Spatial Distribution of Seismic Landslides in the Areas of 1927 Gulang M8.0 Earthquake

The 1927 Gulang M8.0 earthquake has triggered a huge number of landslides, resulting in massive loss of people''s life and property. However, integrated investigations and results regarding the landslides triggered by this earthquake are rare; such situation hinders the deep understanding of these landslides such as scale, extent, and distribution. With the support of Google Earth software, this study intends to finish the seismic landslides interpretation work in the areas of Gulang earthquake (VIII-XI degree) using the artificial visual interpretation method, and further analyze the spatial distribution and impact factors of these landslides. The results show that the earthquake has triggered at least 936 landslides in the VIII-XI degree zone, with a total landslide area of 58.6 km². The dense area of seismic landslides is located in the middle and southern parts of the X intensity circle. Statistical analysis shows that seismic landslides is mainly controlled by factors such as elevation, slope gradient, slope direction, strata, seismic intensity, faults and rivers. The elevation of 2 000-2 800 m is the high-incidence interval of the landslide. The landslide density is larger with a higher slope gradient. East and west directions are the dominant sliding directions. The areas with Cretaceous and Quaternary strata are the main areas of the Gulang seismic landslides. The X intensity zone triggered the most landslides. In addition, landslides often occur in regions near rivers and faults. This paper provides a scientific reference for exploring the development regularities of landslides triggered by the 1927 Gulang earthquake and effectively mitigating the landslide disasters of the earthquake.     

潜在地震滑坡危险区区划方法

不同地区地震活动的强度和频率是不同的.基于地震危险性分析的地震滑坡危险研究在综合了地震烈度、位置、复发时间等因素的基础上,考虑了地震动峰值加速度时空分布的特点,可以有效地应用于潜在地震滑坡危险区区划.以汶川地震灾区为研究对象,根据研究区的地质构造、地震活动特点等划分出灾区的潜在震源区,对该区进行地震危险性分析,并在此基础上采用综合指标法做出基于地震危险性分析的地震滑坡危险性区划.所得地震滑坡危险性区划按照滑坡危险程度分为高危险、较高危险、较低危险和低危险四级,表示未来一段时间内研究区在遭受一定超越概率水平的地震动作用下,不同地区地震滑坡发生的可能程度. 本文给出的地震滑坡危险性区划结果中,汶川地震滑坡崩塌较发育的汶川、北川、茂县等部分区域均处于高危险或较高危险区域;在对具有较高DEM精度的北川擂鼓镇地区所作的地震滑坡危险性区划中,汶川地震中实际发生的地震滑坡灾害与地震滑坡危险区划结果表现出较好的一致性.对区域范围而言,基于地震危险性分析的地震滑坡区划,可为初期阶段的土地规划使用及重大工程选址提供参考.     

Hazard Assessment of Co-seismic Landslides Based on Information Value Method: A Case in 2018 MW6.6 Hokkaido Earthquake, Japan

An M_W6.6 earthquake occurred in eastern Hokkaido, Japan on September 6^th, 2018. Based on the pre-earthquake image from Google Earth and the post-earthquake image from high resolution (3 m) planet satellite, we manually interpret 9 293 coseismic landslides and select 7 influencing factors of seismic landslide, such as elevation, slope, slope direction, road distance, flow distance, peak ground acceleration (PGA) and lithology. Then, 9 293 landslide points are randomly divided into training samples and validation samples with a proportion of 7:3. In detail, the training sample has 6 505 landslide points and the validation sample has 2 788 landslide points. The hazard risk assessment of seismic landslide is conducted by using the information value method and the study area is further divided into five risk grades, including very low risk area, low risk area, moderate risk area high risk area and very high risk area. The results show that there are 7 576 landslides in high risk area and very high risk area, accounting for 81.52% of the total landslide number, and the landslide area is 22.93 km², accounting for 74.35% of the total area. The hazard zoning is in high accordance with the actual situation. The evaluation results are tested by using the curve of cumulative percentage of hazardous area and cumulative percentage of landslides number. The results show that the success rate of the information value method is 78.50% and the prediction rate is 78.43%. The evaluation results are satisfactory, indicating that the hazard risk assessment results based on information value method may provide scientific reference for landslide hazard risk assessment as well as the disaster prevention and mitigation in the study area.     

