RS and GIS-based Statistical Analysis of Secondary Geological Disasters after the 2008 Wenchuan Earthquake

Using RS and GIS means, this article analyzes the general geological characteristics and the structural belt distribution features in Wenchuan County, Sichuan province, P.R. China as well as the characteristics of the large-scale landslides, mud-rock flows, earthquake lakes, etc., after the earthquake on May 12, 2008. Based on the above work, comprehensive indoor and outdoor research is launched on disaster distribution characteristics and their relationship with earthquakes, terrains, strata, lithology, and structures. Weights of evidence method is utilized to quantitatively analyze and evaluate the spatial distribution of secondary geological disasters after the earthquake occurred. 3 remedying grades for secondary geological disasters are derived from the results of the weights of Evidence, followed by suggestions given to remedy earthquake secondary disasters.

Risk Assessment of Secondary Geological Disasters Induced by the Yushu Earthquake

The Yushu Ms 7.1 earthquake occurred on April 14,2010 in Qinghai Province,China.It induced a mass of secondary geological disasters,such as collapses,landslides,and debris flows.Risk assessment maps are important for geological disaster prevention and mitigation,and also can serve as a guide for post-earthquake reconstruction.Firstly,a hazard assessment index system of secondary geological disasters in the earthquake region was built in this paper,which was based on detailed analysis of environmental and triggering factors closely related to geological disasters in the study area.GIS technology was utilized to extract and analyze the assessment index.Hazard assessment maps of secondary geological disasters were obtained by spatial modeling and overlaying analysis.Secondly,an analysis of the vulnerability of hazard bearing bodies in the area was conducted,important information,such as, population density,percentage of arable land, industrial and agricultural outputs per unit area were regarded as assessment indices to evaluate socioeconomic vulnerability.Thirdly,the risk level of secondary geological disasters of the area was obtained by the formula:Risk=Hazard×Vulnerability. Risk assessment maps were categorized into four levels,including"low","moderate","high"and"very high".These results show that some urban areas are at very high risk,including Jiegu,Chengwen,Xiaxiula and Sahuteng towns.This research can provide some references and suggestions to improve decisionmaking support for emergency relief and post- earthquake reconstruction in the study area.

Characteristics and Prevention of Secondary Geological Disasters of Wenchuan Earthquake

In the research, secondary geological disasters of Wenchuan earthquake were defined and the consequences were illustrated based on geological disasters, such as collapse, landslide and debris flow, and threats of barrier lakes. In addition, the characteristics of secondary disasters were analyzed, as follows： Rupture of geological faults lays foundation in terms of geological structure; loose solids provide resources of an earthquake; abundant rainfall and large runoffs are driving forces of an earthquake; rainstorm, flood, and long-term high temperature are major inducing factors. Furthermore, suggestions on prevention of secondary disasters were proposed in terms of prevention before, at and after an earthquake. Finally, the scientific and practical significances of secondary disasters were illustrated.

Factor analysis of earthquake-induced geological disasters of the M7.0 Lushan earthquake in China

The seismic intensities, lithologic characteristics and terrain features from a 3000 km2-region near the epicenter of the Lushan earthquake are used to analyze earthquake-induced geological disaster. The preliminary results indicate that secondary effects of the earthquake will affect specific areas, including those with glutenite and carbonate bedrock, a seismic intensity of IX, slopes between 40° and 50°, elevations of less than 2500 m, slope change rates between 20° and 30°, slope curvatures from - 1 to -0.5 and 0. 5 to 1, and relief between 50 and 100 m. Regions with susceptibility indices greater than 0.71 are prone to landslides and collapses. The secondary features are mainly distributed on both sides of the ridges that extend from Baosheng to Shuangshi and from Baosheng to Longxing. Other features are scattered on both sides of the ridges that extend from Qishuping to Baosheng and from Masangping to Lingguan. The distribution of the earthquake-related features trends in the NE direction, and the area that was most affected by the Lushan earthquake covers approximately 52.4 km^2.

