STUDY ON THE EFFECT OF EXCESS TOPOGRAPHY ON LANDSLIDES INDUCED BY LUDING MS6.8 EARTHQUAKE IN 2022

doi:10.3969/j.issn.0253-4967.2024.04.002

Abstract

Abstract:

Strong earthquakes in mountainous regions are prone to triggering severe geological disasters, such as landslides, collapses, and debris flows. These disasters are characterized by their wide distribution, large scale, and high frequency, making them among the most destructive secondary effects of earthquakes. In recent years, the central and eastern parts of the Qinghai-Tibet Plateau have experienced frequent strong earthquakes, leading to varying degrees of earthquake-induced landslide disasters.
Landscape evolution is significantly influenced by tectonic activities and river incising, which alter the materials of hillslopes and their topographic characteristics. Earthquakes can significantly affect the spatial distribution of co-seismic landslides, particularly in areas with excess topography. In tectonically active zones, rock uplift and river erosion gradually increase slope angles and decrease slope stability. Weathering, freeze-thaw cycles, and seismic vibrations can reduce rock strength, leading to slope erosion and landslides. Once these processes occur, the slope tends to reach a critical state of stability, which is characterized by the presence of excess topography. Landslides can rapidly reduce hillside elevations, limiting terrain relief and impacting landform evolution. Excess topography, defined as rock mass inclined at angles greater than a specified threshold, is closely related to unstable slope masses. The essence of a landslide is the disruption of slope equilibrium, often reflected in the presence of excess topography. However, the influence of excess topography on the distribution of co-seismic landslides is not well understood.
Earthquake-induced landslides occur when slopes become unstable and slide due to seismic forces. The instability arises when ground motion alters the internal friction angle and cohesion forces along rock mass defects, making them unable to resist the gravitational forces that cause sliding. The weight of the slope material plays a crucial role in this process. As a key component of landscape evolution, landslides significantly shape geomorphic forms, as indicated by the presence of excess topography. The undulating terrain of a region is the result of long-term structural and surface erosion interactions, as well as material migration and distribution. Landslide development is closely related to the local environment, particularly geomorphic conditions. Seismic landslides also play a vital role in shaping and reorganizing active orogenic belts, influencing subsequent landscape evolution.
On September 5, 2022, a M_S6.8 earthquake struck Luding county, Sichuan province, China, with the epicenter in Hailuogou Glacier Forest Park(29.59°N, 102.08°E), at a focal depth of 16km and a maximum intensity of Ⅸ degrees. The earthquake, lasting approximately 20 seconds, was strongly felt across many parts of Sichuan Province and induced numerous landslides, causing significant damage. The affected area, located at the transition between the Qinghai-Tibet Plateau and the Sichuan Basin, features a typical alpine and canyon landscape with steep terrain and river incision, providing favorable conditions for landslides. The long-term and intense tectonic activity in the eastern Qinghai-Tibet Plateau has resulted in complex topography and geomorphology, providing the material basis and external conditions for earthquake and landslide disasters.
With advancements in science and technology, the Digital Elevation Model(DEM)has become widely used in geoscience research. As DEM accuracy improves, its applications have evolved from qualitative descriptions of geomorphic morphology to semi-quantitative and quantitative analyses of various geomorphic parameters. Geomorphic parameters reveal the structural geomorphic information within topography, essential for understanding regional characteristics and evolution mechanisms. The Luding earthquake serves as a case study for analyzing the influence of topography on the distribution of co-seismic landslides.
In this study, through post-earthquake remote sensing image analysis we identified 1 485 landslides(covering approximately 14.83km²)and analyzed their spatial distribution. Field surveys revealed that most co-seismic landslides are shallow, with relatively small thicknesses, primarily located along the Dadu River. Excess topography calculations based on the ALOS 12.5m DEM and subsequent quantitative analysis of its correlation with co-seismic landslides indicate a strong relationship: with a 30° threshold, excess topography peaks are found along the Dadu River and its tributaries, coinciding with the majority of landslide occurrences. A total of 91.7% of co-seismic landslides are within areas of varying excess topography heights. However, the average height of excess topography in landslide areas(~80m)significantly exceeds landslide thicknesses, suggesting that the Luding earthquake only mobilized a small fraction of the total excess topography. The remaining excess topography may represent potential unstable slopes for future landslides. Furthermore, the spatial distribution of landslides induced by previous earthquakes, such as the Wenchuan earthquake in 2008, the Lushan earthquake in 2013, and the Ludian earthquake in 2014, shows a high degree of consistency. This underscores the importance of understanding the relationship between excess terrain and landslide distribution to enhance the accuracy of earthquake-induced landslide predictions.

