Examining the suitability of the geomorphic parameters in generating the Relative Index of Active Tectonics: an example from Himalayan Frontal Thrust, India

This work emphasizes the efficient use of geomorphic parameters to form a unified index ~ Relative Index of Active Tectonics (RIAT), which has seldom been tested in areas with broader variability in the rate of deformation. This study aims to verify whether the geomorphic parameters can be used efficiently for RIAT to assess the spatial variability in deformation along the fault. The Himalayan Frontal Thrust has been chosen for morphotectonic evaluation owing to its active interplate thrust fault setting. For this purpose, we select vertical uplift sensitive geomorphic parameters viz., Mountain front sinuosity (S_mf), Valley floor width-height ratio (V_f), and Steepness index (K_sn), as a primary tool to test the RIAT.

The result of RIAT shows the along-strike variation in response to the varying degree of deformation along the HFT. This is in fine agreement with the available long-term uplift/shortening rates and geodetic rates. Overall examination reveals RIAT being an excellent tool to assess the spatial variability in uplift rates in large tectonically active regions. However, the detailed scrutiny of individual geomorphic parameters reveals that only V_f, and the K_sn index are more responsive and go hand-in-hand with the RIAT variation. Whereas, S_mf shows no spatial variation and function as least sensitive to such an investigation. The sensitivity of these individual parameters has implications for studies with similar settings elsewhere when quantitative rates are absent.