Seismically induced landslide displacements: a predictive model

Newmark's model for predicting earthquake-induced landslide displacements provides a simple way to predict the coseismic displacements affecting a sliding mass subject to earthquake loading. In this model, seismic slope stability is measured in terms of critical acceleration, which depends on the mechanical soil properties, pore-pressure distribution, and slope geometry. The triggering seismic forces are investigated in terms of energy radiation from the source, propagation, and site effects, based on 190 accelerometric recordings from 17 Italian earthquakes with magnitudes between 4.5 and 6.8. The method is based on the calibration of relations having the general form of an attenuation law that relates the energy of the seismic forces to the dynamic shear resistances of the sliding mass to propagate the expected landslide displacements as an inverse function of the distance from the fault rupture; the amount of displacement computed through these relations provides a criterion to predict the occurrence of slope failures. Finally, maps showing, in a deterministic and a probabilistic way, the potential of seismically induced landslide displacements are displayed as a tool to provide seismic landslide scenarios and earthquake-induced landslide hazard maps, respectively.     

Hydrogeology of a coal-seam gas exploration area, southeastern British Columbia, Canada: Part 1. Groundwater flow systems

Discovery of high contents of methane gas in coals of the Mist Mountain Formation in the Elk River valley, southeastern British Columbia, Canada, has led to increased exploration activity for coal-seam gas (CSG). CSG production requires groundwater abstraction to depressurize the coal beds and to facilitate methane flow to the production wells. Groundwater abstraction will have hydrodynamic effects on the flow system, and an understanding of the groundwater flow system is needed to evaluate these effects. The purpose of this paper is to describe the groundwater flow system in the area by means of a groundwater flow model and interpretation of hydrochemical and isotopic analyses of groundwater and surface water. Groundwater flow for the Weary Creek exploration area is modeled in two vertical sections. The model domains, based on classic upland–lowland conceptual flow models, are approximately 10,000 m long and 4,000 m deep. Each consists of a fixed water-table boundary and no-flow boundaries along the traces of major faults. Steady-state groundwater flow is calibrated to hydraulic-head, streamflow, and groundwater-recharge data. Simulated steady-state velocity fields define regional and local flow components consistent with the conceptual model. The results are consistent with regional trends in δ²H, δ¹⁸O, tritium, and TDS, which define two distinct groundwater groups (A and B) and a third of intermediate composition. An active, shallow, local flow component (group A) is recharged in beds cropping out along subdued ridges; this component discharges as seeps along lower and mid-slope positions in the southern part of the study area. The waters are tritiated, relatively enriched in δ²H and δ¹⁸O, and have low TDS. A deeper regional flow component (group B), which originates at a higher altitude and which discharges to the Elk River valley bottom, is characterized by non-tritiated groundwater with relatively depleted δ²H and δ¹⁸O, and higher TDS. Groundwater contributes less than 10% of the total direct flow to the Elk River, as indicated by flow measurements and by the absence of group A and group B characteristics in the river water. Thus it is hypothesized that groundwater extraction during CSG production will have little impact on the river. The groundwater flow model developed in this work is used in a companion paper to further test this hypothesis. Electronic Publication     

土体应力-应变关系转型问题分析

通过对土体应力应变试验结果的分析,明确指出了土体普遍存在的应力-应变关系转型现象。提出了按后破坏模量和临界围压两个参数判别土体应力-应变关系转型的方法,对影响土体应力-应变关系转型的因素包括土的类型、围压、初始密度或含水率、排水条件及应力路径等进行了简要分析。最后,对砂土初步提出了一个能反映转型现象的组合应力-应变关系模型的理论框架。     

全球对外直接投资的新特点

投资自由是经济全球化的重要动力机制,随着世界经济全球化程度不断加深,对外直接投资（ＦＤＩ）出现了许多新特点,以资源优化配置带动的ＦＤＩ迅猛发展,跨国公司的生产经营和研究开发活动日益全球化,企业的跨国并购加剧,本文运用翔实的资料,对全球ＦＤＩ的新特点进行了分析研究。     

雷达定量降水动态分级Z-I关系估算方法

利用高时空分辨率的雷达定量降水估测和预报(RQPE和RQPF)对洪水监测、发布洪水警报起重要指导作用，目前国内外对其研究的方法主要采用概率配对法、Z-I关系法和基于Z-I关系的数学算法校正法，这些方法均存在强调某一因素忽略其它因素的问题，并且对短时强降水，尤其是极强降水低估严重。从统计和个例两方面对比分析了四种雷达定量降水方法的误差，致力于寻找一种将雷达回波反射率预报场反演为降水场时误差较小的技术方法，能改进对短时强降水、特别是极强降水严重低估问题的方法，并且该方法也能在业务应用中方便、快速、精确实现。对比研究结果表明：动态分级Z-I关系法是一种对雷达QPE和回波反射率预报场反演降水场都较好的方法，并且改进了对短时强降水、尤其是大于55 mm/h的短时极强降水低估的问题；在业务计算中仅需15秒，能满足6分钟更新一次计算结果的需要，而且不依赖气候统计，便于移植。     

