DISCUSSION ON COSEISMIC SURFACE RUPTURE LENGTH OF THE 2021 MW7.4 MADOI EARTHQUAKE, QINGHAI, CHINA

doi:10.3969/j.issn.0253-4967.2022.02.016

SEISMOLOGY AND GEOLOGY ›› 2022, Vol. 44 ›› Issue (2): 541-559.DOI: 10.3969/j.issn.0253-4967.2022.02.016

• Focus: Mechanical understanding of the surface ruptures of the 2021 Madoi earthquake • Previous Articles

DISCUSSION ON COSEISMIC SURFACE RUPTURE LENGTH OF THE 2021 M_W7.4 MADOI EARTHQUAKE, QINGHAI, CHINA

YAO Wen-qian¹⁾(), WANG Zi-jun¹⁾, LIU-ZENG Jing¹^,²⁾^,^*(), LIU Xiao-li³⁾, HAN Long-fei¹⁾, SHAO Yan-xiu¹⁾, WANG Wen-xin¹⁾, XU Jing⁴⁾, QIN Ke-xin¹⁾, GAO Yun-peng¹⁾, WANG Yan¹⁾, LI Jin-yang¹⁾, ZENG Xian-yang²⁾

1) Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China
2) State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
3) Institute of Seismology, China Earthquake Administration, Wuhan 430071, China
4) The Second Monitoring and Application Center, China Earthquake Administration, Xi'an 710054, China

Received:2022-01-25 Revised:2022-03-01 Online:2022-04-20 Published:2022-06-14
Contact: LIU-ZENG Jing

2021年青海玛多M_W7.4地震同震地表破裂长度的讨论

姚文倩¹⁾(), 王子君¹⁾, 刘静¹^,²⁾^,^*(), 刘小利³⁾, 韩龙飞¹⁾, 邵延秀¹⁾, 王文鑫¹⁾, 徐晶⁴⁾, 秦可心¹⁾, 高云鹏¹⁾, 王焱¹⁾, 李金阳¹⁾, 曾宪阳²⁾

1)天津大学, 地球系统科学学院, 表层地球系统科学研究院, 天津 300072
2)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
3)中国地震局地震研究所, 武汉 430064
4)中国地震局第二监测中心, 西安 710054

通讯作者: 刘静
作者简介:姚文倩, 女, 1985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及地震地质, E-mail: wenqian_08@163.com。
基金资助:
国家重点研发计划项目(2021YFC3000605-04);国家自然科学基金(U1839203);国家自然科学基金(42011540385);国家自然科学基金(42104061);地震动力学国家重点实验室开放基金(LED2020B03);中国地震局地震科技星火计划项目(XH22003C)

Abstract

Abstract:

Coseismic surface rupture length is one of the critical parameters for estimating the moment magnitude based on the empirical relationships and later used in assessing the potential seismic risk of a region. On 22 May 2021, the M_W7.4 Madoi earthquake occurred in the northeastern part of the Tibetan plateau(Madoi County in Qinghai Province, China)and ruptured the poorly known Jiangcuo Fault along the extension line of the southeastern branch of the Kunlun Fault. We began our data acquisition using aerial photogrammetry by UAV three days after the earthquake. Between 24 May and 15 June 2021, more than 40000 high-resolution low-altitude aerial photos were acquired covering a total length of 180km along the surface rupture. Based on detailed field investigations, combined with a fine interpretation of sUAV-derived orthophotos and high-resolution DEMs, we determined a total length of~158km of the coseismic surface rupture extending to the eastern end at 99.270°E, which is basically consistent with the position given by previous geophysical methods. Although the extending segment is located beyond the end of the continuous surface rupture trace near Xuema Township, it should be included in the calculation of the length of the surface rupture as part of the tectonic surface rupture. The surface rupture is segmented into four sections, named from west to east: the Eling Lake, Yematan, Yellow River, Jiangcuo branch sections. Additionally, to the east of Dongcaoa’long Lake, we mapped semi-circular arc-shaped continuous tension-shear fractures in the dune area with a short gap(~3km)connecting to the east of the Jiangcuo branch. The surface ruptures along the southeastern Youyunxiang segment also sporadically appear in several sites, locally relatively continuous, covered by the sand dune with vertical displacements of up to 30cm. After passing through the dunes, the surface rupture of the Youyunxiang segment began to spread widely, extending continuously with a strike of nearly east-west. However, it should be noted that the rupture lengths of the Youyunxiang segment and other branches are not counted in the total earthquake rupture length. By comparing the current research results, we believe that the critical factors causing the significant differences of the measured length of coseismic surface ruptures would depend on: 1)more extensive and detailed field investigations combined with a fine interpretation of high-resolution images; 2)avoidance of repeated calculation of superimposed sections on both sides of the complex geometrical area. In this study, combined with the fine interpretation of high-precision image data, many surface rupture traces in the dunes of the Youyunxiang segment were identified(verified and confirmed by field inspection)and more continuous surface rupture segments on the F1 fault, which is difficult to reach by human beings, were discovered, also highlights the important role of digital photogrammetry in the study of active tectonics. The studies of the strong historical earthquakes around the Bayan Har block show that the coseismic surface rupture length is larger than that estimated by the empirical relationships. Further research thus is highly necessary to uncover its mechanism and indicative significance.

