Necessity of integrated methodology for hazard mitigation of quake lakes:case study of the Wenchuan Earthquake,China

The massive 8.0-magnitude Wenchuan Earthquake triggered huge landslides,avalanches,and debris flows that blocked rivers and created 34 important quake lakes,including the Tangjiashan Quake Lake on the Tongkou River.More than half of these lakes were identified to be of moderate or high hazard levels,so activities needed to be undertaken for hazard mitigation of potential flooding.This paper presents the mitigation processes of quake lake hazards,which involve various techniques such as rapid hazard analysis,scenario-based mitigation planning,and real-time forecasting of outburst flooding for implementation actions.The shortage of hydrologic and geological data and the nature of emergency situations raise substantial challenges in the hazard mitigation of quake lakes.This paper suggests a potential approach in dealing with quake lake hazards,which integrates the automatic monitoring network,hydrologic models,and hydrodynamic models with a comprehensive indicator for hazard levels.The necessity of improving the integrated methodology is highlighted.

Ground fissure hazards in USA and China

Tremendous losses were caused by ground fissure hazard both in USA and China. Six states of southwestern USA and seven provinces of central China were affected by the destructive ground fissures. The aseismic ground fissure hazards usually take place in land subsidence area. The comparison of the two countries' ground fissures were given including ground fissure formation, evolution, mechanics of destruction and countermeasures against them. The destructive ground fissures occurred about a half century earlier in USA than in China The mechanisms of various ground fissures were analyzed with interdisciplinary studies. It has been found that the preexisted faults are serving as the bases of forming modem ground fissure, and human activities, e.g. over pumping ground water, or oil, can accelerate the creeping of the fissures and make them destructive to many kinds of civil engineering. The countermeasures to mitigate ground fissure hazard were put forward, not only in science and technology but also in social administration. The successful practices in the two countries were introduced as examples.

Relationships between Potential Risk of Hazardous Material Releases and Socio-Economic Demographic Characteristics Using Geospatial Analysis

The problem investigated in this research is about the potential risk of technological hazards, which poses a perilous threat to humankind and the environment. Rapid urbanization has been increasing the population density in an area, elevating the risk of exposure to technological disasters. Therefore, it is necessary to detect the areas with higher chemical risk to spread awareness about the potential risk zones and reduce actual damage and casualties resulting from the hazardous substance events. The basic design of the study utilizes geospatial analysis to map the TRI (Toxics Release Inventory) facilities in the communities of Texas to establish a relationship between potential hazardous material release zones and the human population at risk. The study identified the vulnerable counties as well as investigated how those risk areas are related to race/ethnicity, income and education. The research would contribute to the policymakers acting on the hazard situation and keep them better prepared for chemical hazards. In addition, it would help the residents and emergency managers to better understand the circumstance to mitigate the consequences as well as increase their awareness to be ready for the uncertainties in the hotspots involved in high risk of the hazards.

Probability Forecast of Regional Landslide Based on Numerical Weather Forecast

The regional forecast of landslide is one of the key points of hazard mitigation. It is also a hot and difficult point in research field. To solve this problem has become urgent task along with Chinese economy fast development. This paper analyzes the principle of regional landslide forecast and the factors for forecasting. The method of a combination of Information Value Model and Extension Model has been put forward to be as the forecast model. Using new result of Numerical Weather Foreeast Research and that combination model, we discuss the implementation feasibility of regional landslide forecast. Finally, with the help of Geographic Information System, an operation system for southwest of China landslide forecast has been developed. It can carry out regional landslide forecast daily and has been pilot run in NMC. Since this is the first time linking theoretical research with meteorological service, further works are needed to enhance it.

