Late quaternary deformation and palaeoseismicity: Insight into geomorphotectonic evolution of Kachchh, western Indian Subcontinent

Abstract

Kachchh in western Indian Shield, according to the Bureau of Indian Standard (IS:1893:2002), falls in Seismic Zone V. This is intriguing considering that the region is far away from active Plate margin. Apart from the recent incidences of earthquakes, there are several pre-historic/archaeological records of earthquakes in the region. Beyond these, the geological evidence of earth-movements (causing earthquakes) is provided by the occurrence of several 'active' faults, which are considered geological markers of palaeoseismicity. There are records of innumerable incidences of faulting in the region in not so distant geological past. Study of fault features especially the scarp faces marking abrupt change in physical relief proves that the different levels of topography in the entire terrain are fault-bound features. Studies also confirm that the topographic difference between the high and 'sunken' features have formed due to uplift and relative down-sagging during the geomorphotectonic evolution of the terrain. Features that make the region unique are: (i) restriction of fault-related deformation zone to a narrow strip between the southern margin of Thar Desert and the south coast line of the Kachchh Peninsula; (ii) overall sub-horizontality of bedding and other topographic and planation surfaces over the entire region; (iii) evidence of fault-controlled geomorphology indicating vertical movement along fault planes; (iv) evidence constraining the time of geomorphological evolution of the terrain only during the Late Quaternary, making it the youngest neotectonically evolved terrain in the Precambrian Indian Shield.