A Kutch-like quake shook Vadnagar a 1,000 years ago

Ahmedabad: It was a jolt from the past – literally – for researchers working on archaeological sites at Vadnagar when they discovered that a major earthquake, with an estimated moment magnitude of around 7, had rocked the north Gujarat region around 9th-10th CE. This makes its intensity close to the 7.6 magnitude temblor that wreaked havoc in Gujarat – specifically Kutch region –on Jan 26, 2001, claiming thousands of lives.
What's just as important, the researchers said the quake experienced around a 1,000 years ago made those living in the ancient town – having a history of more than 2,500 uninterrupted years of occupation – prepare for such cataclysmic events in the future. This is proven by excavated structures there being one of the earliest documented earthquake-resistant ones in Asia, they claimed.
The study also indicated that the ‘Vadnagar Fault' resulted in re-orientation of several rivers in the region, including Rupen. While the study's purview did not include the north Gujarat riverine system that includes Saraswati, the period of the event may coincide with major change in flow of rivers, the experts said.
The findings, a result of work stretching over a decade, were recently published in a study, ‘An archaeo-seismological investigation of the footprints of human resilience to seismic shaking from the alluvial plains of Gujarat, Western India,' in Elsevier journal Geomorphology.
The researchers -- Aashna Tandon, Siddharth Prizomwala, Tarun Solanki, Abhijeet Ambekar, Rakesh Nikam, Pradeep Srivastava and Sumer Chopra -- are from Institute of Seismological Research (ISR) Gandhinagar, ASI and IIT Roorkee.
Aashna Tandon, senior research fellow with ISR, said thorough studies helped calculate the moment magnitude of the event that created a rupture, which has been identified as ‘Vadnagar Fault.'
"While the earthquake in Kutch in 2001 took place in seismic zone V, which is an earthquake-prone area, a similar magnitude earthquake occurring in seismic zones III and IV that include Mehsana and Vadnagar is an unusual event. We could find its signs in several of the structures where the displacement of layers of brick and mason work and the land showed the direction of distress," said Prizomwala.
Ambekar, who oversaw the excavation work, said that from an archaeological perspective, the discovery of the earthquake had added a new chapter to the town's history.
Talking about the people's response to the event, he said, "We find evidence of timber bonding structures in masonry walls due to absence of rows of bricks, indicating possible presence of timber/wood as shock absorbers for any seismic event. Such innovations have also been found in some western Asian countries, but this is one of the earliest evidence of anti-seismic architecture," he said.