Key words: 2022 M_S6.8 Luding earthquake, seismic landslide, excess topography, landslide distribution

摘要：

地貌演化受到构造活动和河流侵蚀等作用影响。作为地貌演化的重要组成部分, 滑坡对于塑造地貌形态起到了重要作用。滑坡发生的本质是坡体平衡受到破坏, 而这种不平衡现象可体现为存在过剩地形。2022年9月5日四川省泸定县 M_S6.8 地震诱发了大量山体滑坡, 为研究过剩地形对同震滑坡的空间分布提供了一个研究实例。文中基于震后遥感影像对同震滑坡进行了提取, 并依据ALOS 12.5m地形高程数据计算了震区过剩地形。此次工作共识别出1 485个滑坡(面积约为14.83km²), 这些同震滑坡多为浅层滑坡, 呈带状集中分布于大渡河两侧。同时, 过剩地形的计算结果显示其主要分布在大渡河及其支流的山谷两侧。相关性分析结果表明, 高达91.7%的同震滑坡分布在不同厚度的过剩地形分布区。为了进一步研究过剩地形和同震滑坡的空间关系, 文中对2008年汶川地震、 2013年芦山地震和2014年鲁甸地震等诱发滑坡与过剩地形的空间分布进行了分析, 结果表明二者的空间分布具有高度的一致性, 显示出过剩地形对同震滑坡空间分布的控制作用。值得注意的是, 文中计算获得的泸定地震震区过剩地形的平均高度约为80.0m, 明显大于此次地震诱发滑坡的厚度, 这意味着此次同震滑坡仅仅是移除了很少部分的过剩地形, 据此推测剩余的过剩地形分布区仍是未来潜在的滑坡易发区。

关键词: 2022年M_S6.8泸定地震, 同震滑坡, 过剩地形, 滑坡分布

QIU Heng-zhi, MA Si-yuan, CHEN Xiao-li. STUDY ON THE EFFECT OF EXCESS TOPOGRAPHY ON LANDSLIDES INDUCED BY LUDING M_S6.8 EARTHQUAKE IN 2022[J]. SEISMOLOGY AND GEOLOGY, 2024, 46(4): 783-801.

邱恒志, 马思远, 陈晓利. 2022年M_S6.8泸定地震诱发滑坡中过剩地形的影响[J]. 地震地质, 2024, 46(4): 783-801.

Figures/Tables 16

Fig. 1 Geological structure map of the study area and its adjacent region.

Fig. 2 Remote sensing image of part impacted area of Luding earthquake.

Fig. 3 Distribution map of stratigraphic chronology and landslides induced by Luding earthquake.

Table1 Characteristics of coseismic landslides at different scales

分类	滑坡面积/m²	滑坡数量	比例/%
Ⅰ	面积<2000	447	30.10
Ⅱ	2000≤面积<5000	418	28.15
Ⅲ	5000≤面积<10000	257	17.31
Ⅳ	10000≤面积<50000	320	21.54
Ⅴ	面积≥50000	43	2.90
总计		1485	100

Fig. 4 Distribution of landslides area with seismic density.

Fig. 5 Typical sites of landslides caused by the Luding earthquake.

Fig. 6 Calculation of excess topography from 1D elevation profile(revised from Blöthe et al., 2015).

Fig. 7 Map of excess topography distribution in earthquake zone.

