf of Khambhat. “But the intensity of the tremors in other places is not as strong as those in Kutch,” the official added.
Gujarat has witnessed three major earthquakes in the past with the most devastating being the one in 2001, another in Anjar in 1956 and the third in 1918 in the Rann of Kutch. The January 26, 2001 Bhuj earthquake, which was of 7.7 magnitude, reportedly killed over 20,000 people and left over 1.5 lakh others injured.