Types and Causes of Debris Flow Damage to Drainage Channels in the Wenchuan Earthquake Area

Debris flows are among the most common geological disasters in China,and have been particularly frequent in Sichuan Province since the Wenchuan earthquake on 12 May 2008.The construction of debris flow drainage channels is a countermeasure used to distribute debris flow fans,and these channels play a critical role in the mitigation and prevention of damage resulting from debris flows.Under field conditions,the useful life of drainage channels can be greatly shortened as a result of strong abrasions to the drainage structure caused by the debris flow.Field investigations have shown that the types of damage to drainage channels include(a) erosion caused by hyper-concentrated silt flow,(b) impact fractures and foundation scour at the groundsills of the drainage channel,(c) destruction of the drainage channel outlet,and(d) destruction of the drainage channel caused by debris flow abrasion.In addition,based on the destruction of the drainage channel during the debris flow drainage process,a new type of drainage channel with energy dissipation components was proposed and applied in a steep,narrow gully for debris flow mitigation.Moreover,design and engineering repair recommendations for drainage channels are provided as a reference for repairing the damage to the channel.The results can provide an important reference for the effective repair and optimal design of drainage channels.

Assessment of prospective hazards resulting from the 2017 earthquake at the world heritage site Jiuzhaigou Valley, Sichuan, China

On August 8, 2017, a Ms = 7.0 magnitude earthquake occurred in the Jiuzhaigou Valley, in Sichuan Province, China(N: 33.20°, E: 103.82°). Jiuzhaigou Valley is an area recognized and listed as a world heritage site by UNESCO in 1992. Data analysis and field survey were conducted on the landslide, collapse, and debris flow gully, to assess the coseismic geological hazards generated by the earthquake using an unmanned aerial vehicle(UAV), remote-sensing imaging, laser range finders, geological radars, and cameras. The results highlighted the occurrence of 13 landslides, 70 collapses, and 25 potential debris flow gullies following the earthquake. The hazards were classified on the basis of their size and the potential property loss attributable to them. Consequently, 14 large-scale hazards, 30 medium-sized hazards, and 64 small hazards accounting for 13%, 28%, and 59% of the total hazards, respectively, were identified. Based on the variation tendency of the geological hazards that ensued in areas affected by the Kanto earthquake(Japan), Chi-chi earthquake(Taiwan China), and Wenchuan earthquake(Sichuan China), the study predicts that, depending on the rain intensity cycle, the duration of geological hazard activities in the Jiuzhaigou Valley may last over ten years and will gradually decrease for the following five to ten yearsbefore returning to pre-earthquake levels. Thus,necessary monitoring and early warning systems must be implemented to ensure the safety of residents,workers and tourists during the construction of engineering projects and reopening of scenic sites to the public.

Progress and Prospects of the Natural Restoration of Damaged Vegetation after the Earthquake

Vegetation plays an important role in soil and water conservation, water conservation and carbon sequestration of an ecosystem. The restoration of damaged vegetation is of great significance to the maintenance of species diversity and the restoration of the regional ecological environment. It is also one of the most effective measures to improve the fragile ecosystem. This paper summarizes the research results from decades of damaged vegetation recovery in the process of vegetation recovery, the main driving factor and the restoration mode.

The formation of the Wulipo landslide and the resulting debris flow in Dujiangyan City, China

The Wulipo landslide, triggered by heavy rainfall on July 10, 2013, transformed into debris flow,resulted in the destruction of 12 houses, 44 deaths, and 117 missing. Our systematic investigation has led to the following results and to a new understanding about the formation and evolution process of this hazard. The fundamental factors of the formation of the landslide are a high-steep free surface at the front of the slide mass and the sandstone-mudstone mixed stratum structure of the slope. The inducing factor of the landslide is hydrostatic and hydrodynamic pressure change caused by heavy continuous rainfall. The geological mechanical model of the landslide can be summarized as "instability-translational slide-tension fracture-collapse" and the formation mechanism as "translational landslide induced by heavy rainfall". The total volume of the landslide is 124.6×104 m3, and 16.3% of the sliding mass was dropped down from the cliff and transformed into debris flow during the sliding process, which enlarged 46.7% of the original sliding deposit area. The final accumulation area is found to be 9.2×104 m2. The hazard is a typical example of a disaster chain involving landslide and its induced debris flow. The concealment and disaster chain effect is the main reason for the heavy damage. In future risk assessment, it is suggested to enhance the research onpotential landslide identification for weakly intercalated slopes. By considering the influence of the behaviors of landslide-induced debris flow, the disaster area could be determined more reasonably.