STUDY ON THE DISTRIBUTION PATTERN OF EARTHQUAKE- TRIGGERED LANDSLIDES BASED ON SEISMIC LANDSLIDE SUSCEPTIBILITY ANALYSIS: A CASE STUDY OF LANDSLIDES TRIGGERED BY THE MS6.5 LUDIAN EARTHQUAKE IN 2014

On August 3, 2014, an M_W6.5 earthquake occurred in Ludian County, Yunnan Province, which triggered significant landslides and caused serious ground damages and casualties. Compared with the existing events of earthquake-triggered landslides, the spatial distribution of co-seismic landslides during the Ludian earthquake showed a special pattern. The relationship between the co-seismic landslides and the epicenter or the known faults is not obvious, and the maximum landslide density doesn't appear in the area near the epicenter. Peak ground acceleration (PGA), which usually is used to judge the limit boundary of co-seismic landslide distribution, cannot explain this distribution pattern. Instead of correlating geological and topographic factors with the co-seismic landslide distribution pattern, this study focuses on analyzing the influence of seismic landslide susceptibility on the co-seismic distribution. Seismic landslide susceptibility comes from a calculation of critical acceleration values using a simplified Newmark block model analysis and represents slope stability under seismic loading. Both DEM (SRTM 90m)and geological map (1 ︰ 200^￣￣000)are used as inputs to calculate critical acceleration values. Results show that the most susceptible slopes with the smallest critical accelerations are generally concentrated along the banks of rivers. The stable slopes, which have the larger critical accelerations and are comparably stable, are in the places adjacent to the epicenter. Comparison of the distribution of slope stability and the real landslides triggered by the 2014 M_W6.1 Ludian earthquake shows a good spatial correlation, meaning seismic landslide susceptibility controls the co-seismic landslide distributions to a certain degree. Moreover, our study provides a plausible explanation on the special distribution pattern of Ludian earthquake triggered landslides. Also the paper discusses the advantages of using the seismic landslide susceptibility as a basic map, which will offer an additional tool that can be used to assist in post-disaster response activities as well as seismic landslides hazards zonation.     

基于Newmark模型的概率地震滑坡危险性分析方法研究

本文以天水地区为研究区,结合地震潜在震源区模型和Newmark位移预测方程,采用概率地震危险性分析方法,计算了该地区50年超越概率10%水平下的Newmark位移。同时,根据天水地区50年超越概率10%下的阿里亚斯烈度,并结合Newmark位移与阿里亚斯烈度的关系式,计算了天水地区在遭受50年超越概率10%下的阿里亚斯烈度影响时,潜在滑坡体产生的Newmark位移分布。通过比较上述两种方法得到的天水地区不同Newmark位移的分布特征,本文认为二者虽然存在较大差异,但其空间分布特征均能反映天水地区每个场点处的相对滑坡危险性。对滑坡危险性水平进行分区的结果显示,天水地区60%以上的区域具有高地震滑坡危险性,50%以上的区域具有甚高地震滑坡危险性。本文的研究结果可以作为天水地区地震危险性及风险评估的参考资料,也可以作为天水地区城市规划、土地使用规划、地震应急准备以及其它公共政策制定的参考资料。      

黄土地震滑坡卫星影像识别方法

为获得详细的地震滑坡数据和分布特征,揭示黄土地震滑坡的成灾模式和防治措施,需要对黄土地区地震滑坡进行详细的编录,利用卫星影像的识别方法是重要的手段之一。通过总结黄土地震滑坡特有的空间分布特征、平面形态特征、地震滑坡发育特征和伴生水文特征,归纳利用卫星影像识别黄土地震滑坡的7种识别标志。利用该方法,研究通渭地区黄土地震滑坡的空间分布与规律,结果表明：黄土地震滑坡卫星影像识别方法获得的滑坡与野外现场调查结果相近;通渭地区滑坡拥有缓坡发育、低角度、中远滑距、大体积、方向性明显等特点。     

Landslide Amplification by Liquefaction of Runout‐Path Material after the 2008 Wenchuan (M 8·0) Earthquake,China

