地震地质 ›› 2024, Vol. 46 ›› Issue (2): 357-370.DOI: 10.3969/j.issn.0253-4967.2024.02.007

• 研究论文 • 上一篇    下一篇

基岩断层面黏滑和蠕滑时岩石表层光释光信号模拟

罗明1,2,3,4)(), 陈杰3,4),*(), 覃金堂3,4), 尹金辉3,4), 杨会丽3,4), 刘进峰3,4), 龚志军2)   

  1. 1) 东华理工大学, 江西省数字国土重点实验室, 南昌 330013
    2) 东华理工大学, 地球科学学院, 南昌 330013
    3) 中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029
    4) 新疆帕米尔陆内俯冲国家野外科学观测研究站, 北京 100029
  • 收稿日期:2023-03-07 修回日期:2023-06-25 出版日期:2024-04-20 发布日期:2024-05-29
  • 通讯作者: *陈杰, 男, 1966年生, 研究员, 主要研究方向为新构造与活动构造、 第四纪地质及年代学, E-mail: chenjie@ies.ac.cn
  • 作者简介:

    罗明, 男, 1989年生, 2019年于中国地震局地质研究所获构造地质学博士学位, 讲师, 研究方向为活动构造与释光年代学, E-mail:

  • 基金资助:
    国家自然科学基金(42202247); 地震动力学国家重点实验室项目(LED2022B07); 国家重点研发计划项目(2022YFC3003700); 东华理工大学江西省数字国土重点实验室开放研究基金(DLLJ202209)

SIMULATION OF THE ROCK SURFACE LUMINESCENCE SIGNALS ON BEDROCK FAULT SCARPS BY STICK-SLIP AND CREEP MOVEMENTS

LUO Ming1,2,3,4)(), CHEN Jie3,4),*(), QIN Jin-tang3,4), YIN Jin-hui3,4), YANG Hui-li3,4), LIU Jin-feng3,4), GONG Zhi-jun2)   

  1. 1) Key Laboratory for Digital Land and Resources of Jiangxi Province, East China University of Technology, Nanchang 330013, China
    2) School of Earth Sciences, East China University of Technology, Nanchang 330013, China
    3) State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
    4) Xinjiang Pamir Intracontinental Subduction National Observation and Research Station, Beijing 100029, China
  • Received:2023-03-07 Revised:2023-06-25 Online:2024-04-20 Published:2024-05-29

摘要:

重建断层的黏滑(seismic slp)和蠕滑(creep)历史对于更好地了解断层活动和地震危险性评估至关重要。近年来, 利用大地测量技术研究活动断层的蠕滑和黏滑过程成为一个研究热点。然而, 在地质历史时期(如百年尺度以上), 如何判断活动断层的滑动方式(黏滑或蠕滑), 并获取其滑动速率仍然是一项挑战。文中基于近十年来发展的岩石表层光释光测年方法, 结合内蒙古狼山断裂花岗岩样品的光释光晒退参数进行理论模拟, 得到了基岩正断层发生黏滑、 蠕滑和崩积楔侵蚀等情形的光释光晒退模型。模拟结果表明, 该方法能够有效区分断层的黏滑和蠕滑, 获得相应的活动期次和位移量, 并且有潜力记录崩积楔侵蚀。文中还分析了该方法区分断层活动方式、 期次的时间分辨率和获得位移量的空间分辨率。

关键词: 基岩断层面, 黏滑, 蠕滑, 岩石表层, 光释光测年

Abstract:

The reconstruct of the stick-slip and creep histories is essential for understanding fault activities and seismic hazard assessment. Distinguishing stick-slip and creep using geodetic technology has become a hot research area in recent years, but distinguishing and estimating seismic slip and creep on geological timescales(e.g., over hundreds of years)is challenging due to the lack of historical, geodetic and remote sensing data extending back more than a few hundred years. This study uses a newly developed dating technique(rock surface optically-stimulated-luminescence(OSL)dating)combined with the OSL decay parameters of granite samples from the Langshan fault in Inner Mongolia to simulate optically stimulated OSL-depth curves and depths of half saturation of luminescence signal under various scenarios such as fault seismic slipping, creeping, and erosion of colluvial wedge. The study compares these OSL-depth profiles, especially the depths of the half saturation, under different slipping modes, and summarizes their features.

During fault seismic slip, samples at different heights along the fault scarp display a “step-like” distribution pattern at their depths of half saturation. While during creep, however, they exhibit a “slope-like” pattern. Such differences may lie in that the slope during accelerating creeping is steeper than the slope during constant-speed creeping. Correspondingly, the resolution of residual luminescence-depth profile and depth of half saturation is also higher during accelerating creeping. During intra-earthquake creep events between seismic slip occurrences on the bedrock fault scarp, the distribution of half-saturation depth in the samples includes segments resembling both “steps” and “slopes”, which indicate the seismic slip and creep activities of the fault respectively. If the samples at the base of the colluvial wedge have had a sufficiently long last exposure time, the luminescence-depth profile and half-saturation depth distribution due to the erosion of the colluvial wedge would be approximately the same as in the three-phase seismic slip scenario. This indicates that samples previously buried by the colluvial wedge may be considered within the seismic displacement. Conversely, if the last exposure time of the base samples at the base of the colluvial wedge is short, the bleaching depth of the luminescence signal of these base samples will be noticeably shallower than that of the other samples within the seismic displacement, indicating the observed erosion of the colluvial wedge in this case. Furthermore, the seismic displacement ideally should include the buried location of the colluvial wedge. Therefore, when the luminescence curves and half-saturation depth distributions fail to identify the presence of the colluvial wedge, it is acceptable to include the buried location of the colluvial wedge in the seismic displacement calculation. Conversely, the luminescence-depth curves and half-saturation depth distributions document the erosion caused by the colluvial wedge. The simulation results demonstrate that this method can effectively distinguish between fault slipping and creeping, obtain corresponding displacements, and potentially record the erosion of colluvial wedge.

This study also analyzes the temporal resolution of the method for distinguishing fault activity times and the spatial resolution for quantifying displacements. The specific situation is as follows. When exposure age of the bedrock fault scarp is within a thousand years, the rock surface OSL dating method can easily distinguish types of active slips and seismic displacements for the earthquakes with a recurrence interval of hundreds of years. When exposure age of the bedrock fault scarp is in the range of 100-101ka, the method can easily distinguish types of active slips and seismic displacements for the earthquakes with a recurrence interval exceeding a thousand years. When exposure age of the bedrock fault scarp is over ten-thousand years, the resolution of this method may be significantly reduced. The spatial resolution of seismic displacements using this method depends on interval between sampling and testing samples, typically in 10~30cm.

Key words: Bedrock normal fault scarp, stick-slip, creep, rock surface, optical stimulated luminescence dating