Fig. 2: Simplified sketch illustrating the various processes impacting the shape of alluvial terrace tread in the Sarpang area.
a The conventional approach used by Berthet et al.12 views terraces as markers of tectonic activity associated with movement along planar fault surfaces with constant dips. The alluvial plain deformed by these faults is a flat surface over which a channelized river flow. The resulting terrace tread exhibits a smooth surface, and its geometry can be associated with the constant uplift of a rigid block. b Geological and geophysical observations indicate that more than this simple approach may be required. Alluvial deposits, even in active river beds, can vary in height by several meters, with geomorphic markers such as natural levees, point bars, banks, or pools. We propose an upgraded model to interpret the observed unevenness of terrace tread, accounting for a complex fault geometry, as suggested by lateral variations of the scarp toe or imaged by geophysical investigations and considering variations in aggradation.
