Spatiotemporal variability of Neotectonic activity along the Southern Himalayan front: a geomorphic perspective

Abstract

The Sub-Himalaya is arguably consuming ~100% of the total Himalayan shortening since early Quaternary. We compiled geodetic shortening rates, paleoseismic events (historical earthquakes), shortening rates deduced from uplifted strath/fill terraces and shortening rates from balanced cross-sections from the north-western, central and eastern Himalayan compartments to obtain an orogen-wide perspective of Quaternary deformation. We supported the compiled data with topographic swath, longitudinal river-profile analysis and ksn plots of the existing drainage in those compartments. Review of the existing data shows a mismatch of the trend of the geodetic shortening rates with those of the millennial or longer timescales; however, Holocene and modern day-shortening rates are of same range (~14-21?mm.a-1). Quaternary shortening rates are much lower, probably due to a longer time-averaging. Except central Nepal, the other sectors show significant out-of-sequence thrusting (~50% of the total) within the Sub-Himalaya since the Holocene. Paleoseismic data show variable recurrence intervals of large earthquakes along-strike (~100-600 years) and large seismic gaps or slip-deficit sectors, which could potentially cause surface-rupture earthquakes in the future.