Seismic Safety of Buildings on Indian Hill Slopes—A Review

The entire Himalayan belt extending from Shimla to Gangtok and the North-East Indian region lies in high seismic risk zones. In the recent past, this region has experienced several devastating earthquakes, which have signalled the high vulnerability of the structures, especially housing stocks. Population outbursts and rapid urbanisation have led to unplanned growth and rapid coming up of houses and buildings. A similar trend can be seen in some of the habitable areas along hill slopes as well. Lack of flat land availability in hilly areas often results in the construction of buildings on sloping grounds causing the structural foundation to follow the natural slope. The dynamic characteristics of such buildings are significantly different from the ones resting on flat topography due to their irregularity in both horizontal and vertical directions. Poor implementation of building bye-laws, non-engineered construction, the dearth of proper geotechnical investigation, low maintenance of older buildings and frequent use of inferior construction materials are unfortunate challenges for seismic safety. Some of the significant observations of past studies to assess the seismic safety and vulnerability of buildings on Indian hill slopes is elaborated herein. This study highlights and summarises the challenges and undesirable construction practices that put the buildings on hill slopes at high seismic risk.