An experimental study on tsunami inundation over complex coastal topography

In recent studies, the effects of complex costal topography on tsunami run-up has sparked heated discussion. This study mainly aims at investigating the effects of complex costal topography on the tsunami inundation distance and the effectiveness of sand dunes in dissipating tsunami wave energy. The experiments were carried out in a wave flume to investigate the potential reduction effects of wave run-up by non erodible sand dune like features. The results show that increasing dunes spacing could not significantly affect inundation distance. However, if the height of sand dunes is of the same order of magnitude as the incoming tsunami wave and the gaps between the dunes are large enough, successful tsunami mitigation could also be possible.

Poisson's ratios and S-wave velocities of the Xishancun landslide,Sichuan,China,inferred from high-frequency receiver functions of local earthquakes

Landslides are recurrent geological phenomena on Earth that cause heavy casualties and property losses annually.In this study,we use the V_(p)-k stacking and nonlinear waveform inversion methods of high-frequency receiver functions extracted from local earthquakes,to sequentially invert Poisson’s ratios and S-wave velocities of the Quaternary Xishancun landslide,which is composed of three segments,i.e.,h1,h2,and h3 from bottom to top.Our results show that Poisson’s ratio values are generally higher than 0.33 and that the S-wave velocities vary from 0.1 to 0.9 km s^(-1).High Poisson’s ratios(>0.44)are mainly distributed in the juncture regions between different segments,as well as the western edge of h2.These zones show significant variation in landslide thickness and are potentially hazardous areas.Low velocities of 0.05–0.2 km s^(-1)with thicknesses of 10–30m are widely observed in the lower layer of the landslide.The high Poisson’s ratios and low-velocity layer may be related to water-rich materials in these areas.Our study suggests that the high-frequency receiver functions from local earthquakes can be used to delineate geotechnical structures,which is valuable for landslide stability analysis and hazard mitigation.

Quantitative Risk Analysis of a Rainfall-Induced Complex Landslide in Wanzhou County,Three Gorges Reservoir,China

On 4 April 2013,a 1.5 million cubic meter landslide occurred in Sunjia Town,Wanzhou County,Three Gorges Reservoir,China.After initiation,the Sunjia landslide traveled about 30 m toward the northeast and destroyed most of the infrastructure in its path.The landslide was triggered by heavy rainfall and previous slope excavations,but this slope also displayed a complicated failure process:the overlying earth slope first deformed and then induced sliding along underlying rock surfaces.Surface displacements that resulted from continuous creeping of the post-event slope were observed by an emergency monitoring system that revealed the disequilibrium state of the slope.To discuss the stability and future movements of the remaining unstable debris deposits,we developed a geotechnical model of the post-slide slope,calculated how it can slide again in an extreme rainfall scenario,and estimated the potential runout distance using the Tsunami Squares method.We then estimated the number of people and the value of the infrastructure threatened by this potential landslide.Lastly,we analyzed the vulnerability of elements at risk and quantitatively evaluated the hazard risk associated with the most dangerous scenario.This quantitative risk analysis provides a better understanding of,and technical routes for,hazard mitigation of rainfallinduced complex landslides.

Optimized Hot Spot and Directional Distribution Analyses Characterize the Spatiotemporal Variation of Large Wildfires in Washington,USA,1970-2020

Spatiotemporal analysis of fire activity is vital for determining why wildfires occur where they do,assessing wildfire risks,and developing locally relevant wildfire risk reduction strategies.Using various spatial statistical methods,we determined hot spots of large wildfires(>100 acres)in Washington,the United States,and mapped spatiotemporal variations in large wildfire activity from 1970 to 2020.Our results found that all hot spots are located east of the crest of the Cascade Range.Our spatiotemporal analysis found that the geographic area wherein most of the state’s acres burned has shrunk considerably since 1970 and has become concentrated over the north-central portion of the state over time.This concentration of large wildfire activity in north-central Washington was previously unquantified and may provide important information for hazard mitigation efforts in that area.Our results highlight the advantages of using spatial statistical methods that could aid the development of natural hazard mitigation plans and risk reduction strategies by characterizing previous hazard occurrences spatially and spatiotemporally.