West Ahmedabad at Greater Seismic Risk, Survey Says | Ahmedabad News

AHMEDABAD: Between June and August 15 this year, at least three low-intensity earthquakes were felt in Ahmedabad ahead of the state government’s ambitious skyscraper policy, promising to change the skyline of ‘Ahmedabad. But before this policy finds its place in the existing General Development Control Regulation (GDCR), attention should be drawn to the very recent integrated seismic hazard map for the city of Ahmedabad by the Seismological Research Institute (ISR). The GDCR was formulated after the 2001 earthquake.
The map, released in October 2019, provides details of the areas where buildings are and will be vulnerable in the event of an earthquake in Ahmedabad. He claims that areas like Jodhpur Gam, Satellite, Memnagar and Thaltej fall under the very high seismic risk area. These areas are riskier than Maninagar, Isanpur and Ghodasar.

In the western part, Sola, Gota, part of Sarkhej and Vasna are “safe” according to the ISR card. The next ones in the riskier areas are Navrangpura, Usmanpura, Keshavnagar, Bapunagar, Rakhial and Narol Chokdi, while Chandkheda and its surroundings are in safe or moderate areas.
Research suggests that the presence of sand and floodplain deposits along the Sabarmati River increases the risk. “The western part of Ahmedabad presents the highest risk. The northern and eastern parts present a moderate seismic risk, ”said the study, written by Vinay Dwivedi of ISR, Vasu Pancholi, Madan Rout, Pawan Singh, B Sairam, Sumer Chopra, former DGISR BK Rastogi and RK Dubey of IIT (ISM), Dhanbad.
“23 holes were drilled”
The detailed micro-level seismic risk assessment map for the city of Ahmedabad was produced using geotechnical methods, mainly to help urban planners and structural engineers to design buildings and other engineering structures civilians to reduce the likelihood of loss of life and property in the event of an earthquake.
The map was assembled after years of field and laboratory tests conducted on soil samples, geophysical surveys, collection of seismotectonic information to estimate the thickness of land cover, wave speed of shear, the safety factor against liquefaction and the site response in terms of the earthquake amplification factor.
The study was published in the Springer Bulletin of Engineering Geology and the Environment in October 2019. Participating researchers were from ISR and the Indian Institute of Technology, Indian School of Mines IIT (ISM) in Dhanbad. For this study, 23 boreholes were drilled at different locations in Ahmedabad and sensor-based field laboratory tests were carried out at 54 locations. Overall, the western part of Ahmedabad was at the highest risk. The northern and eastern parts presented a moderate seismic hazard.

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