Fig. 8 Relationships of distribution of coseismic landslide with excess topography and topographic factors.

Fig. 9 The relationship between coseismic landslides and excess topography distribution with different seismic intensities.

Fig. 10 Continuous variation of excess topography along AA' profile.

Fig. 11 Analysis of influencing factors on excess topography.

Fig. 12 Distribution of excess topography at different stratigraphic chronology.

Fig. 13 Average slope, elevation and excess topography height along AA' profile.

Fig. 14 Distribution of landslide and excess terrain induced by different earthquakes.

Table2 Statistical distribution of coseismic landslides in excess terrain induced by different earthquakes

地震	同震滑坡面积 /km²	位于过剩地形中的滑坡面积 /km²	所占面积比 /%	同震滑坡数 /个	位于过剩地形中的滑坡数 /个	所占个数比 /%
2008年汶川地震	1146.04	864.88	75.5	165025	120578	73.1
2013年芦山地震	17.16	13.76	80.2	21055	14350	68.2
2014年鲁甸地震	5.01	4.28	85.4	610	532	87.2
2022年泸定地震	14.83	13.6	91.7	1485	1383	93.1

References 37

[1]	曹鹏举, 程三友, 林海星, 等. 2021. DEM在构造地貌定量分析中的应用与展望[J]. 地质力学学报, 27(6): 949—962.
	CAO Peng-ju, CHENG San-you, LIN Hai-xing, et al. 2021. DEM in quantitative analysis of structural geomorphology: Application and prospect[J]. Journal of Geomechanics, 27(6): 949—962. (in Chinese)
[2]	邓起东, 冉勇康, 杨晓平, 等. 2007. 中国活动构造图 [CM]. 北京: 地震出版社.
	DENG Qi-dong, RAN Yong-kang, YANG Xiao-ping, et al. 2007. Active tectonic map of China [CM]. Seismological Press, Beijing. (in Chinese)
[3]	范宣梅, 王欣, 戴岚欣, 等. 2022. 2022年 M_S6.8 泸定地震诱发地质灾害特征与空间分布规律研究[J]. 工程地质学报, 30(5): 1504—1516.
	FAN Xuan-mei, WANG Xin, DAI Lan-xin, et al. 2022. Characteristics and spatial distribution pattern of M_S6.8 Luding Earthquake occurred on September 5, 2022[J]. Journal of Engineering Geology, 30(5): 1504—1516. (in Chinese)
[4]	顾金, 王运生, 曹文正, 等. 2016. 1786年磨西地震烂田湾滑坡形成机制及过程[J]. 山地学报, 34(5): 520—529.
	GU Jin, WANG Yun-sheng, CAO Wen-zheng, et al. 2016. Formation mechanism and motion process of Lantianwan landslide triggered by the 1786 Moxi earthquake[J]. Mountain Research, 34(5): 520—529. (in Chinese)
[5]	金章东, Hilton G R, West J A, 等. 2022. 地震滑坡在活跃造山带侵蚀和风化中的作用: 进展与展望[J]. 中国科学(地球科学), 52(2): 222—237.
	JIN Zhang-dong, Hilton G R, West J A, et al. 2022. The role of earthquake-induced landslides in erosion and weathering from active mountain ranges: Progress and perspectives[J]. Scientia Sinica(Terrae), 52(2): 222—237. (in Chinese)
[6]	李传友, 孙凯, 马骏, 等. 2022. 四川泸定6.8级地震: 鲜水河断裂带磨西段局部发起、全段参与的一次复杂事件[J]. 地震地质, 44(6): 1648—1666.
	LI Chuan-you, SUN Kai, MA Jun, et al. 2022. The 2022 M_S6.8 Luding earthquake: A complicated event by faulting of the Moxi segment of the Xianshuihe fault zone[J]. Seismology and Geology, 44(6): 1648—1666. (in Chinese)
[7]	铁永波, 张宪政, 卢佳燕, 等. 2022. 四川省泸定县 M_S6.8 地震地质灾害发育规律与减灾对策[J]. 水文地质工程地质, 49(6): 1—12.
	TIE Yong-bo, ZHANG Xian-zheng, LU Jia-yan, et al. 2022. Characteristics of geological hazards and it's mitigations of the M_S6.8 earthquake in Luding county, Sichuan Province[J]. Hydrogeology & Engineering Geology, 49(6): 1—12. (in Chinese)
