Geomorphological evidence for superimposed deformation in the southern Sichuan Basin, SW China: Implications for seismic hazards

Abstract

The 2019 M_w 5.8 Changning and 2021 M_w 5.4 Luxian earthquakes have highlighted the southern Sichuan Basin as an emerging focal area for seismic hazard research, following the significant 2008 M_w 7.9 Wenchuan and 2013 M_w 6.6 Lushan earthquakes along the Longmen Shan thrust belt. However, traditional field surveys that rely heavily on active tectonic landforms encounter considerable challenges due to the extensive exposure of pre-Cenozoic strata. In this study, we evaluate the tectonic activity of two NW-tending faults through DEM-based morphotectonic analyses. Our findings indicate that the landscape topography along the Baishuxi Fault, a principal basin-boundary fault, exhibits significant variations in geomorphic indices and topographic metrics, which may reflect a complex subsurface structural style. The presence of numerous knickpoints at various elevation levels suggests ongoing landscape adjustments in response to tectonic forces. Additionally, several knickpoints observed on river long-profiles across the Maoqiao Fault further northeast indicate basinward propagation of tectonic deformation, suggesting superimposed deformation within the southern Sichuan Basin. We recommend that future studies conduct a thorough evaluation of the seismic hazards associated with the NW-trending Baishuxi and Maoqiao faults, as well as their intersection with the NE-trending Huayinshan fault.