突发地质灾害气象预警统计模型与应用

通过引入地质灾害潜势度,突发地质灾害气象预警统计模型解决了雨量判据法不能明确表达地质环境条件的问题,在此基础上,提出了潜势度计算、大气降雨变量设计、预警方程优化3方面的改进方法。为提高潜势度计算的准确性,增加了基于卡方检验的地质环境因子独立性判别步骤;对地质环境因子确信程度初始值和权值计算中确信程度变化量初始值设置进行了规定;并将预警模型中累计雨量修正为更为合理的有效累计雨量。在现有的预警方程的基础上提出了基于联合概率分析的预警方程,避免了其与基本地质认识和物理规律存在一定距离、方程系数的意义不明确的局限。以2009年7月2日发布的24 h雨量预报为例,计算结果表明：虽然预报区域面积从101 008 km²减小到27 553 km²,但是地质灾害点落入预报区的比例从44%增加到62%。这说明通过改进的预警模型理论上更加严密,空间准确率有所提高,空报率有所下降。     

基于深反射地震剖面的沂沭断裂带岩石圈精细结构

为揭示沂沭断裂带深部结构及发生—发展过程,查清断裂切割深度及对岩石圈地幔的破坏,探讨沂沭断裂带的构造组合样式、运动方式、地壳稳定性及其对资源环境的约束作用,研究团队于2019年在沂沭断裂带南段沂南—莒县附近布设了一条长约60 km的深反射地震剖面,系统采集了沂沭断裂带和两侧地块的地震数据,对沂沭断裂带深部岩石圈精细结构进行了解剖.结果显示,该区岩石圈结构在横向上表现为以沂沭断裂带为界的块状结构特征,地壳厚度约30.8～39.5 km;莫霍面总体呈西浅东深态势,并被西倾的沂水—汤头断裂(F2)和昌邑—大店断裂(F4)错断,垂直落差达10.5 km.与浅部"两堑夹一垒"的构造组合样式不同的是,沂沭断裂带在深部剖面上表现为由沂水—汤头断裂(F2)和昌邑—大店断裂(F4)向上延伸与分叉散开的多条断裂组成"双枝状"构造组合样式.断裂带内被断层切割的界面反射波多呈向上的拱弧形,其构造形迹具有伸展、挤压和走滑并存的特征,推断这些界面为层间滑脱构造,它们指示了沂沭断裂带"多层滑移"构造运动方式.该断裂带不仅切穿了近地表、壳内地质界面,F2、F4断裂还向下切割莫霍面,深入岩石圈地幔,是深达地幔的深大断裂构造带,为地幔热物质的上涌提供了通道,对中生代的岩浆活动和内生成矿具有控制作用.地震剖面西端的铜井金矿成矿与沿F2断裂上侵的铜井杂岩体关系密切;剖面东端的火山机构保存完整,没有明显构造破坏痕迹,据此认为沂沭断裂带左行走滑主要发生在早白垩世青山期以前,其后水平滑移量应不大.从区域地质分布及地震反演结果看,昌邑—大店断裂(F4)明显将山东省分割为鲁西和鲁东两个地质构造单元,因此将其作为区域地质构造分界线是合理的.本项研究结果进一步加深了沂沭断裂带深、浅部结构的认识,为分析研究沂沭断裂带的深部过程和浅部构造响应及对资源环境的影响提供了资料约束.     

A novel index to evaluate discretization methods:A case study of flood susceptibility assessment based on random forest

The selection of a suitable discretization method(DM)to discretize spatially continuous variables(SCVs)is critical in ML-based natural hazard susceptibility assessment.However,few studies start to consider the influence due to the selected DMs and how to efficiently select a suitable DM for each SCV.These issues were well addressed in this study.The information loss rate(ILR),an index based on the informa-tion entropy,seems can be used to select optimal DM for each SCV.However,the ILR fails to show the actual influence of discretization because such index only considers the total amount of information of the discretized variables departing from the original SCV.Facing this issue,we propose an index,infor-mation change rate(ICR),that focuses on the changed amount of information due to the discretization based on each cell,enabling the identification of the optimal DM.We develop a case study with Random Forest(training/testing ratio of 7:3)to assess flood susceptibility in Wanan County,China.The area under the curve-based and susceptibility maps-based approaches were presented to compare the ILR and ICR.The results show the ICR-based optimal DMs are more rational than the ILR-based ones in both cases.Moreover,we observed the ILR values are unnaturally small(＜1％),whereas the ICR values are obviously more in line with general recognition(usually 10％-30％).The above results all demonstrate the superiority of the ICR.We consider this study fills up the existing research gaps,improving the ML-based natural hazard susceptibility assessments.     

滇东伊迪卡拉（震旦）系顶部旧城段多样宏体化石群的发现?

中国云南东部晋宁、江川地区的伊迪卡拉（震旦）系顶部灯影组旧城段新发现了多样的宏体化石群，除了丰富的Vendotaenia与Tyrasotaenia类化石以外，以形体较大的Tawuia类和Longfengshaniaceae科等具固着构造的底栖多细胞藻类化石占据优势，另有一些形态奇特、亲缘关系不明的宏体化石，该组合与华南陡山沱组和灯影组石板滩段的宏体化石组合相比存在着明显的差别。依据形态特征，本文概述了部分产自江川旧城段的具有不同类型固着构造的底栖藻类和归属不明的宏体化石特征。华南滇东地区旧城段形态多样的宏体藻类化石的发现，进一步表明伊迪卡拉纪末期存在后生植物的多样化发展。这一时期浮游微生物和后生植物的共同繁盛可能为早寒武世“澄江生物群”的爆发奠定了生态基础。     

