Influence of fault geometry and fault interaction on strain partitioning within western Sichuan and its adjacent region

Abstract

There are several major active fault zones in the western Sichuan and its vicinity. Slip rates and seismicity vary on different fault zones. For example, slip rates on the Xianshuihe fault zone are higher than 10 mm/a. Its seismicity is also intense. Slip rates on the Longmenshan fault zone are low. However, Wenchuan Ms8.0 earthquake occurred on this fault zone in 2008. Here we study the impact of fault geometry on strain partitioning in the western Sichuan region using a three-dimensional viscoelastoplastic model. We conclude that the slip partitioning on the Xianshuihe-Xiaojiang fault presents as segmented, and it is related to fault geometry and fault structure. Slip rate is high on fault segment with simple geometry and structure, and vice versa. Strain rate outside the fault is localized around the fault segment with complex geometry and fault structure. Strain partitioning on the central section of the Xianshuihe-Xiaojiang fault zone is influenced by the interaction between the Anninghe-Zemuhe fault and the Daliangshan fault zone. Striking of the Longmenshan fault zone is nearly orthogonal to the direction of eastward extrusion in the Tibetan Plateau. It leads to low slip rate on the fault zone.