New Constraints on Slip Behavior of the Jianshui Strike-Slip Fault from Faulted Stream Channel Risers and Airborne Lidar Data, SE Tibetan Plateau, China

Abstract

The temporal slip behavior of a fault from displaced landforms when there are no chronological data remains poorly understood. The southern segment of the Xiaojiang fault zone (XJFZ) plays an important role in accommodating the lateral extrusion of the SE Tibetan plateau. However, there are few reports on the evolution of the offset landforms and slip behavior of the fault due to the dense vegetation in the region. Here, offset landforms along the Jianshui fault (JSF) in the southern segment of the XJFZ are systematically interpreted and measured using high-resolution satellite imagery, field investigations, and airborne lidar. The risers on the right banks of three stream channels feature similar left-lateral offset characteristics near the town of Dongshanzhai. The left-lateral offsets consist of multiple inflections produced by seismic events, and the offset of each event is similar. These inflections are distributed downstream in a stair-stepped manner. The newly formed inflections are located close to the fault, and the earlier formed ones are eroded by flowing water and migrate downstream. The difference between the amount of downstream erosion of two adjacent inflections varies. Assuming the stream’s long-term erosion rate remains steady, the estimated time intervals between seismic events are different. Combined with the cumulative offset probability density calculation for 92 offsets, the JSF is considered to show a nonperiodic characteristic earthquake recurrence pattern. We also propose a multistage offset evolution model of the stream channel riser. This provides a new way to analyze the seismic recurrence pattern of the fault over a relative time scale.