Vulnerability of population and transportation infrastructure at the east bank of Delaware Bay due to coastal flooding in sea-level rise conditions

Catastrophic flooding associated with sea-level rise and change of hurricane patterns has put the northeastern coastal regions of the United States at a greater risk. In this paper, we predict coastal flooding at the east bank of Delaware Bay and analyze the resulting impact on residents and transportation infrastructure. The three-dimensional coastal ocean model FVCOM coupled with a two-dimensional shallow water model is used to simulate hydrodynamic flooding from coastal ocean water with fine-resolution meshes, and a topography-based hydrologic method is applied to estimate inland flooding due to precipitation. The entire flooded areas with a range of storm intensity (i.e., no storm, 10-, and 50-year storm) and sea-level rise (i.e., current, 10-, and 50-year sea level) are thus determined. The populations in the study region in 10 and 50 years are predicted using an economic-demographic model. With the aid of ArcGIS, detailed analysis of affected population and transportation systems including highway networks, railroads, and bridges is presented for all of the flood scenarios. It is concluded that sea-level rise will lead to a substantial increase in vulnerability of residents and transportation infrastructure to storm floods, and such a flood tends to affect more population in Cape May County but more transportation facilities in Cumberland County, New Jersey.     

Mixing of event and pre‐event water in a shallow Entisol in sloping farmland based on isotopic and hydrometric measurements,SW China

Water percolation and flow processes in subsurface geologic media play an important role in determining the water source for plants and the transport of contaminants or nutrients, which is essential for water resource management and the development of measures for pollution mitigation. During June 2013, the dynamics of the rainwater, soil water, subsurface flows and groundwater in a shallow Entisol on sloping farmland were monitored using a hydrometric and isotopic approach. The results showed that effective mixing of rainwater and soil water occurred in hours. The rebound phenomenon of δD profiles in soils showed that most isotope‐depleted rainwater largely bypassed the soil matrix when the water saturation in the soil was high. Preferential‐flow, which was the dominant water movement pattern in the vadose zone, occurred through the whole soil profile, and infrequent piston‐flow was mainly found at 20–40 cm in depth. The interflow in the soil layer, composed of 75.2% rainwater, was only generated when the soil profile had been saturated. Underflow in the fractured mudrock was the dominant flow type in this hillslope, and outflow was dominated by base flow (groundwater flow) with a mean contribution of 76.7%. The generation mechanism of underflow was groundwater ridging, which was superimposed upon preferential‐flow composed mainly of rainwater. The quick mixing process of rainwater and soil water and the rapid movement of the mixture through preferential channels in the study soil, which shows a typical bimodal pore size distribution, can explain the prompt release of pre‐event water in subsurface flow. Water sources of subsurface flows at peak discharge could be affected by the antecedent soil water content, rain characteristics and antecedent groundwater levels. Copyright © 2016 John Wiley & Sons, Ltd.     

The evolution of rock failure with discontinuities due to shear creep

A two-dimensional brittle creep model for rock provides insight into the initiation of shear fracture along weak discontinuities in rock. The model accounts for material heterogeneity and introduces the concept of a mesoscopic renormalization to capture the cooperative interaction between cracks in the transition from distributed to localized damage. A series of shear creep tests on rock with discontinuities were performed to simulate the initiation and propagation of crack along a pre-existing weakness under sustained shear stress and normal stress. The investigation showed that shear stress level and the normal stress level might have significant effect on the long-term behavior of rock with weak discontinuities. Moreover, a case study of rock slope instability was also investigated, where the numerically simulated instability failure of rock slope with discontinuities showed that both tensile and shear damage at the weakest elements are the trigger for the failure surface initiation in the rock slope. Once damage occurs, redistributed stress concentrations would then intensify fracture propagation and coalescence within these damage zones, leading to the progressive development of a failure surface. Moreover, failure surface extending is not only dominated by the properties and the position of discontinuities but also influenced remarkably by the complex interaction between existing discontinuities and fracture propagation. The results are of general interest because they can be applied to the investigation of time-dependent instability in rock masses, to the mitigation of associated rock hazards in rock engineering, and even to a better understanding of the physical phenomena governing the stability of rock slope.     

中强地震前山东地下流体地震前兆模糊分维特征研究

采用模糊集理论与分形理论相结合的模糊分维方法，计算山东地下流体在１９８３年菏泽５．９级地震和１９９５年苍山５．２级地震前的变化。分析结果认为，模糊分维值反映了地震前兆时序观测资料的结构变化特征，具有一定的物理意义，为从复杂的地下流体前兆观测值中提取地震异常信息提供了新的方法，但对某些台、测项而言、必须具体分析其模糊分维变化特征及其震前异常变化特征。     

Study on Three-dimensional Visualization for Rock Structure

The visualization of rock structure is a very useful and important technique in many aspects in geological and geotechnical engineering such as investigating and evaluating the stability of a high rock slope. The conventional method used to visualize rock structure is limited to plotting the orientation of individual discontinuities by using the Schmidt stereographic net. The present paper shows a new technique to visualize the three-dimensional structure of rock masses. The fitting function for three-dimensional rock structure was established based on data gathered from field survey. Two fitting methods by which the discontinuous points gathered from a plane and discrete points from field survey were fitted respectively are suggested. The technique to visualize the three-dimensional structure of rock masses includes many aspects such as projection transformation, blanking and mutual cutting, are investigated. Based on the visualizing technique, the rock structure at the site of Xilupdu dam which is being built in Southwest of China was investigated.     

A three-dimensional large-deformation random finite-element study of landslide runout considering spatially varying soil

Landslides - Landslide is a uniquely dynamic large-deformation process that can present serious threat to human lives and infrastructures. The natural soil properties often exhibit inherent spatial...