Key words: Madoi earthquake, coseismic surface rupture length, Jiangcuo branch, high-resolution images, moment magnitude

摘要：

同震地表破裂长度是区域活动断裂最大震级估算以及区域未来地震潜力评估的重要参数之一。2021年5月22日在青海省果洛藏族自治州玛多县发生了 M_W7.4 地震, 其触发的同震地表破裂沿东昆仑断裂东南分支延伸线上的江错断裂分布。文中基于震后2次大范围的野外调查, 结合无人机航拍影像和高精度地形数据的精细解译, 明确了此次地震的同震地表破裂自西往东可划分为鄂陵湖南段、野马滩段、黄河乡段和江错分支段, 最东端的地表破裂位置位于前人研究所确定的最东端以东2km以远, 破裂全长约158km。此外, 本研究在冬草阿隆湖以东的沙丘区域内发现了呈半圆弧形连续分布的地表破裂, 而破裂在沿走向SE的优云乡段的传播过程中所经过的大面积沙丘覆盖区域也存在零星的张剪性地表破裂和断层陡坎, 且陡坎的垂向位移可达30cm。对比已有的关于同震地表破裂长度的研究结果, 分析认为本研究与其他结果之间存在差异的主要原因在于: 1)本研究所得结果基于更广泛、详实的野外调查和更大范围的高精度影像的精细解译; 2)分析过程中避免了阶区等段落几何复杂区两侧叠加段落的重复计算。结合巴颜喀拉块体周缘已有的强震震例, 均显示青藏高原地区同震地表破裂的长度较全球平均值偏大。

关键词: 玛多地震, 同震地表破裂长度, 江错分支段, 高精度影像, 震级

CLC Number:

P315.2

YAO Wen-qian, WANG Zi-jun, LIU-ZENG Jing, LIU Xiao-li, HAN Long-fei, SHAO Yan-xiu, WANG Wen-xin, XU Jing, QIN Ke-xin, GAO Yun-peng, WANG Yan, LI Jin-yang, ZENG Xian-yang. DISCUSSION ON COSEISMIC SURFACE RUPTURE LENGTH OF THE 2021 M_W7.4 MADOI EARTHQUAKE, QINGHAI, CHINA[J]. SEISMOLOGY AND GEOLOGY, 2022, 44(2): 541-559.

姚文倩, 王子君, 刘静, 刘小利, 韩龙飞, 邵延秀, 王文鑫, 徐晶, 秦可心, 高云鹏, 王焱, 李金阳, 曾宪阳. 2021年青海玛多M_W7.4地震同震地表破裂长度的讨论[J]. 地震地质, 2022, 44(2): 541-559.

Figures/Tables 11

Fig. 1 Distribution of major active faults and earthquakes of the Tibetan plateau.

Fig. 2 Map showing the UAV operation area.

Fig. 3 Segmentation of coseismic surface rupture of the Madoi MW7.4 earthquake and distribution of active faults in the study area.

Fig. 4 High-resolution DEM and mapping of the surface ruptures along the Jiangcuo section.

Fig. 5 Characteristics of the coseismic surface ruptures near the Xuema village.

Fig. 6 Sparse distribution of the coseismic surface ruptures to the east of the Xuema village produced by Madoi earthquake.

Fig. 7 Characteristics of the subtle coseismic surface ruptures to the eastern end of the Jiangcuo section.

Fig. 8 Photographs showing coseismic surface ruptures in the dune of the Youyunxiang section.

Fig. 9 Characteristics of coseismic surface ruptures of the Eling Lake section.

Table1 Length of the coseismic surface ruptures of the MW7.4 Madoi earthquake

序号	地表破裂长度/km	量测方法	来源
1	152.4	野外踏勘	潘佳伟等, 2021
2	160	野外踏勘	李智敏等, 2021
3	170	大地测量	王未来等, 2021
4	150	大地测量	赵韬等, 2021
5	180	大地测量	徐志国等, 2021
6	210	大地测量	华俊等, 2021

Fig. 10 Regressions of moment magnitude versus surface rupture length(modified based on results of Well et al.,1994).

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