Here, we propose that an earthquake can trigger the failure of a landslide mass while simultaneously triggering liquefaction of runout‐path materials before the arrival of the landslide mass, thus greatly increasing the size and mobility of an overriding landslide. During the 2008 Wenchuan earthquake, about 60 000 landslides were triggered, directly resulting in about 20 000 casualties. While these landslides mainly originated from steep slopes, some landslides with high mobility formed in colluvial valley deposits. Among these, the most catastrophic was the Xiejiadian landslide in Pengzhou city, which traveled hundreds of meters before coming to rest. Through field investigation and laboratory testing, we conclude that this landslide primarily formed from colluvial deposits in the valley and secondarily from failure of slopes in granitic rock located uphill. Much of the granitic slope failure was deposited in the upper part of the travel path (near the slide head); the remainder was dispersed throughout the main landslide deposit. Superposition of deposits at the landslide toe indicates that landslide debris derived from colluvial soil was deposited first. The deposits at the landslide toe displayed flow characteristics, such as fine materials comprising basal layers and large boulders covering the deposit surface. We hypothesize that the main part of the landslide resulted from seismogenic liquefaction of valley colluvium, rather than from liquefaction potentially caused by undrained loading from the granitic slope failures impacting the colluvium. To examine the likelihood that seismogenic liquefaction occurred, we took samples from different areas of the landslide deposit and performed undrained cyclic shear tests on them in the laboratory. The results showed that the sandy soils that comprise most of the deposit are highly liquefiable under seismic loading. Therefore, we conclude that liquefaction of the colluvium in the valley during the earthquake was the main reason for this rapid (~46 m/s) long‐runout (1·7 km) landslide. Copyright © 2012 John Wiley & Sons, Ltd.     

数值模拟在地震小区划滑坡灾害评价中的应用

工程场地地震安全性评价、特别是在地震小区划工作中,对地震滑坡的评价通常采用定性分析方法,因此,对其影响范围未给出定量的评价结果。本文以吕梁新城地震小区划滑坡评价为例,通过对该区的地质条件、地貌特征的研究,针对具有典型特征的剖面,选取地震力、内聚力、摩擦角作为影响因子,采用离散单元法(DEM)对潜在滑坡体的稳定性进行了数值模拟计算,得到了可能失稳的滑坡体潜在滑动的影响范围。并在此基础上通过对已知滑坡与潜在滑坡剖面结构特征的类比,对整个研究区内滑坡体的影响范围进行了评价。研究结果可为吕梁新城的规划提供依据,也可为同类工程中地震滑坡灾害的定量评价提供参考。     

黄土高原地震作用下黄土滑坡滑距预测方法

为评估黄土高原地区地震滑坡致灾区域,提出一种基于模糊信息优化处理的地震滑坡滑距预测方法。在野外调查、室内试验和分析的基础上,对黄土高原的地震滑坡类型、性质和影响因素进行分析。以摩根斯坦-普莱斯法计算黄土边坡的稳定性,建立边坡最小安全系数与影响因素的关系,其影响因素主要包括地震烈度、比高、坡角、容重、内黏聚力、内摩擦角等,并在此基础上得到纯黄土地震滑坡滑距的影响关系。将黄土高原地区数次大震中采集到的93个样本数据进行归纳分析,建立模糊信息优化处理模型。所得的计算结果通过误差校验和与其他滑坡滑距预测方法进行对比,来证明本模型有较高的准确性。最后对天水市22个潜在滑坡的边坡进行滑距预测。     

黄土随机振动强度参数在地震滑坡分析中的应用

地震滑坡往往是黄土地区最突出而且最严重的灾害类型。为了寻求黄土地区震害预测方法,作者选择了位于1920年海原大震10度区内的回回川滑坡进行具体研究。分析中运用了输入随机地震动时程的不规则波动三轴仪强度试验所得的参数。在稳定性分析中采用了求解临界地震系数的方法,反演得出回回川滑坡形成前原始斜坡坡角为5°—15°的安全系数为3.3,是一个相当稳定的斜坡。而在地震力作用下,在具有相当于地震烈度8度强或9度弱的地震动加速度时就产生滑动。反演结果与实际较吻合,说明本文提出的方法是分析滑坡形成规律和对黄土斜坡进行稳定性分析的切合实际且较为准确的方法。     

