Rapid seismic hazard assessment of the Sabarmati River basin in Gujarat State, Western India using GIS techniques

The Sabarmati River basin, Gujarat State, western India is one of the major river basins of Gujarat State, playing host to major cities such as Ahmedabad and Gandhinagar, both of which are important economic and political capitals of Gujarat State. In the study reported here, we collected available information on the Sabarmati River basin, Gujarat State in terms of geology, tectonics, seismicity, and shear-wave velocity and assimilated and integrated this information into a geographical information system (GIS) platform to generate a rapid first-order seismic hazard map of the area. The integration of different criteria, such as peak ground acceleration, amplification factor, geology and geomorphology, liquefaction, and seismotectonics critical to seismic hazard, was performed following pair-wise comparison using the analytical hierarchy process, wherein each thematic map was assigned a weight on a 1 to 5 scale depending on its contribution to the seismic hazard. Seismic hazard was evaluated using a numerical rating scheme with the help of the GIS. Analysis of the generated map revealed that the seismic hazard is highest in the southeastern part of the area, moderate in the central part, and lowest in the northeastern part comprising the Aravalli Range. The seismic hazard map also shows that almost 40% of the study area, namely that comprising basins of the Sabarmati River and its tributaries, is prone to high seismic hazard. Our results show that it is possible to generate a macro-level seismic hazard map by integrating available information and that this map is a useful tool for urban planners and helps in zeroing in on the areas where seismic microzonation or site-specific studies are required.