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

Peng Guo,Jiani Li,Zhujun Han,Shaopeng Dong,Fan Gao

doi:10.3390/rs13102019

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.

Highlights

Offset landforms along a fault, such as a stream channel, river terrace, alluvial fan, or glacial moraine, can be used to identify and measure single-event and multi-event cumulative offsets of the fault, reconstruct its slip distribution and kinematics, and provide important information for understanding the seismic recurrence behavior of a fault on the magnitude scale and assessing its seismic hazards (e.g., [1,2,3,4])
Offset landforms are often hidden by vegetation in areas with high vegetation coverage, which makes it difficult to identify offsets, analyze offset geomorphic evolution processes, and understand the slip behavior of faults using high-resolution optical images, field investigations, and UAV-based photogrammetry
The inflections of the stream risers are likely to have formed due to multiple fault branches, stream hydrology events like floods, or the interaction between the faulting offset and fluvial erosion

Summary

Introduction

Offset landforms along a fault, such as a stream channel, river terrace, alluvial fan, or glacial moraine, can be used to identify and measure single-event and multi-event cumulative offsets of the fault, reconstruct its slip distribution and kinematics, and provide important information for understanding the seismic recurrence behavior of a fault on the magnitude scale and assessing its seismic hazards (e.g., [1,2,3,4]). The landform response to a fault offset and its evolution through space has been studied more frequently [5,6,7,8], the seismic recurrence of a fault from the landforms on a time scale remains poorly understood when there are no chronological data. The temporal slip pattern of a fault needs to be understood by further studying the timing of the paleoseismic events revealed by sedimentary deformation strata and chronological data (e.g., [9,10,11,12]). Offset landforms are often hidden by vegetation in areas with high vegetation coverage, which makes it difficult to identify offsets, analyze offset geomorphic evolution processes, and understand the slip behavior of faults using high-resolution optical images, field investigations, and UAV-based photogrammetry. The “bare earth” ground surface can be imaged using lidar by omitting points that are reflected off vegetation [4,16,17]

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Conclusion