Spatial distribution analysis of landslides triggered by the 2013-04-20 Lushan earthquake,China

The 2013-04-20 Lushan earthquake(seismic magnitude Ms 7.0 according to the State Seismological Bureau)induced a large number of landslides.In this study,spatial characteristics of landslides are developed by interpreting digital aerial photography data.Seven towns near the epicenter,with an area of about 11.11 km2,were severely affected by the earthquake,and 703 landslides were identified from April 24,2013 aerial photography data over an area of 1.185 km2.About 55.56% of the landslide area was less than 1000 m2,whereas about 3.23 % was more than 10,000 m2.Rock falls and shallow landslides were the most commonly observed types in the study area,and were primarily located in the center of Lushan County.Most landslide areas were widely distributed near river channels and along roads.Five main factors were chosen to study the distribution characteristics of landslides:elevation,slope gradients,fault,geologic unit and river system.The spatial distribution of coseismal landslides is studied statistically using both landslide point density(LPD),defined as the number of landslides(LS Number)per square kilometer,and landslide area density(LAD),interpreted as the percentage of landslides area affected by earthquake.The results show that both LPD and LAD have strong positive correlations with five main factors.Most landslides occurred in the gradient range of 40°-50° and an elevation range of 1.0-1.5 km above sea level.Statistical results also indicate that landslides were mainly formed in soft rocks such as mudstone and sandstone,and concentrated in IX intensity areas.     

GIS‐based regional landslide susceptibility mapping: a case study in southern California

Landslides threaten lives and property throughout the United States, causing in excess of $2 billion in damages and 25–50 deaths annually. In regions subjected to urban expansion caused by population growth and/or increased storm intensities caused by changing climate patterns, the economic and society costs of landslides will continue to rise. Using a geographic information system (GIS), this paper develops and implements a multivariate statistical approach for mapping landslide susceptibility. The presented susceptibility maps are intended to help in the design of hazard mitigation and land development policies at regional scales. The paper presents (a) a GIS‐based multivariate statistical approach for mapping landslide susceptibility, (b) several dimensionless landslide susceptibility indexes developed to quantify and weight the influence of individual categories for given potential risk factors on landslides and (c) a case study in southern California, which uses 11 111 seismic landslide scars collected from previous efforts and 5389 landslide scars newly digitized from local geologic maps. In the case study, seven potential risk factors were selected to map landslide susceptibility. Ground slope and event precipitation were the most important factors, followed by land cover, surface curvature, proximity to fault, elevation and proximity to coastline. The developed landslide susceptibility maps show that areas classified as having high or very high susceptibilities contained 71% of the digitized landslide scars and 90% of the seismic landslide scars while only occupying 26% of the total study area. These areas mostly have ground slopes higher than 46% and 2‐year, 6‐hour precipitation greater than 51 mm. Only 12% of digitized landslides and less than 1% of recorded seismic landslides were located in areas classified as low or very low susceptibility, while occupying 42% of the total study region. These areas mostly have slopes less than 27% and 2‐year, 6‐hour precipitation less than 41 mm. Copyright © 2007 John Wiley & Sons, Ltd.     

区域地震滑坡灾害定量评估研究进展和展望

地震滑坡是最常见的地震次生地质灾害之一,不仅带来环境恶化,通常还造成严重的人员伤亡和财产损失,因此备受关注。为了解地震滑坡研究发展趋势,凝练地震滑坡定量评估科学问题,文章对区域地震滑坡定量评估起源、发展现状、存在的问题及未来发展进行了系统总结。研究结果表明：(1)区域地震滑坡灾害定量评估研究兴起于20世纪80年代,经过50多年学者的不懈努力,取得了丰硕的成果。区域地震滑坡灾害定量评估研究面临着新的社会需求。(2)地震滑坡是地震动力、地质特征和地貌条件等多因素耦合作用的结果,地震滑坡现象只有考虑成因机理与动力过程方可解释,地震滑坡成因机理研究主要集中于强震条件下斜坡的动力响应规律分析。(3)地震滑坡发育特征、成因机理以及数据库建设等基础研究推动了地震滑坡灾害风险定量评估研究。区域地震滑坡灾害风险定量评估包括地震滑坡危险性定量评估、地震滑坡易损性定量评估、地震滑坡危害性定量评估等内容。(4)在区域地震滑坡灾害定量评估方面,还需要进一步探索区域地震滑坡灾害形成的系统性和时空分布规律性、改进和完善区域地震滑坡灾害风险定量评估方法、开拓区域地震滑坡灾害防治战略规划。     

