Active tectonics evaluation from geomorphic indices for the central and the southern Longmenshan range on the Eastern Tibetan Plateau, China

Abstract

We applied the geomorphic indices (hypsometry and stream length gradient) to evaluate the differential uplift of the central and southern Longmenshan, a mountain range characterized by rapid erosion, strong tectonic uplift, and devastating seismic hazards. The results of the geomorphic analysis indicate that the Beichuan-Yingxiu fault and the Shuangshi-Dachuan fault act as major tectonic boundaries separating areas experiencing rapid uplift from slow uplift. The results of the geomorphic analysis also suggest that the Beichuan-Yingxiu fault is the most active fault with the largest relative uplift rates compared to the rest of the faults in the Longmenshan fault system. We compared reflected relative uplift rates based on the hypsometry and stream length gradient indices with geological/geodetic absolute rates. Along-strike and across-strike variations in the hypsometry and stream length gradient correlate with the spatial patterns derived from the apatite fission track exhumation rates, the leveling-derived uplift rate, and coseismic vertical displacements during the 2008 Wenchuan earthquake. These data defined multiple fault relationships in a complex thrust zone and provided geomorphic evidence to evaluate the potential seismic hazards of the southern Longmenshan range.GAO ET AL.

Late Miocene hinterland crustal shortening in the Longmen Shan thrust belt, the eastern margin of the Tibetan Plateau

“…The Wenchuan earthquake and aftershocks ruptured the Yingxiu-Beichuan and Guanxian-Anxian faults [e.g., Liu-Zeng et al, 2009;Xu et al, 2009;Ran et al, 2010;Zhang et al, 2010]. However, as the Wenchuan-Maoxian fault on the hinterland side was not activated by the earthquake [e.g., Liu-Zeng et al, 2009;Xu et al, 2009;Ran et al, 2010;Zhang et al, 2010], it has led to a major controversy as to whether the hinterland fault is active or not [Ma et al, 2005;Li et al, 2006;Chen et al, 2007;Zhang et al, 2013;Gao et al, 2016;Wang et al, 2017].…”

Topographic Loads Modified by Fluvial Incision Impact Fault Activity in the Longmenshan Thrust Belt, Eastern Margin of the Tibetan Plateau

“…Zhang et al, 2010). Previous studies also highlighted the relationships between the topography and fault activity by lateral comparison between the northern, central, and southern segments of the LTB (Gao et al, 2016;Sun et al, 2016;H. Zhang et al, 2011; Figure 1 ).…”

“…High relief, active thrust faults, and thickened, partially molten lower crust of the LTB demonstrate the ongoing contractional forces within the interior of the Earth in this region (e.g., Lu et al, ; Z. Zhang et al, ). Previous studies also highlighted the relationships between the topography and fault activity by lateral comparison between the northern, central, and southern segments of the LTB (Gao et al, ; Sun et al, ; H. Zhang et al, ; Figure ). However, the chicken‐or‐egg debate still holds due to the lack of a control group in these studies, because both the landscape and total shortening strains vary, sometimes significantly, among the segments of LTB, which weakens the argument for or against either mechanism (Godard et al, , ; Tan, Xu, Lee, et al, ; Tan, Xu, & Lu, ; E. Wang et al, ).…”

Tectonics controls on fluvial landscapes and drainage development in the westernmost part of Switzerland: Insights from DEM-derived geomorphic indices

“…S.2). The SL index has been widely adopted in different geodynamic settings Delcaillau et al, 2011;El Hamdouni et al, 2007;Figueiredo et al, 2018;Font et al, 2010;Gao et al, 2016;García-Tortosa et al, 2007;McKeown et al, 1988;Merritts and Vincent, 1989;Troiani et al, 2014) because (i) it is highly sensitive to changes in channel slope that mainly related to the presence of tectonic and/or lithological controls on the basin configuration Hack, 1973;Pedrera et al, 2009;Pérez-Peña et al, 2008b;Troiani and Seta, 2008); and (ii) the SL values can be statistically filtered to remove those values that mainly characterize each lithology unit from the whole dataset (Troiani et al, 2014;Troiani et al, 2017). In light of the above-mentioned advantages, several longitudinal profiles based on the SL index were constructed to identify any significant anomaly in the study area.…”

“…In other words, the landscapes contain important archival information of the rates and spatial distribution of deformation and erosion (Armitage et al, 2011;Kirby and Whipple, 2012). Quantitative analysis of such landscapes by using geomorphic indices can therefore provide valuable information about the genetic link between tectonic and erosion processes, which is an issue of modern tectonic geomorphology (Mayer, 1986), and help recognize late Quaternary tectonic movement (Brookfield, 1998;Delcaillau, 2001;El Hamdouni et al, 2007;Gao et al, 2016;Harvey et al, 2015;Hoke et al, 2007;Jackson et al, 1998;Keller and Pinter, 2002;Vojtko et al, 2011).…”