Earthquake disaster chain model based on complex networks for urban engineering systems

According to news reports on severe earthquakes since 2008,a total of 51 cases with magnitudes of 6.0 or above were analyzed,and 14 frequently occurring secondary disasters were identified.A disaster chain model was developed using principles from complex network theory.The vulnerability and risk level of each edge in this model were calculated,and high-risk edges and disaster chains were identified.The analysis reveals that the edge“floods→building collapses”has the highest vulnerability.Implementing measures to mitigate this edge is crucial for delaying the spread of secondary disasters.The highest risk is associated with the edge“building collapses→casualties,”and increased risks are also identified for chains such as“earthquake→building collapses→casualties,”“earthquake→landslides and debris flows→dammed lakes,”and“dammed lakes→floods→building collapses.”Following an earthquake,the prompt implementation of measures is crucial to effectively disrupt these chains and minimize the damage from secondary disasters.

Earthquake Resistant Engineering and Application of Seismic Zonation Map of ChinaTechnicalInnovations

China is a country with high seismicity. It is very important for industry and structure to fortify against earthquakes. In this paper the outline of seismicity in China, the criteria for fortification against earthquakes and the contents of seismic zonation map of China are described. The contents of seismic safety evaluation for major construction projects, such as large dams, large bridges, long distance pipe lines for transporting oil and natural gas, nuclear plants, petrochemical enterprises and so on, are presented. Some geological disasters caused by destructive earthquake, such as earthquake caused collapse and landslide, liquefaction of saturated soil and earthquake fault and so on, are also presented. Preventive countermeasures for these disasters are discussed.

川西地区中小学防震减灾科普现状及需求研究——以四所中小学校为例

为摸清川西地区中小学的防震减灾需求,选取川西地区雅安市雨城区太平实验小学、甘孜州丹巴县城区第一学校、天全中学、泸定中学4所中小学校开展防震减灾科普现状及需求的调查研究。研究结果显示,川西少数民族地区中小学现有防震减灾科普产品种类、呈现形式比较单一,科普产品针对性较弱;川西地区对防震减灾科普产品的需求更趋向地震风险防范、地震应急救援等知识的系统学习。本研究结果可为今后更好地研发有针对性的防震减灾科普产品和开展地域性防震减灾科普工作提供依据。

泸定地震诱发灾害特征分析

2022年9月5日,四川省泸定县海螺沟景区发生6.8级地震,震中烈度Ⅸ度。相较于2008年汶川8级地震和2013年芦山7级地震,此次地震震级要小,但是地震区为山区,地质灾害发育,造成交通中断、118人死亡或失踪。为探究泸定地震损失情况,作者对泸定县和石棉县的主要地震影响区进行了为期5 d的考察。基于考察成果和区域地质资料,对地质灾害孕育、建筑结构震损和人员伤亡情况进行了分析,以期为灾后重建提供参考。主要结论如下:1)地质灾害的上盘效应不突出,灾害主要分布于烈度Ⅶ度及其以上地区,规模小,以崩塌或落石和浅层滑坡为主,偶见基岩平面滑动和土体圆弧形滑动。2)地质灾害形式受地质条件控制。泸定县得妥镇以上为干热河谷,山坡卸荷较强,风化程度低,主要灾害形式为落石;得妥镇以下降雨量相对较大,山坡卸荷、风化严重,主要灾害形式为浅层滑坡。3)地质灾害主要出现在山脊、陡缓坡交接部位、侵蚀沟槽两壁,以及公路沿线。工程扰动是地质灾害密集分布和人员伤亡的促发因素。4)建筑结构震损主要出现在Ⅸ度烈度区,以磨西镇的震损最为严重。农村自建房屋和老旧建筑施工质量是影响结构抗震能力的主要问题,灾后重建房屋选址需要考虑场地效应影响。5)在高山峡谷地区,公路边坡加固和建筑结构避开落石影响区是降低地震伤亡率的有效措施。

