Surface deformation of northeastern Taiwan revealed by geomorphic indices

Abstract

In northeast Taiwan, many areas are affected by various tectonic forcings. Some areas appear to have a subsidence tendency, whereas others reflect uplift activities on the surface, due to tectonic northward compressive forcing growth and decline. Owing to the presence of widespread mountain areas, limited geodetic surveys in the field have made data scarce in the study area in the past decades. The distribution of the geomorphic indices, which were calculated along the river channels, were used to analyze the activities on a regional scale in this study. The long-term landscape evolution of drainage basins can record topographic changes through the river channels. By calculating the location and drop height of knickpoint in the river longitudinal profile, as well as the spatial distribution of the normalized steepness index ($K_{\mathit{sn}}$) value, it is possible to comprehensively discuss the perturbations that were caused by possible factors in river channels. Our results from the geomorphic indices synthetically suggest that the river channel of drainage basins is mainly influenced by the perturbations such as geological structures, tectonic activity, various lithologies, potential ruptures. In the study area, tectonic forcing act on a large area from north to south, which is reflected in the long-term incision of the river into the bedrock. Moreover, the potential ruptures on the surface may also induce displacement in the local area.

Key points

The geomorphic indices reveal surface deformation on a regional scale.

The long-term perturbations caused by endogenetic process on river channels.

The landscape evolution model was generalized based on the result of the geomorphic indices.