基于重力模型的中国城市体系空间联系与层域划分

新中国成立以来,中国大陆城市体系空间格局发生了深刻的变化。传统的城市体系空间联系主要从人流、物流、技术流、信息流、金融流进行数据的收集和分析,也有运用图论原理进行Rd链分析。近来,随着社会主义市场经济的迅速发展,城市之间的联系变得异常复杂、数据不易得到。本文试图运用重力模型方法对中国城市间的空间联系强度进行定量计算,据此刻画中国城市体系的空间联系状态和结节区结构。从研究结果看,所得结论与实际情况基本吻合。     

Operational Evaluation of the Quantitative Precipitation Estimation by a CINRAD-SA Dual Polarization Radar System

In this paper, the quantitative precipitation estimation based on hydrometeor classification (HCA-QPE) algorithm was proposed for the first operational S band dual-polarization radar promoted by the CINRAD/SA radar of China. The HCA-QPE algorithm, the localized Colorado State University-Hydrometeor Identification of Rainfall (CSU-HIDRO) and Joint Polarization Experiment (JPOLE) algorithms, and the dynamic Z-R relationships based on variational correction QPE (DRVC-QPE) algorithm were evaluated with the rainfall events from March 1 to October 30, 2017 in the Guangdong Province. The results indicated that even though the HCA-QPE algorithm did not use the observed rainfall data for correction, its estimation accuracy was better than that of the DRVC-QPE algorithm when the rainfall rate was greater than 5mm h^(-1); and the stronger the rainfall intensity, the greater the QPE improvement. And the HCA-QPE algorithm worked better than the localized CSU-HIDRO and JPOLE algorithms. This study preliminarily verified the improved accuracy of QPE by a dual-polarization radar system modified from CINRAD-SA radar.     

地闪回击电流测量综述

地闪回击电流是雷电的一个重要特征参数。其测量数据的积累对于雷电防护技术的提高具有重要意义。目前国内外的雷电研究人员通过矮塔、高塔直接观测，人工引雷观测和电场电流关系反衍的方法对地闪回击电流进行了大量的观测研究，并取得了丰富的观测资料。观测表明，负地闪首次回击电流平均为30kA，继后回击电流平均12kA。正地闪回击电流平均为35kA，有时可达几百kA。不同地区地闪回击电流平均值略有不同。高塔测量是主要的雷电流参量直接测量方法，但不同高度测量的地闪回击电流无论峰值还是波形都存在一定的差异。人工引发闪电和自然闪电继后回击雷电流的测量结果较为一致。间接估测雷电流参数的方法随着地闪回击模式的发展将成为主要的方法之一。     

MLP在雷达定量降水估测中的应用

通过临近时次、临近空间降水回波性质相似假设,以人工智能技术结合快速动态分级法(Fast Dynamic Categorical method,FDC)为核心,设计广西区域分钟级雷达定量降水估测产品模型。在单部雷达估测降水时,分两层三次使用感知器寻求合理的降水类型分类Z-I关系,首先将FDC看为一种多分类算法,根据单站雷达各级回波的降水估测结果误差将回波区内的站点分为强站点和弱站点两类,然后分别对这两类站点再次使用FDC建立新的强、弱两类Z-I关系。在多部雷达组网联合估测定量降水时,将各雷达估测值等权重看待,将单部雷达估测作为一个分支,通过连结方式构建一个多层感知器(Multilayer Perceptron,MLP)。无站点回波区采用K近邻算法(K-Nearest Neighbor,KNN)选择合适的MLP求得的Z-I关系估算降水量。对2019年3—10月试验产品进行检验分析,结果表明以区域站组成的训练组小时降水相关系数达0.973 7,以国家级气象台站组成的测试组相关系数达0.825 6。     

Influences of the unsaturated,saturated, and riparian zones on the transport of nitrate near the Merced River,California, USA

Transport and transformation of nitrate was evaluated along a 1-km groundwater transect from an almond orchard to the Merced River, California, USA, within an irrigated agricultural setting. As indicated by measurements of pore-water nitrate and modeling using the root zone water quality model, about 63% of the applied nitrogen was transported through a 6.5-m unsaturated zone. Transport times from recharge locations to the edge of a riparian zone ranged from approximately 6 months to greater than 100 years. This allowed for partial denitrification in horizons having mildly reducing conditions, and essentially no denitrification in horizons with oxidizing conditions. Transport times across a 50–100-m-wide riparian zone of less than a year to over 6 years and more strongly reducing conditions resulted in greater rates of denitrification. Isotopic measurements and concentrations of excess N₂ in water were indicative of denitrification with the highest rates below the Merced River. Discharge of water and nitrate into the river was dependent on gradients driven by irrigation or river stage. The results suggest that the assimilative capacity for nitrate of the groundwater system, and particularly the riverbed, is limiting the nitrate load to the Merced River in the study area.