城市地震次生火灾蔓延模型研究

地震次生火灾是震后发生最为频繁和造成灾害损失最为严重的次生灾害。随着城市化进程的加快,原本城乡结合处的老旧建筑成片区大量存在,一旦地震发生,建筑破坏尤为严重,区域建筑密集等因素为次生火灾的发生和蔓延提供了基础条件,因此对城市地震次生火灾研究显得尤为重要。从工程应用出发,通过确定火灾蔓延的经验参数,建立了基于建筑的城市地震次生火灾蔓延模型,模型主要包括建筑内火灾蔓延和相邻建筑之间的火灾蔓延两个过程,模型中考虑了建筑结构类型、地震对建筑破坏、风速和风向和相邻建筑蔓延的极限距离等影响因素对蔓延的影响。利用1995年日本阪神大地震中水笠公园周边建筑火灾蔓延实际数据,与本文建立的模型模拟结果进行对比分析,说明该模型具有较好的可信度。

泸定地震人员死亡、失联数量的变化特征及地质灾害对其的影响

搜集了泸定6.8级地震人员死亡和失联资料,通过与近10年典型破坏性地震震例进行案例对比,定量分析了泸定地震人员死亡、失联数量随时间变化的特征。结合应急救援工作实际,梳理、归纳主要原因,同时系统分析了地质灾害对人员死亡率及失联率的影响。探讨山区地震灾害及救灾特点,提出山区复杂环境下地震灾害信息核查报送及人员搜救能力提升建议。

2024年1月23日新疆乌什M_(S)7.1地震地质灾害和地表破裂

2024年1月23日新疆乌什M_(S)7.1地震是自1992年吉尔吉斯斯坦Suusamyr M_(S)7.3地震以来发生在天山地震带内的最大地震。主余震初步精定位和第一时间野外调查结果表明,乌什MS7.1地震的余震带总体走向NE,长约62km,主要分布在盆山交接部位。地震产生了边坡失稳、岩崩、滚石、地裂隙等次生地质灾害,主要集中在沿构造走向微观震中两侧30km范围内。由微观震中向N约7km、向S约13km以外,地质灾害迅速减轻,且山前断层陡坎(F_(5))未见任何新鲜的活动迹象。结合中国地震局地质研究所产出的InSAR同震形变场初步结果,判定此次主震的发震断层为一条倾向NW、未错出地表的逆冲断层。在GCMT震中所在的恰勒玛提河,沿西域砾岩背斜南翼发现了总体走向N60°E、长约2km、最大垂直位错约1m的地震地表破裂带。该地表破裂在较老地貌面上基本沿先存断层陡坎发育,总体受一条倾向SE、与主震发震断层倾向相反的逆断裂控制。地表破裂带长2km,规模远小于乌什M_(S)7.1地震余震带,其是由M_(S)7.1主震所致还是因M_(S)5.7余震造成的,以及产生地表破裂的SE倾逆断层与NW倾主震发震断裂之间是何种关系,还需进一步研究。

日本能登半岛7.6级地震灾害特点分析

2024年1月1日日本能登半岛发生7.6级地震,造成大量人员伤亡和严重经济损失。地震引发海啸、核电站事故及大量滑坡、滚石、崩塌等地质灾害,造成通信、道路、电力、水利等基础设施不同程度破坏。本文从地壳变化、救灾持续时间、次生灾害、救灾事故、基础设施破坏、避难场所等6个方面对此次地震的灾害特点进行了总结,同时对日本应急响应情况进行了论述,最后从提高建筑物抗震能力、加大地震风险防范和做好大震巨灾防范与应对准备三个方面提出我国应对大震巨灾的建议。

