SURFACE DEFORMATION CHARACTERISTICS AND CAUSES OF THE DENGMECUO SEGMENT IN THE XIZANG DINGRI MS6.8 EARTHQUAKE

doi:10.3969/j.issn.0253-4967.2025.01.006

Abstract

Abstract:

On January 7, 2025, an M_S6.8 earthquake struck Dingri, Xizang, China. According to the focal mechanism solution provided by the USGS, this event was characterized as a normal faulting earthquake. The earthquake occurred in the southern segment of the Shenzha-Dingjie Rift system, which is located on the Qinghai-Tibet Plateau. This rift system is one of the seven major rift systems in the southern part of the Tibetan plateau and is a significant controlling structure for shallow-source seismic activity within the region. Moderate to major earthquakes in the study area are primarily distributed along these rift systems. Notably, the Yadong-Gulu Rift system experienced an M8.0 earthquake in 1411 near the southern part of Dangxiong.

The seismogenic fault of the earthquake is the Dengmecuo fault, which produced a 26-km-long surface rupture and deformation zone. The Dengmecuo fault is a branch of the southern segment of the Shenzha-Dingjie fault zone and is a Holocene active fault that controls the eastern boundary of the Dengmecuo Basin. The characteristics of the surface deformation zone in this earthquake differ between its northern and southern segments. The northern segment's surface rupture is primarily characterized by normal faulting, with a vertical co-seismic displacement of 2-3 meters. In contrast, the southern segment(the Dengmecuo segment)is mainly distributed on the eastern side of Dengmecuo Lake, with a width exceeding a hundred meters. The deformation characteristics of this segment are complex, exhibiting both extensional and compressional deformations. The extensional deformation zones in the southern segment, which align with the NNE-trending fault scarp, likely represent the tectonically seismogenic surface rupture zone of this earthquake. The compressive deformation zones, however, are believed to have formed as a result of the extensional deformation during the earthquake. These zones are influenced by seismic motion, local terrain, sedimentary characteristics, and climatic conditions and are not directly related to the fault's activity during the earthquake.

The differences in the characteristics of the northern and southern segments of the surface deformation zone highlight the complexity of the geometric structure and motion properties of the Dengmecuo fault. Moreover, the main surface deformation zone in the southern section does not align with the surface traces of the Dengmecuo fault, suggesting that the fault may be gradually developing inward into the basin.

Key words: the Xizang Dingri M_S6.8 earthquake, Dengmecuo Fault, Surface deformation zone, Active rift system

摘要：

2025年西藏定日6.8级地震发生在申扎-定结裂谷系南段, 其发震断裂为登么错断裂, 并形成长约26km的地震地表破裂带和形变带。其中, 北段的破裂带主要呈正断性质, 垂直同震位错量达2~3m; 南段(登么错段)的地表变形带主要分布于登么错湖东侧, 宽达上百米, 且变形性质复杂, 既有拉张变形, 又有挤压变形。在南段的拉张变形带中, 与NNE向断层陡坎展布一致的变形带, 可能是具有构造意义的地震地表破裂带。而挤压变形带应是地震中因拉张变形作用影响形成的次生地表变形带, 与地震震动、场地地形地貌、沉积特征和气候条件有关, 与发震断裂的活动无直接关系。

关键词: 西藏定日6.8级地震, 登么错断裂, 地表变形带, 活动裂谷系

LIANG Ming-jian, DONG Yun-xi, ZUO Hong, DAI You-lin, XIAO Ben-fu, LIAO Cheng, TAN Ling, WANG Yu-wei, LI Xiang, TANG Cai-cheng, ZHANG Wei, ZHANG Hui-ping, MENG Ling-yuan, SU Jin-rong, WU Wei-wei, LI Chuan-you, YAN Mei. SURFACE DEFORMATION CHARACTERISTICS AND CAUSES OF THE DENGMECUO SEGMENT IN THE XIZANG DINGRI M_S6.8 EARTHQUAKE[J]. SEISMOLOGY AND GEOLOGY, 2025, 47(1): 80-89.

梁明剑, 董芸希, 左洪, 代友林, 肖本夫, 廖程, 谭凌, 王余伟, 李响, 汤才成, 张威, 张会平, 孟令媛, 苏金蓉, 吴微微, 李传友, 严媚. 2025年西藏定日6.8级地震登么错段地表变形特征及其成因[J]. 地震地质, 2025, 47(1): 80-89.

Figures/Tables 6

Fig. 1 The map showing distribution of major faults and destructive earthquakes in the study region.

Fig. 2 The map showing the Dingri earthquake and its aftershock sequence, as well as distribution of the seismogenic fault and southern surface deformation zones.

Fig. 3 The characteristics of surface tensile deformation zone of the Dengmecuo segment(northern section).

Fig. 4 The characteristics of surface tensile deformation zone of the Dengmecuo segment(southern section).

Fig. 5 The characteristics of surface compressional deformation zone of the Dengmecuo segment(northern section).

Fig. 6 The characteristics of surface compressional deformation zone of the Dengmecuo segment(southern section).

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