Aniruddha Sengupta
Indian Institute of Technology Kharagpur, India
Title: Selection of ground motions for the Dynamic analyses of slopes in Sikkim
Biography
Biography: Aniruddha Sengupta
Abstract
Recently, an Indo-Norway collaborative study has been launched to look into the possibility of earthquake induced landslides along two strategic roadways: Gangtok to Changu Lake and Gangtok to Lachung within the Indian state of Sikkim. The state of Sikkim in India and its adjoining region are known to be the part of ‘Alpine-Himalayan global seismic belt’, a seismically very active area of the world. This region has already experienced four great earthquakes of magnitude higher than Mw=8.0 in 1897, 1905, 1934 and 1950, apart from several other large earthquakes in the densely populated region like 1905, Mw=7.5, Kangra earthquake, 2005, Mw=7.6, Kashmir earthquake, 2015, Mw=7.8 and Mw=7.3, Nepal earthquakes. The occurrence of earthquakes in the area is mainly due to the tectonic activity along well-known faults in the Himalayas, namely, Main Boundary Thrust (MBT) and Main Central Thrust (MCT). In addition to these, the prominent tectonic features in Sikkim and nearby areas are the two near parallel, NNW–SSE trending Tista and Gangtok lineaments, the WNW–ESE trending Goalpara lineament and the SW–NE trending Kanchenjunga lineament. The selection of ground motions with known probability of occurrence is an important input for the dynamic analyses of the existing slopes along the above two roadways. Thus, a probabilistic seismic hazard analysis of the areas within Sikkim is performed using the updated earthquake catalog, modified seismic sources (area source) and next-generation attenuation models. A commercially available software ‘EZ-FRISK’ is utilized to generate the total hazard curve (expressed as the annual probability of exceedance versus Peak Ground Acceleration (PGA)) and Uniform Hazard Spectra (UHS) at bedrock level. The values of peak ground accelerations and spectral acceleration for the two roadways within Sikkim for a return periods of 2474.9 years, 475 years and 97.9 years are obtained.