SURFACE PROCESS AND FLUVIAL LANDFORM RESPONSE TO THE MS 8.0 WENCHUAN EARTHQUAKE, LONGMEN SHAN, CHINA

Abstract

The MS 8.0 Wenchuan earthquake of May 12, 2008, in the Longmen Shan mountain range area in China, led to two roughly parallel NE-trending thrust and strike-slip surface ruptures of the Beichuan, Pengguan, and the Xiaoyudong faults. Coseismic deformation changed the topographical gradient and produced massive landslides and debris flows, causing a corresponding response of the fluvial landforms. In this paper, based on data regarding the surface ruptures and changes to the topography and drainage resulting from the earthquake, the influence of the thrusting and strike-slipping on fluvial landforms and drainage are integrated and analyzed. The results are shown for the following five main aspects: (1) the strike-slipping driven by the earthquake caused the formation of new tectonic diversion points of river channels; (2) the thrusting driven by the earthquake caused the formation of new tectonic slope-break points in the river channel; (3) the strikes of the faults activated by the earthquake controlled the river channel direction; (4) the uplifting driven by the earthquake led to changes of riverbed gradient profiles and their base levels; and (5) exceptionally heavy rainfall after the earthquake initiated landslides, debris flows and floods, and will continue to be a hazard for several decades to come.