Regional bias of landslide data in generating susceptibility maps using logistic regression: Case of Hong Kong Island

On the basis of 1,834 landslide data for Hong Kong Island (HKI), landslide susceptibility maps were generated using logistic regression and GIS. Regional bias of the landslide inventory is examined by dividing the whole HKI into a southern and a northern region, separated by an east-west trending water divide. It was found that the susceptibility map of southern HKI generated by using the southern data differs significantly from that generated by using northern data, and similar conclusion can be drawn for the northern HKI. Therefore, a susceptibility map of HKI was established based on regional data analysis, and it was found to reflect closely the spatial distributions of historical landslides. Elevation appears to be the most dominant factor in controlling landslide occurrence, and this probably reflects that human developments are concentrated at certain elevations on the island. Classification plot, goodness of fit, and occurrence ratio were used to examine the reliability of the proposed susceptibility map. The size of landslide susceptible zones varies depending on the data sets used, thus this demonstrates that the historical landslide data may be biased and affected by human activities and geological settings on a regional basis. Therefore, indiscriminate use of regional-biased data should be avoided.     

基于区域气候模式的流域农业干旱成因分析

以湄公河流域为研究区,采用区域气候模式RegCM3为模拟工具,以根系层土壤含水量为代表性指标,对A1B情景下未来研究区月尺度农业干旱进行了预估。基于地表能量平衡原理,系统分析了降水、蒸发、地表温度和根系层土壤含水量等农业干旱主要影响因素与区域气候模式模拟的大气环流、地表感热通量、地表潜热通量、地表净通量之间的联系和变化规律,从气陆间能量和水汽通量平衡角度,对农业干旱发生机理进行了识别。预估结果表明:从年内各月地表净通量和地表温度变化来看,未来春末(6月)和秋末(10月)湄公河流域温度增加明显,且土壤含水量减少也较为明显;同时,这两个时段蒸发旺盛和降水减少的趋势,有可能导致流域局部地区(尤其是非灌溉农业区)农业干旱的发生。     

Geochemical characteristics of the slip zones of a landslide in granitic saprolite,Hong Kong: implications for their development and microenvironments

Geochemical investigations of the slip zones of a landslide in granitic saprolite revealed that they have signatures distinct from their host materials. These distinctions include stronger Si depletion, higher Al enrichment, greater LOI, significant fixations of Mn, Ba and Ce, stronger negative Eu anomalies, and greater accumulations of other rare earth elements (REE). Altogether, these geochemical characteristics indicate that: (a) the slip zones have greater abundance of clays, consistent with field and microscopic observations; (b) concentration of clay size particles within the slip zones may have been from downward leaching and deposition, and lateral transportation of Al-Si solutions and colloids through pores and fractures within the saprolite; and (c) there were prevailing oxidation and poor drainage, and occasional reduction conditions within the slip zones. It was concluded that geochemical analyses could be effective in gathering clues for understanding the development and nature of slip zones in landslide investigations.     

Study of seasonal climatology and interannual variability over India and its subregions using a regional climate model (RegCM3)

The temporal and spatial variability of the various meteorological parameters over India and its different subregions is high. The Indian subcontinent is surrounded by the complex Himalayan topography in north and the vast oceans in the east, west and south. Such distributions have dominant influence over its climate and thus make the study more complex and challenging. In the present study, the climatology and interannual variability of basic meteorological fields over India and its six homogeneous monsoon subregions (as defined by Indian Institute of Tropical Meteorology (IITM) for all the four meteorological seasons) are analysed using the Regional Climate Model Version 3 (RegCM3). A 22-year (1980–2001) simulation with RegCM3 is carried out to develop such understanding. The National Centre for Environmental Prediction/National Centre for Atmospheric Research, US (NCEP-NCAR) reanalysis 2 (NNRP2) is used as the initial and lateral boundary conditions. The main seasonal features and their variability are represented in model simulation. The temporal variation of precipitation, i.e., the mean annual cycle, is captured over complete India and its homogenous monsoon subregions. The model captured the contribution of seasonal precipitation to the total annual precipitation over India. The model showed variation in the precipitation contribution for some subregions to the total and seasonal precipitation over India. The correlation coefficient (CC) and difference between the coefficient of variation between model fields and the corresponding observations in percentage (COV) is calculated and compared. In most of the cases, the model could represent the magnitude but not the variability. The model processes are found to be more important than in the corresponding observations defining the variability. The model performs quite well over India in capturing the climatology and the meteorological process. The model shows good skills over the relevant subregions during a season.     

东海地球动力学环境与过程的同位素证据及盆地动力学模式

在东海地球动力学环境与过程研究现状分析基础上,讨论了采自盆地东西部油气钻井玄武岩样品的岩石化学、微量元素和同位素测试分析的成果,阐述了玄武岩岩石结构与岩石成分特征,计算岩浆起源深度与岩浆起源温度。通过岩浆源区地幔性质与深部过程分析,指出Sm-Nd、Pb-Pb、Nd-Pb同位素体系反映的深部地幔流体具有古生代向新生代转型的双重特征,与古生代地幔岩浆来源具有较明显亲和性,其中既有古老地幔物质存在,又有新生地幔物质参与,表明研究区地壳深部流体活动十分频繁。结合海洋一期"863"双船折射大剖面有关地质-地球物理解释成果的综合分析认识,提出了盆地地球动力学成因模式。     

西藏玉龙Cu成矿带及其外围地区异常结构模式找矿预测研究

铜矿作为重要的战略性矿产资源之一,备受国家的重视.西藏玉龙斑岩铜(钼)成矿带是中国最大的新生代斑岩铜矿带.纵观国内外重大找矿突破,找矿模式的建立和应用起到了重要的作用.区域地质地球化学异常结构模式找矿预测法已广泛应用于找矿预测评价中.中国的1∶20万和1∶25万区域地球化学调查在矿产勘查工作中发挥了巨大作用,取得了海量的地球化学数据.基于大数据思维,采用新的思路和技术,再挖掘、再开发这些区域地球化学调查数据,开展区域找矿预测评价,应该是实现新的找矿突破的一种重要有效途径.本文利用区域地球化学调查数据,以异常结构模式理论和方法为基础,以玉龙成矿带和已知矿田的区域地球化学异常结构模式为预测评价标准,对玉龙Cu成矿带及其外围地区进行找矿预测研究,划分出有找寻Cu(Mo)及多金属矿前景的7个预测成矿带和19个找矿预测区,显示出玉龙Cu成矿带及其外围地区还具有很大的找矿前景.