[8]	王敏杰, 李天斌, 孟陆波, 等. 2015. 四川“Y字形”断裂交会部应力场反演分析[J]. 铁道科学与工程学报, 12(5): 1088—1095.
	WANG Min-jie, LI Tian-bin, MENG Lu-bo, et al. 2015. Back analysis of stress field in the intersection region of Y shaped fault, Sichuan[J]. Journal of Railway Science and Engineering, 12(5): 1088—1095. (in Chinese)
[9]	吴俊峰, 王运生, 张桥, 等. 2011. 大渡河加郡—得妥河段大型滑坡地质灾害遥感调查[J]. 水土保持通报, 31(3): 113—116.
	WU Jun-feng, WANG Yun-sheng, ZHANG Qiao, et al. 2011. Investigation on large-scale landslides in Daduhe river between Jiajun county and Detuo county based on remote sensing[J]. Bulletin of Soil and Water Conservation, 31(3): 113—116. (in Chinese)
[10]	许冲, 徐锡伟, 吴熙彦, 等. 2013. 2008年汶川地震滑坡详细编目及其空间分布规律分析[J]. 工程地质学报, 21(1): 25—44.
	XU Chong, XU Xi-wei, WU Xi-yan, et al. 2013. Detailed catalog of landslides triggered by the 2008 Wenchuan earthquake and statistical analyses of their spatial distribution[J]. Journal of Engineering Geology, 21(1): 25—44. (in Chinese)
[11]	杨智勇, 吉锋. 2011. 大渡河干海子滑坡稳定性研究[J]. 防灾减灾工程学报, 31(2): 201—206.
	YANG Zhi-yong, JI Feng. 2011. Research on stability of Ganhaizi landslide in Dadu River Basin[J]. Journal of Disaster Prevention and Mitigation Engineering, 31(2): 201—206. (in Chinese)
[12]	殷跃平. 2008. 汶川八级地震地质灾害研究[J]. 工程地质学报, 16(4): 433—444.
	YIN Yue-ping. 2008. Researches on the geo-hazards triggered by Wenchuan earthquake, Sichuan[J]. Journal of Engineering Geology, 16(4): 433—444. (in Chinese)
[13]	周洪福, 韦玉婷, 王运生, 等. 2017. 1786年磨西地震触发的摩岗岭滑坡演化过程与成因机理[J]. 成都理工大学学报(自然科学版), 44(6): 649—658.
	ZHOU Hong-fu, WEI Yu-ting, WANG Yun-sheng, et al. 2017. Discussion on the formation evolution and genetic mechanism of Mogangling landslide triggered by Moxi earthquake, Sichuan, China[J]. Journal of Chengdu University of Technology(Science & Technology Edition), 44(6): 649—658. (in Chinese)
[14]	Blöthe J, Korup O, Schwanghart W, et al. 2015. Large landslides lie low: Excess topography in the Himalaya-Karakoram ranges[J]. Geology, 43(6): 523—526.
[15]	Burbank D. 2002. Rates of erosion and their implications for exhumation[J]. Mineralogical Magazine, 66(1): 25—52.
[16]	Burbank D, Leland J, Fielding E, et al. 1996. Bedrock incision, rock uplift and threshold hillslopes in the northwestern Himalayas[J]. Nature, 379(6565): 505—510.
[17]	Carson M A, Petley D J. 1970. The Existence of Threshold Hillslopes in the Denudation of the Landscape[J]. Transactions of the Institute of British Geographers, 49: 71—95.
[18]	Clarke B, Burbank D. 2010. Bedrock fracturing, threshold hillslopes, and limits to the magnitude of bedrock landslides[J]. Earth and Planetary Science Letters, 297(3-4): 577—586.
[19]	Densmore A L, Anderson R S, McAdoo B G, et al. 1997. Hillslope evolution by bedrock landslides[J]. Science, 275(5298): 369—372.
[20]	Hales T C, Roering J J. 2007. Climatic controls on frost cracking and implications for the evolution of bedrock landscapes[J]. Journal of Geophysical Research: Earth Surface, 112(F2): 2006JF000616.
