地震长期效应对黄土力学性质的影响

黄土高原地区,具有大孔隙、弱胶结特征的黄土遭遇地震荷载影响后,其内部结构受到扰动,微结构的变化会在后期物理力学性质中集中反映出来。通过动三轴试验对原状黄土试样进行模拟历史地震预处理,对处理试样依次进行饱和、固结、不排水剪切试验。结果表明:黄土试样的初始含水率为10%时,经历历史地震扰动的黄土较未扰动黄土相比,其偏应力明显增加,孔隙水压力降低,抗剪强度指标值增大3.42 kPa和2.67°;当初始含水率增加至15%时,历史地震产生的长期效应将引起后期黄土强度持续增大,增幅远远超过10%的黄土试样,黏聚力和内摩擦角达到3.98 kPa和3.02°。通过扫描电镜试验和压汞试验,从微观角度分析地震长期效应对黄土力学性质影响的内在机制,结果发现历史地震引起黄土内部颗粒移动、孔隙结构变化是黄土强度增加的重要因素。     

Holocene-historical volcanism and active faults as natural risk factors for Armenia and adjacent countries

Examples of Holocene-historical volcanism in the territory of Armenia and adjacent areas of Eastern Anatolia and Western Iran are discussed. Holocene-historical activity is proved for the volcanoes of Tskhouk–Karckar, Porak, Vaiyots-Sar, Smbatassar and Ararat. Based on the analysis of remote sensing data, field work, and historical and archeological information, it is demonstrated that there was a considerable number of cases of volcanic activity in Armenia and adjacent regions of Turkey, Syria and Iran during the historical period. The Holocene volcanic centers are situated within pull-apart basin structures and controlled by active faults. Situated in an area prone to many types of natural hazards, Armenia and adjacent countries face high natural risk. The evidence presented shows that volcanic hazard also contributes to the natural risk for these countries.     

地理空间系统史料库构建的几个问题

本文结合甘肃等地的区域地理信息数据库构架研究,分析了史料库建设的薄弱环节和主要问题提出以同步建库的技术路线,保持当期历史数据体的完整性;以差别化构建的原则组织历史数据,确保完整入库,防止史料散失.     

A multi‐century record of linked nearshore and coastal change

Using geographic information system (GIS) and field measurements the nearshore morphological variability of a headland bay beach at Tenby, West Wales (51·66 N; –4·71 W) was assessed over historical timeframes (1748–2007). Three areas chosen for detailed analysis were the area between mean low water (MLW) and lowest astronomical tide (LAT) contours; LAT and one fathom contours; and one and two fathom contours. Estuary closure c. 1855 has been suggested as the genesis for long‐term beach evolution and did have an initial effect, with northward dune migration and reduced flushing effects. However, this research suggests nearshore bank migration and retrogradation associated with spit collapse took place prior to closure and continued throughout the assessed timeframe. Historical data revealed patterns of shoreward migration demonstrated by changes in orientation, Giltar headland acting as a pivot. Variations in sandbank position correlated with areal reduction of both Giltar spit and White Bank. Temporal offshore areal loss was contrasted against variable gains inshore as offshore banks welded to the beachface. Annual volumetric change analyses represented by profiles that extend 1 km offshore, confirmed Giltar spit and White Bank erosion rates of 91 m³ yr^–1 and 458 m³ yr^–1 respectively, and 220 m³ yr^–1 beachface accretion. Diminution of sediment supply observed over historical timescales was supported by decadal evidence. Here, profile analysis revealed a trend of decreasing volumes both updrift and within the study area, and increasing downdrift volumes. This explained why proximal detachment and sediment redistribution had occurred. Distinct reversal's in shoreline trend (rotation) corresponded to nearshore change; therefore, variations in seabed configuration triggered shoreface dynamic change over century timescales. Five‐year cumulative average changes in North Atlantic Oscillation were further correlated to this reversal. As comparable scenarios are likely to exist at other worldwide coastal locations, similar analyses should be incorporated into shoreline monitoring programmes. Consequently, these assessments would inform shoreline trends and support coastal management decisions. Copyright © 2011 John Wiley & Sons, Ltd.     

ArcIMS平台下图文资料管理系统的设计

对设计图文资料信息管理系统的设计和开发进行了研究,介绍了ArclMS和系统的体系结构,功能设计,数据库设计、特别是属性表的设计.     