GIS支持下的地震诱发滑坡危险区预测研究

为了满足对地震诱发滑坡危险区预测的不断增长的迫切要求，灾害评价成为帮助决策过程重要的基础工具之一。即使地震滑坡危险性各组份的评价很困难，但地理信息可辅助提出这种灾害制图的有关方法。描述了用于地理信息系统识别和定量计算不同地震滑坡危险区的技术方法，确定了地震烈度、地形坡度、岩土体类型和现存滑坡密度共4个因子参与的地震诱发滑坡危险性分析。在ARC／INFO DRID支持下，进行叠合分析，由此编制了云南省地震诱发滑坡危险区预测图。由地貌学家提出的地震诱发滑坡预测为规划和工程师提供了对区域规划和建筑工程有价值的技术方法。     

Landslide inventories and their statistical properties

Landslides are generally associated with a trigger, such as an earthquake, a rapid snowmelt or a large storm. The landslide event can include a single landslide or many thousands. The frequency–area (or volume) distribution of a landslide event quanti?es the number of landslides that occur at different sizes. We examine three well‐documented landslide events, from Italy, Guatemala and the USA, each with a different triggering mechanism, and ?nd that the landslide areas for all three are well approximated by the same three‐parameter inverse‐gamma distribution. For small landslide areas this distribution has an exponential ‘roll‐over’ and for medium and large landslide areas decays as a power‐law with exponent ‐2·40. One implication of this landslide distribution is that the mean area of landslides in the distribution is independent of the size of the event. We also introduce a landslide‐event magnitude scale m_L = log(N_LT), with N_LT the total number of landslides associated with a trigger. If a landslide‐event inventory is incomplete (i.e. smaller landslides are not included), the partial inventory can be compared with our landslide probability distribution, and the corresponding landslide‐event magnitude inferred. This technique can be applied to inventories of historical landslides, inferring the total number of landslides that occurred over geologic time, and how many of these have been erased by erosion, vegetation, and human activity. We have also considered three rockfall‐dominated inventories, and ?nd that the frequency–size distributions differ substantially from those associated with other landslide types. We suggest that our proposed frequency–size distribution for landslides (excluding rockfalls) will be useful in quantifying the severity of landslide events and the contribution of landslides to erosion. Copyright © 2004 John Wiley & Sons, Ltd.     

Earthquake-reactivated landslide scenarios in Southern Italy based on spectral-matching input analysis

The Tyrrhenian portion of the Calabria region (southern Italy) is particularly prone to landslides as a consequence of intense morphodynamic processes. These processes affect the slopes that are composed of highly jointed metamorphic rock masses. Moreover, the frequent intense rainfalls and the up to Mw 7.0 regional earthquakes represent the main landslide triggering factors. An area of approximately $45\,\hbox {km}^{2}$ was selected as a test site in the context of a regional project aimed at reconstructing possible earthquake-reactivated landslide scenarios (i.e., referred to already existing landslide masses). An inventory map led to the identification of 175 landslides, including rock slides, earth slides and rock falls. Ground-motion scenarios based on a spectral-matching method were derived to evaluate the expected earthquake-induced displacements of the existing landslides. Naturally recorded acceleration time histories were selected from international ground-motion databases based on a similarity index and considered representative of the seismological features of the considered seismic sources (i.e., epicentral distance, magnitude, focal mechanism). Spectral attenuation was considered, according to well-established attenuation laws, to define the expected response spectrum at the outcropping bedrock corresponding to each existing landslide. Subsequently, the selected natural records were modified to guarantee spectral matching with the attenuated response spectra at each landslide site. The derived time histories were used to compute co-seismic displacements via the classic Newmark’s sliding-block method. Different scenarios of co-seismic landslide displacements or collapse were generated for different pore-water pressure hypotheses. The strongest $\hbox {Mw}>6$ seismic scenario (Messina Straits seismogenic source) indicated an exceedance probability of earthquake-induced co-seismic landslide collapse varying from 20 to 55 % with the increasing severity of the pore-water pressures. This probability corresponds to a percentage of co-seismic landslide displacements up to 40 % of the total inventoried landslides. The exceedance probability indicated that co-seismic landslide collapse drops below 20 % for $\hbox {Mw}<6$ seismic scenarios. In contrast, if a uniform probability is assumed for the seismic action occurrence, i.e., return periods of 475 and 2,475 years, the total percentage of landslide co-seismic displacements could be as high as 70 and 90 %, respectively, for the considered pore-water pressures.     

