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Abstract

Segmentation of the Indian lithosphere along the seismically active Himalayan collision belt, suggested by seismological and GPS studies, and analysis of topography and Bouguer gravity anomaly data, is one of the significant parameters to assess the maximum rupture area and hence the seismic energy release potential. These studies, confined to the Himalaya-Tibet region, linked major segmentation boundaries to pre-existing tectonic fabric of the Indian plate. We have studied this problem from the perspective of lithospheric flexural properties in the Himalaya-Ganga foreland basin system for possible segmentation. For this purpose, we have used the relationship between the foreland basin width (WFB) and the segment length between the Main Frontal Thrust and the Man Central Thrust (δFC) as a proxy to test possible correlation between these two parameters along the arc. The results suggest a major segmentation boundary along the Indo-Nepal border in addition to other previously discussed segmentations coinciding with major transverse ridges in the Ganga Basin. This segmentation boundary coincides with the Great Boundary Fault separating the Aravalli-Delhi mobile belt (ADMB) from the Vindhyan Basin further south. Further, we have analyzed a geomorphic index, normalized channel steepness (ksn), along the arc using the ALOS elevation dataset to test whether there is any relation between the ksn and the segmentation boundaries. Our results bring out spatial variability in the ksn along the arc and support the above segmentation. We infer a role of this segmentation boundary in limiting westward propagation of the rupture front of the 1505 paleo-seismic event.