[21]	Huang Y D, Xie C C, Li T, et al. 2023. An open-accessed inventory of landslides triggered by the M_S6.8 Luding earthquake, China on September 5, 2022[J]. Earthquake Research Advances, 3(1): 100181.
[22]	Keefer D K. 1984. Landslides caused by earthquakes[J]. Geological Society of America Bulletin, 95(4): 406—421.
[23]	Korup O, Clague J J, Hermanns R L, et al. 2007. Giant landslides, topography, and erosion[J]. Earth and Planetary Science Letters, 261(3-4): 578—589.
[24]	Korup O, Montgomery D R, Hewitt K. 2010. Glacier and landslide feed-backs to topographic relief in the Himalayan syntaxes[J]. Proceedings of the National Academy of Sciences, 107(12): 5317—5322.
[25]	Larsen I J, Montgomery D R, Korup O. 2010. Landslide erosion controlled by hillslope material[J]. Nature Geoscience, 3(4): 247—251.
[26]	Liu W M, Zhou Z, Zhou L Q, et al. 2021. Analysis of hillslope erosion based on excess topography in southeastern Tibet[J]. Frontiers in Earth Science, 9: 684365.
[27]	Malamud B D, Turcotte D L, Guzzetti F, et al. 2004. Landslide inventories and their statistical properties[J]. Earth Surface Processes and Landforms, 29(6): 687—711.
[28]	Montgomery D R. 2001. Slope distributions, threshold hillslopes, and steady-state topography[J]. American Journal of Science, 301(4-5): 432—454.
[29]	Montgomery D R, Brandon M T. 2002. Topographic controls on erosion rates in tectonically active mountain ranges[J]. Earth and Planetary Science Letters, 201(3-4): 481—489.
[30]	Ouimet W B, Whipple K X, Royden L H, et al. 2007. The influence of large landslides on river incision in a transient landscape: Eastern margin of the Tibetan plateau(Sichuan, China)[J]. Geological Society of America Bulletin, 119(11-12): 1462—1476.
[31]	Schmidt K M, Montgomery D R. 1995. Limits to relief[J]. Science, 270(5236): 617—620.
[32]	Schwanghart W, Kuhn N. 2010. TopoToolbox: A set of Matlab functions for topographic analysis[J]. Environmental Modelling & Software, 25(6): 770—781.
[33]	Shao X Y, Xu C, Ma S Y. 2022. Preliminary analysis of coseismic landslides induced by the 1 June 2022 M_S6.1 Lushan earthquake, China[J]. Sustainability, 14(24): 16554.
[34]	Wu C H, Cui P, Li Y S, et al. 2018. Seismogenic fault and topography control on the spatial patterns of landslides triggered by the 2017 Jiuzhaigou earthquake[J]. Journal of Mountain Science, 15(4): 793—807.
[35]	Xu C, Xu X W, Shyu J B H, et al. 2015. Database and spatial distribution of landslides triggered by the Lushan, China M_W6.6 earthquake of 20 April 2013[J]. Geomorphology, 248: 77—92.
[36]	Xu C, Xu X W, Xin Y, et al. 2014. Three(nearly)complete inventories of landslides triggered by the May 12, 2008 Wenchuan M_W7.9 earthquake of China and their spatial distribution statistical analysis[J]. Landslides, 11(3): 441—461.
[37]	Xu C, Xu X W, Yao Q, et al. 2013. GIS-based bivariate statistical modelling for earthquake triggered landslides susceptibility mapping related to the 2008 Wenchuan earthquake, China[J]. Quarterly Journal of Engineering Geology and Hydrogeology, 46(2): 221—236.