An open-accessed inventory of landslides triggered by the MS 6.8 Luding earthquake,China on September 5, 2022

This study constructs a preliminary inventory of landslides triggered by the M_S 6.8 Luding earthquake based on field investigation and human-computer interaction visual interpretation on optical satellite images. The results show that this earthquake triggered at least 5 007 landslides, with a total landslide area of 17.36 ?km², of which the smallest landslide area is 65 ?m² and the largest landslide area reaches 120 747 ?m², with an average landslide area of about 3 500 ?m². The obtained landslides are concentrated in the IX intensity zone and the northeast side of the seismogenic fault, and the area density and point density of landslides are 13.8%, and 35.73 ?km^?2 peaks with 2 ?km as the search radius. It should be noted that the number of landslides obtained in this paper will be lower than the actual situation because some areas are covered by clouds and there are no available post-earthquake remote sensing images. Based on the available post-earthquake remote sensing images, the number of landslides triggered by this earthquake is roughly estimated to be up to 10 000. This study can be used to support further research on the distribution pattern and risk evaluation of the coseismic landslides in the region, and the prevention and control of landslide hazards in the seismic area.     

基于降雨入渗的Newmark模型改进及地震滑坡危险性预测研究

滑坡是一种破坏性非常强的地质灾害,其中地震与降雨均为诱导滑坡发生的关键因素。从降雨期间发生地震的角度考虑,基于Green-Ampt降雨入渗模型对Newmark模型进行改进,推导两因素耦合作用下的边坡安全系数F_S。以云南省鲁甸县某一区域为例,分别开展无降雨、降雨无积水与降雨积水三种情况下的地震滑坡危险性预测及坡度与入渗深度因子对位移影响分析。通过比较上述三种情况,得到研究区域内的Newmark累积位移分布及危险性区划。结果表明：与未降雨情况相比,后两种情况下地震滑坡高危险程度区域面积占比计算区域随着降雨时间的增加从1%分别提高至9%、12%,滑坡低危险程度区域面积从51%分别降低至35%、33%;坡度值与入渗深度值越大,滑坡位移越大,危险性越高。Newmark改进模型充分考虑了降雨对地震滑坡产生的促进作用,能更好地反映出研究区每个场点相对的滑坡危险性,对滑坡危险性预测具有一定指导意义。     

汶川地震滑坡危险性评价——以武都区和文县为例

利用GIS技术详细研究汶川地震在甘肃省陇南市武都区和文县触发的滑坡地质灾害的分布规律及其与地震烈度、地形坡度、断层、高程、地层岩性的相关关系,采用基于GIS的加权信息量模型的崩塌滑坡危险性评价方法,对研究区的地震滑坡危险性进行学科分析。结果表明：极高危险区在高程上主要分布在集水高程区,高度危险区主要沿白水江、白龙江等主干河流两侧极高易发区的边界向两侧扩展,轻度和极轻度危险区面积占比较小,主要分布在低烈度、活动断裂不发育、人类活动微弱的高海拔地区,另外国道G215沿极高危险性区域分布明显;利用危险性等级分区结果统计人口公里格网数据,得到武都区和文县潜在影响人口,发现研究区约78万人将受到地震滑坡灾害的潜在影响。