甘肃积石山Ms 6.2地震次生地质灾害分布规律与发育特征

地震是诱发山区地质灾害最主要的原因之一.受发震构造、岩体强度、地貌形态等的综合影响,地震诱发的次生地质灾害通常具有显著的分布规律和发育特征,揭示该规律对抗震救灾和风险评估具有极为重要的支撑作用.2023年12月18日23:59,甘肃省积石山保安族东乡族撒拉族自治县发生Ms 6.2级地震,在甘肃省和青海省造成严重的人员伤亡和财产损失,地震导致部分在册地质灾害隐患点危害加剧,同时诱发大量新生地质灾害,以崩塌、滑坡、泥石流为主要类型.震后,通过快速的遥感解译和实地调查,获取了此次地震次生地质灾害隐患数据集,结果显示地震导致新生崩塌灾害多于滑坡,而诱发滑坡数量相对较少,加剧泥石流的数量不多;空间特征表现为受逆冲构造“上下盘效应”和软弱黄土地质环境的显著控制;地貌条件,尤其是坡度、坡向和相对高差显著影响同震灾害的空间分布.

新时期我国重大地震和地质灾害应急管理与实践

中国是世界上地震灾害、地质灾害最为严重的国家之一,地震和地质灾害应急工作对应急快速反应能力的要求是各类自然灾害应急中比较高的,也是难度比较大的。本文通过总结分析我国的地震和地质灾害形势以及近年来典型灾害事件,从强化底线思维、强化抗灾基础、强化应急准备、强化基层应急、强化应急处置五个方面梳理并探讨了地震和地质灾害的应急管理对策。

地震诱发煤矿次生灾害类型与评估方法

为解决煤矿承灾体受地震灾害影响易发生次生灾害风险的问题,首先,调查和分析典型案例,归纳总结煤矿次生灾害类型与破坏特征,并基于人、机、环、管全要素,构建地震诱发煤矿次生灾害风险评估三级指标体系;然后,提出风险等级和隐患重要度评估方法;最后,以河北省某市煤矿为例开展实际应用。结果表明:地震诱发煤矿次生灾害类型按照承灾体分为6类;地震诱发煤矿次生灾害发生可能性评估主要考虑煤矿所在区域地震灾害等级、煤矿次生灾害危险性、煤层瓦斯赋存致灾性、矿井水文地质条件致灾性、承灾体设防水平、防灾减灾能力6方面,后果严重性评估主要考虑灾害可能造成的伤亡人数和经济损失2方面;该市煤矿抗震设防薄弱环节为通风系统、井筒支护系统、排水系统,应有针对性地提高抗震设防等级。

矿震机理及其次生灾害监测技术研究进展

矿震是一种深部矿井开采必然出现的动力现象,随着煤矿开采深度增加,发生频率和影响范围呈现上升趋势,复合煤岩动力灾害频发,严重威胁煤矿安全开采,对“双碳”目标的实现造成恶劣的影响。安全、精准和可靠的监测手段是矿震灾害防治的基础与前提,微震监测系统依靠矿震波信号能够准确反映煤岩状态并且提前进行风险评价,已被广泛应用于井下矿震监测。本文围绕矿震识别、微震监测以及次生灾害预警三个方面进行综述。回顾了矿震机理与识别分类的发展过程,分析了微震监测技术的特征信号、影响因素以及制约瓶颈,按照监测目的、信号采集方式和频带区间等分类标准对微震监测技术进行了简要介绍和评述。在此基础上,通过现场案例以及实验研究分析,详细阐述了矿震作为煤岩动力灾害前兆预警信息的理论依据与初步探索。总结了当前微震监测系统覆盖区域小和矿震监测尺度需求大之间的矛盾。结合地震监测台网宏观尺度验证与微震监测的微观定位分析优势,提出了远距离非接触式矿震监测台网的想法。为未来矿震机理与前兆信息预警的发展和研究提供了新的思路。