SEISMOLOGY AND GEOLOGY ›› 2025, Vol. 47 ›› Issue (3): 689-706.DOI: 10.3969/j.issn.0253-4967.2025.03.20250034

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LATE QUATERNARY THROW RATE OF THE SEISMOGENIC FAULT(DENGMECUO FAULT)OF THE 2025 MS6.8 DINGRI EARTHQUAKE IN SHIGATSE

GAO Yang1,2)(), WU Zhong-hai2,3),*(), HAN Shuai2,3), TIAN Ting-ting2,3)   

  1. 1)School of History and Geography, Minnan Normal University, Zhangzhou 363000, China
    2)Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
    3)Key Laboratory of Active Tectonics and Geological Safety, Ministry of Natural Resources, Beijing 100081, China
  • Received:2025-01-25 Revised:2025-02-05 Online:2025-06-20 Published:2025-08-13

2025年定日MS6.8地震发震断层(登么错断裂)晚第四纪垂直滑动速率

高扬1,2)(), 吴中海2,3),*(), 韩帅2,3), 田婷婷2,3)   

  1. 1)闽南师范大学历史地理学院, 漳州 363000
    2)中国地质科学院地质力学研究所, 北京 100081
    3)自然资源部活动构造与地质安全重点实验室, 北京 100081
  • 通讯作者: *吴中海, 男, 1974年生, 博士, 研究员, 主要从事活动构造与古地震研究, E-mail:
  • 作者简介:

    高扬, 男, 1992年生, 2024年于北京大学获构造地质学专业博士学位, 副教授, 主要研究方向为活动构造, E-mail:

  • 基金资助:
    福建省中青年教师教育科研项目(科技类)(JZ240036); 国家自然科学基金(42472287); 国家自然科学基金(42402229); 国家自然科学基金(42202259)

Abstract:

On January 7, 2025, a significant earthquake occurred in Dingri, Shigatse, China. Both the China Earthquake Networks Center and the USGS provide focal mechanism solutions indicating that the earthquake was a normal fault event. The epicenter was located in the Dengme Cograben, part of the southern segment of the Dinggye-Xainza rift, with the seismogenic fault identified as the bounding normal fault of the Dengme Cograben, the Dengmecuo fault. The late Quaternary throw rate of this fault is crucial not only for regional seismic hazard assessments but also for understanding the east-west extensional deformation within the Tibetan plateau. Previous studies on the kinematics of the Dengmecuo fault report varying throw rates: (0.28±0.04)mm/a since ~56ka, (0.28±0.04)mm/a since ~50ka, and(0.09±0.03)mm/a since ~95ka. However, the observed maximum coseismic vertical displacement of ~3m during the January 2025 earthquake suggests that the maximum cumulative time for this displacement is approximately 37ka, based on the published late Quaternary throw rate. This is inconsistent with the ~5ka elapsed time since the most recent earthquake on this fault, highlighting the uncertainty in the late Quaternary throw rate and limiting our understanding of strain partitioning and seismic risk in the southern Dinggye-Xainza rift.

To resolve this uncertainty, we combine high-resolution remote sensing image interpretation with field geological and geomorphological surveys to determine the geometric distribution of the Dengmecuo fault. Two study sites were selected along the fault, each featuring clear faulted geomorphology suitable for dating. Low-altitude photogrammetry using an unmanned aerial vehicle(UAV)was combined with optically stimulated luminescence(OSL)and AMS 14C dating to refine the late Quaternary throw rate of the Dengmecuo fault and assess its seismic hazard.

Our results show that the Dengmecuo fault, which strikes NNW and dips NW or W, is approximately 58km long and can be divided into northern, central, and southern segments. The northern segment is defined by the Laangshuiku area, while the southern boundary is located at the edge of Pum Qu. In the northern study site, vertical offsets of 19.2(+3.5/-2.3)m on the T2 alluvial fan and 8.0(+0.9/-0.7)m on the T1 alluvial fan correspond to formation ages of(28.3±1.4)ka and(12.0±1.5)ka, respectively. By matching the vertical offsets with their respective formation ages, we estimate a throw rate of (0.7±0.1)mm/a. However, the throw rate for the T1 fan is uncertain, as its vertical offset is smaller than the cumulative displacement since its formation. At the southern study site, combining a vertical offset of 5.3(+0.3/-0.5)m with the formation age of the T1 terrace ((9.2±1.0)ka), we calculate a throw rate of(0.6±0.1)mm/a.

Overall, our results indicate late Quaternary throw rates of(0.7±0.1)mm/a since ~28ka and(0.6±0.1)mm/a since the Holocene. Additionally, using the relationship S=D/Rx, where S is the slip rate, D is displacement, and Rx is the recurrence interval, we estimate a slip rate of(0.5±0.1)mm/a based on the average value of the maximum displacement(2.5~3m)of 2025 Dingri MS6.8(Shigatse)earthquake as 2.75m and the interval of paleoseismic events during the Holocene as(5500±1100)a. This result is consistent with the throw rate of(0.6±0.1)mm/a since the Holocene determined from faulted geomorphic surfaces.

Finally, combining the throw rate of (0.6±0.1)mm/a since the Holocene with the ~5ka elapsed time since the most recent earthquake, we conclude that the Dengmecuo fault had accumulated 2.5~3.5m of coseismic displacement before the 2025 Dingri MS6.8 earthquake, corresponding to a magnitude of MW6.9-7.0. These parameters align with the 2025 MS6.8 earthquake, indicating that the Dengmecuo fault posed a significant seismic risk prior to the event.

Key words: 2025 Dingri MS6.8 earthquake, Late Quaternary activity, throw rate, Dengmecuo fault, Dinggye-Xainza rift

摘要:

2025年1月7日定日 MS6.8 地震的发震断层为定结-申扎裂谷南段登么错地堑的边界正断层——登么错断裂, 限定其滑动速率对于区域地震危险性评估具有重要意义。文中通过高分辨率遥感影像解译和野外地质地貌调查分析了登么错断裂的详细几何展布和活动特征, 根据断裂的几何展布特征将其划分为北、 中、 南3段, 且该断裂在晚第四纪期间活动性显著。结合小型无人机低空摄影测量、 地貌面定年和垂直位错量测量, 限定登么错断裂在距今约28ka以来的垂直滑动速率为(0.7±0.1)mm/a, 全新世以来的垂直滑动速率为(0.6±0.1)mm/a。结合前人报道的古地震研究结果所揭示的该断裂最近一次古地震事件的离逝时间(距今约5ka), 估算本次地震发生前登么错断裂已累积了最大3.0~3.5m的同震位移, 最大震级可达 MW6.9 ~7.0, 相关参数与2025年定日 MS6.8 地震基本一致, 这表明该断裂在本次地震前已经处于相对危险的状态。

关键词: 2025年定日MS6.8地震, 晚第四纪活动, 垂直滑动速率, 登么错断裂, 定结-申扎裂谷