Geomorphic expressions of active tectonics across the Indo-Burma Range
Patcharaporn Maneerat, Roland Bürgmann
Abstract
The Indo-Burma Range (IBR) is an accretionary complex associated with the oblique subduction zone between India and the Burma microplate. It remains an outstanding question whether the ongoing plate-boundary deformation involves active subduction of the Indian plate. To study the tectonics in this region, we investigate drainage divide stability and the topographic expression of active tectonics across the IBR. We extract elevation data from the 30 × 30 m SRTM digital elevation model and identify streams, drainage divides and basins. We select the divide segments to construct and evaluate divide stability using the Gilbert metrics and χ values of the channel heads located on both sides of the divide portions. We calculate several geomorphic indices, including basin-scale (hypsometry and relief) and stream-scale (normalized steepness index [ksn]) measures to reveal tectonic uplift patterns. We find that most of the divide segments are static, allowing us to study the morphometry of streams and drainage as indicators of spatial variation in tectonic uplift in the context of large-scale variations of precipitation and lithology. Our morphometric results support ongoing tectonic uplift distributed across the inner belt of the IBR, and they cannot be explained by variations in precipitation or lithology. The eastern region is characterized by higher relief, hypsometry and ksn compared to the western outer belt. While the active deformation front lies far to the west, the inferred higher uplift rates in the eastern range suggest active out-of-sequence thrusts in the inner belt of the IBR that splay off from the active megathrust.