Land subsidence in China

Land subsidence in China occurs in different regions. It is primarily caused by excessive groundwater withdrawal. Other reasons for the subsidence include the oil, warm groundwater withdrawal and the neotectonic movement. The common characteristics of land subsidence in China are slow, accumulative, irreversible, and other unique properties. The range of subsidence still keeps extending and the accumulative subsidence increasing though some measures taken. Adjustment of the aquifer exploitation practice is a subsidiary way to control land subsidence, but it cannot solve this problem completely. In a specfic way of groundwater changing, the contribution of a certain soil layer to the total subsidence depends on its compressibility and thickness. Besides the elasticity, both cohesive soil layers (aquitards) and sand layers (aquifers) are observed to be plastic and creep when the groundwater level fluctuates in a specific way, which often leads to subsidence delay.     

Study on Short-Term Abnormal Characteristics of Geoelectric and Geomagnetic Data before Strong Earthquakes in the North China Region

INTRODUCTIONStrongearthquakeactivityrepresentsalarge scalecrustaltectonicmovementprocess .Intheprocessofearthquakepreparation ,thedistributionofthegeophysicalparametersintheearthquakepreparationareahasthecharacteroftemporalcontinuityandspatialdependencewithdifferentgeologicalstructures ,andhenceaseismicprecursoryfieldisformed .Affectedbythetectonicstressfieldandthestressfieldinthefocalarea ,theearthresistivityinthesourceanditssurroundingareaswillchangeintheprocessofearthquakepreparation .…     

NASA地球科学事业（ESE）计划中的科学问题

作为NASA地球科学事业（ESE）分计划之一的ESE研究战略，在未来10年中，将主要关注以下 5个科学问题：①全球地球系统是怎样变化的？②地球系统的主要驱动力是什么？③地球系统如何响应自然和人为引起的变化？④地球系统的变化对人类文明造成的后果是什么？⑤如何更好地预测地球系统未来的变化？这 5个问题都是大范围的跨学科问题，涉及到地球系统科学的各个方面。在这 5个大的科学问题之下，又具体细化为23个二级问题，并对这些问题 进行了极其详尽的讨论。     

Ground cracks in Ethiopian Rift Valley: facts and uncertainties

No accurate relationship has been obtained in this study between ground cracks in Ethiopian Rift Valley and the most common causes of earth fissures such as aquifer-system compaction and increased horizontal seepage stresses. This is due to the fact that the level of groundwater withdrawal responsible for these processes is still negligible in Ethiopia. If aquifer-system compaction and increased horizontal seepage stresses have a certain role, then it should be through the long-term effect of groundwater flow from basins to neighboring lakes. The ground cracks appeared also not to have a direct link with active faulting or distant earthquakes. Structurally, the Ethiopian Rift Valley is dominated by NE–SW-trending tensional faults, but no evidence is obtained in this study to associate the process of surface cracking with major tectonics. However, an aseismic elastic strain, which originates at depth and propagates upward through sediments without the formation of bedrock faults, could result in conditions conducive to the development of cracks. Then, fissures might ultimately be created after heavy rainfalls by near-surface processes such as piping and hydrocompaction along water-line sources.     

无连接挡板高填方路堤薄壁挡土墙土压力模型试验研究

提出了一种新型的互锚薄壁挡土墙,该挡土墙是在传统加筋土墙的基础上发展起来的。以钢筋为拉筋,两侧的挡土墙面板通过拉筋对称连接互锚。通过模型试验测试了该结构挡土墙面板后土压力的分布规律。挡土面板后土压力并不是呈线性分布,也没有表现中间大、两端小的三角形分布或曲线,即在挡土墙的墙底和墙顶土压力接近于0、在挡土墙的中间土压力最大的分布规律,而是在距离挡土墙顶部1/3h以上(h为墙高),挡土墙面板后的土压力分布完全呈线性分布,与朗肯主动土压力理论相似;但是在距离挡土墙顶部1/3h以下位置,挡土墙面板后的土压力随着挡土墙高度的延伸,土压力基本保持不变,近似呈现一条竖线段。结果表明这种挡土墙的承栽能力得到明显加强。     

北京国家地球观象台的管理

指出了北京国家地球观象台目前存在的一些问题,分析了出现这些问题的原因,并运用现代管理学的观点论述了解决这些问题的思路和方法。提出了把北京国家地球观象台建成监测、预测、科研三结合台站的管理目标,给出了实现这个目标应采取的管理方法和必要措施。     

空间对地观测与全球变化的人文因素

地球空间信息科学技术是大有作为的科技领域之一。空间遥感、地理信息系统、卫星定位及其与通信、网络技术的集成正以地球系统作为研究对象，为人们研究地球，特别是人与自然的和谐、人口资源环境的协调和社会的可持续发展提供了前所未有的手段，开拓了崭新的途径。在对国际空间遥感信息技术和空间信息的特点和发展趋势进行科学判断的基础上，分析了对地观测与人文因素的关系，提出了建立国家对地观测系统，发展空间信息技术的战略设想。     

磁偏角磁变仪的定向

分析了影响磁偏角磁变仪定向质量的原因，指出应重视阻尼器影响，提出磁偏角磁变仪以在实际工作环境中定向最佳，用扭头带动镜面法定向实用性强，无须做任何改正。     

地气.地光.地象

在地壳运动释出物质和能量改变低层大气物理化学状态中的一个重要的方面就是增大大气中的体电荷，改变大气离子浓度，强化大气静电场，人类经历的许多自然灾异现象都含有地壳运动的信息，用这些现象的时空分布反演现代地壳运动微观状态是解决人类面临的地震及一系灾异成因研究预测预防的可行之路。