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The intraplate Kachchh Rift basin has been hit by several devastating earthquakes in the historic past including the 1819 Allah Bund Earthquake and the 2001 Bhuj earthquake. The source region of these earthquakes, within the basin have been studied by several workers in the last two decades to understand their potential for earthquake recurrence. However, very little information is available on the palaeoseismic and geomorphic characterization of Kachchh Mainland Fault (KMF). Therefore, in the present study, six trenches were excavated across the KMF, between Lakhpat and Nirona to understand ground deformation pattern and timing of the historic earthquakes. Based on geomorphic and palaeoseismic investigations, five palaeoearthquakes of Early to Late Holocene have been identified between 10,000–890 yrs. Apart from the Holocene, an earthquake of Late Quaternary period was also identified, which possibly occurred around 19,800 yrs BP. Fault related parameters were analyzed to understand the geometry of the active fault scarp along KMF. The results of the analyzed fault geometric parameters show that the vertical displacement along the KMF is higher than the horizontal displacement. The slip rate of the KMF from the western portion to the middle portion decreases from 0.08 to 0.04 mm/yr, and increases towards east from 0.22 mm/yr to 0.36 mm/yr. As the Kachchh district of the Gujarat state is rapidly developing in terms of infrastructural development, the outcome of this research might provide significant inputs for micro zonation studies and also in the evaluation of the seismic hazard in the Kachchh region. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]