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Seismic and aseismic fault slip revealed by luminescence bleaching depth profiles of the bedrock normal fault scarp

Jie Chen, Ming Luo, Jintang Qin, Jinhui Yin, Lewis A. Owen, Haoran Wang, Huili Yang, Jinfeng Liu, & Boxuan Zhang

Published August 15, 2018, SCEC Contribution #8643, 2018 SCEC Annual Meeting Poster #230

Understanding the partitioning of seismic and aseismic fault slip is critical to seismotectonics as it ultimately determines the seismic potential of faults. Recent advances in tectonic geodesy and remote sensing make it possible to develop kinematic models of the spatiotemporal evolution of slip over the seismic cycle and to determine the budget of seismic and aseismic slip in subduction zones and continental faults in past two decades (eg. Avouac, 2015; Harris, 2017). However, it is still difficult to distinguish and estimate seismic and aseismic slip in geological time scale. Bedrock fault scarps are one of the best archives of past fault slip. They are clearly associated with a particular fault, record whole slip history (Zreda and Noller, 1998). However, their reconstructions are limited because they often lack precise temporal constraint.

Recently, a new method dating for rock surfaces pioneered by Sohbati et al. (2011, 2012), is based on optically stimulated luminescence (OSL) bleaching profiles. If a rock surface continuously exposed to daylight, the luminescence resetting will penetrate deeper into the surface with time (the rock "bleaches"). Therefore, measuring the extent of bleaching in a sample can provide a measure of how long the sample has been exposed to daylight. Here, several models for luminescence bleaching depth profiles of bedrock normal fault scarps are proposed. The infra-red stimulated luminescence (IRSL) signals from rock slices exhibit increasingly deep bleaching profiles with altitude along the fault surface, which is consistent with episodic seismic or progressive aseismic fault slip. We demonstrate a case study of a bedrock normal fault surface at Langshan in north China, and show that rock luminescence bleaching profiles can be used to distinguish and estimate seismic and aseismic slip and is a promising tool for high-resolution reconstruction of fault slip, both in space and time, especially for events up to few hundreds or thousand years old.

Key Words
Seismic slip, creep, luminescence bleaching profile, bedrock normal fault scarp

Chen, J., Luo, M., Qin, J., Yin, J., Owen, L. A., Wang, H., Yang, H., Liu, J., & Zhang, B. (2018, 08). Seismic and aseismic fault slip revealed by luminescence bleaching depth profiles of the bedrock normal fault scarp. Poster Presentation at 2018 SCEC Annual Meeting.

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