徐州废黄河断裂带的空间展布与活动性研究

文中利用遥感影像分析了徐州废黄河断裂带的空间展布及与邵楼断裂的交切关系,利用重磁资料研究了废黄河断裂带的深部几何结构及与郯庐断裂带西边界的交切关系。二阶布格重力异常小波变换细节图反映出徐州废黄河断裂带的深度为7～8km,而三阶和四阶重力异常细节图反映的深度分别为9～11km和15～18km。研究结果表明,废黄河断裂带向SE延伸至九顶附近,向下的切割深度约为 8～9km。NW向的废黄河断裂带截切邵楼断裂致使邵楼断裂构造线自东北向西南由N60°E转至N45°E。废黄河断裂带与郯庐断裂带不相交。废黄河断裂带属于前第四纪断裂,活动性较弱。     

变化环境下武江超定量洪水门限值响应规律及影响

世界众多江河洪水超定量(POT)系列门限值已发生变化,门限值选取不当会影响频率分析合理性。结合历史洪水资料,采用洪水POT理论分析变化环境下武江门限值响应规律及影响。结果表明:武江流域下垫面植被和径流系数在1991年明显改变,变化环境下不仅洪水门限值显著增大,且超过特定量级洪水的发生次数也在增加,POT模型能捕捉洪水在量级和发生次数方面的变化信息。分别选用变化环境前后门限值来推算设计洪峰,当重现期大于200年时,坪石站差异度达19.21%,犁市站达8.12%以上。选用变化环境后高门限值可有效提高线型对大洪水的拟合程度和设计洪水计算精度。     

Track analysis and storm surge investigation of 2017 Typhoon Hato: were the warning signals issued in Macau and Hong Kong timed appropriately?

ABSTRACT

This study investigates the storm surge caused by Typhoon Hato, which severely affected Macau, Hong Kong, and other coastal cities in China on 23 August 2017. A typhoon and storm surge coupling model demonstrated that the maximum storm surge height reached nearly 2.5?m along the coast of Macau, while that in Hong Kong was slightly below 2?m. Furthermore, a field survey of urban flooding revealed evidence of a 2.25-m inundation in downtown Macau and a 0.55-m inundation on Lantau Island, Hong Kong, which were likely exacerbated by a combination of storm surge, heavy rainfall, and surface water runoff over a complex hilly terrain. Significant wave overtopping and runup also occurred in beach and port areas. A typhoon track analysis confirmed that several comparably strong typhoons have followed similar ESE to WNW trajectories and made landfall in the Pearl River Delta in the last few decades. Although Hato was not the strongest of these storms, its forward speed of about 32.5?km/h was remarkably faster than those of other comparable typhoons. Higher levels of storm signal warnings were issued earlier in Hong Kong than in Macau, raising questions about the appropriate timing of warnings in these two nearby areas. Our analysis of the storm’s pattern suggests that both regions’ decisions regarding signal issuance could be considered reasonable or at least cannot be simply blamed, given the rapid motion and intensification of Hato and the associated economic risks at stake.     

基于图幅的地形图数据自适应更新实现

随着城市建设的快速发展,城市基础地形图数据的更新与管理越来越受到城市规划部门和测绘部门的重视,地形图数据的自动化更新成为了一种迫切的需求。针对这一需求,在分析地形图数据特点的基础上,提出采用基于图幅更新的方式来保证地形图数据的现势性,详细地阐述了基于图幅更新的整个流程和历史数据回溯的过程,并开发了基于图幅更新的地形图数据自适应更新系统,同时以珠海市1:2 000地形图矢量数据为实例,验证了该方法的可行性。试验结果表明该方法能够很好地保证地形图数据的现势性。     

基于图幅的地形图数据自适应更新实现

随着城市建设的快速发展,城市基础地形图数据的更新与管理越来越受到城市规划部门和测绘部门的重视,地形图数据的自动化更新成为了一种迫切的需求。针对这一需求,在分析地形图数据特点的基础上,提出采用基于图幅更新的方式来保证地形图数据的现势性,详细地阐述了基于图幅更新的整个流程和历史数据回溯的过程,并开发了基于图幅更新的地形图数据自适应更新系统,同时以珠海市1：2000地形图矢量数据为实例,验证了该方法的可行性。试验结果表明该方法能够很好地保证地形图数据的现势性。