The significance of morphometric analysis for obtaining groundwater potential zones in a structurally controlled terrain

Watershed development and management plans are more important for harnessing surface water and groundwater resources in arid and semi-arid regions. To prepare a comprehensive watershed development plan, it becomes necessary to understand the topography, erosion status and drainage patterns of the region. This study was undertaken to determine the drainage characteristics of Pageru River basin using topographical maps on a scale of 1:50,000. The total area of the Pageru River basin is 480 km². It was divided into X sub-basins for analysis. The drainage patterns of the basin are dendritic and include a sixth order stream. The quantitative analysis of various aspects of a river basin drainage network characteristics reveals complex morphometric attributes. The streams of lower orders mostly dominate the basin. The development of stream segments in the basin area is more or less affected by rainfall. The elongated shape of the basin is mainly due to the guiding effect of thrusting and faulting. The erosional processes of fluvial origin have been predominately influenced by the subsurface lithology of the basin.     

Remote sensing and geomorphometry for studying relief production in high mountains

Mountain topography is the result of highly scale-dependent interactions involving climatic, tectonic, and surface processes. No complete understanding of the geodynamics of mountain building and topographic evolution yet exists, although numerous conceptual and physical models indicate that surficial erosion plays a significant role. Mapping and assessing landforms and erosion in mountain environments is essential in order to understand landscape denudation and complex feedback mechanisms. This requires the development and evaluation of new approaches in remote sensing and geomorphometry. The research herein evaluates the problem of topographic normalization of satellite imagery and demonstrates the use of terrain analysis using a digital elevation model (DEM) to evaluate the relief structure of the landscape in the western Himalaya. We specifically evaluated the Cosine-correction and Minnaert-correction methods to reduce spectral variation in imagery caused by the topography. Semivariogram analyses of the topography were used to examine the relationships between relief and surface processes. Remote-sensing results indicate that the Minnaert-correction method can be used to reduce the “topographic effect” in satellite imagery for mapping, although extreme radiance values are the result of not accounting for the diffuse-skylight and adjacent-terrain irradiance. Geomorphometry results indicate that river incision and glaciation can generate extreme relief, although the greatest mesoscale relief is produced by glaciation at high altitudes. At intermediate altitudes, warm-based glaciation was found to decrease relief. Our results indicate that glaciation can have a differential influence on the relief structure of the landscape. Collectively, our results indicate that scale-dependent analysis of the topography is required to address radiation transfer issues and the polygenetic nature of landscape denudation and relief production.     

Spatial spillover and the factors influencing public service supply in Sichuan province,China

This article examines the spatial characteristics of public service supply and the factors influencing such supply in cities of Sichuan Province, China using spatial-autocorrelation and spatial econometric models with statistical data in 2012. The results demonstrate that expenditures on different types of public services present different spatial autocorrelation patterns. Although the spatial differences in basic public service expenditures are relatively small, a clear fan-shaped spillover to the east can be seen in Chengdu City. Chengdu also shows high clustering of advanced public service expenditures, being a typical core-periphery pattern. Post-earthquake reconstruction expenditures are clustered in the ＂5.12 Wenchuan earthquake＂ region and spill over toward cities to the east. The efficiency of public services in the mountainous areas in western Sichuan is low and exhibits a pattern of low-low spatial autocorrelation. The efficiency of public service supply is affected by economic, social, political and geographical factors. Based on the results of this analysis, we recommend a supply strategy that incorporates different types of public services and a specialized public service supply strategy for mountainous areas. Overall public service efficiency should be enhanced by focusing on narrowing the gap in farmers＇ income among regions and accelerating urbanization. Decision-makers should consider moresupportive policies with regard to providing basic public services in mountainous areas to ensure an equalized supply of basic public services. To enhance the efficiency of advanced public service supply, additional growth pole should be encouraged and incentivized; however, investments are required to drive the development of the peripheral regions through regional economic integration. Both software and hardware types of infrastructure are required to supply services efficiently during post-disaster reconstruction.     

用VB在AutoCAD中绘制地形图程序开发

介绍了在Visual Basic Language(VB)程序设计语言基础上启动AutoCAD绘制地形图的方法,编写了使用VB通过全站仪导出数据在AutoCAD中绘图的绘图程序。     

The Cookie Cutter: A method for obtaining a quantitative 3D description of glacial bedforms

Recording the position and attributes of subglacial bedforms, particularly drumlins, is paramount in determining the extent, and dynamics, of former ice sheets. This paper presents a method of deriving 3D properties of glacier bedforms (drumlins in this case) in order to quantify bedform dimensions and acquire information necessary for further investigations, such as calculating amounts of sediment moved subglacially and hence interactions between a glacier and a deformable bed. The method developed here is a semi-automated technique, called Cookie Cutter after the baking implement/process. This method is applied to 5 m spatial resolution DEM data and is based on manual geomorphological mapping of the DEM images, which forms the judgmental part of the process. The mapped bedforms are then processed individually using an automated technique which is described in detail with worked examples from western Central Scotland, which was last glaciated during the Last Glacial Maximum and the Younger Dryas. The advantages and potential sources of error are discussed and results from the sample area are used to compare the volumes of drumlins in an area of LGM glaciation with those in an area glaciated during the Younger Dryas.     

阿尔金南缘塔特勒克布拉克花岗岩的地球化学特征、锆石U-Pb定年及Hf同位素组成

地球化学研究显示,阿尔金造山带南缘瓦石峡河附近塔特勒克布拉克二长花岗岩具有高硅(SiO2=63.62%～72.06%)、高碱(ALK=6.39～7.83)、过铝质(ASI=1.27～1.43)的特征,其稀土元素含量中等,Eu负异常较明显,轻稀土相对富集;在原始地幔标准化蛛网图上,大部分样品相对富集LREE、Rb、Th、U等大离子亲石元素,亏损Nb、Ta、Sr、P、Ti等高场强元素,指示其为壳源型高钾钙碱性系列的强过铝质S型花岗岩。锆石Hf同位素研究结果表明,其εHf(t)=-9.1～-10.5,两阶段Hf同位素模式年龄tDMC为1457～1553Ma,反映该花岗岩的源岩主要来自于地壳物质的重熔,其来源也相对单一。岩石中Nb/Ta、Zr/Hf、Th/U比值及高的CaO/Na2O比值(0.3),高的Al2O3、CaO和FeOT+MgO+TiO2总量,暗示该花岗岩是由中下地壳的杂砂岩经过黑云母脱水熔融形成的。较低的Al2O3/TiO2比值以及高的Y和Yb含量表明,该花岗岩的源岩是在较高的温度及较低的压力条件下部分熔融产生的,熔融的残留相可能为斜长角闪岩。阴极发光图像显示,该岩石中的锆石呈自形的长柱状,具有明显的岩浆环带结构,LA-ICP-MS微区原位U-Pb定年获得462±2Ma一组年龄,结合阴极发光图像和锆石微量元素特征(Th/U0.1),推断该年龄值为花岗岩的形成年龄。根据CaO/Na2O-Al2O3/TiO2图解和R1-R2构造判别图解,确定该花岗岩可能形成于碰撞造山后抬升初期。对比花岗岩形成年龄(462Ma)与阿尔金造山带南缘已获得的高压-超高压岩石变质年龄(～500Ma),可推断阿尔金瓦石峡南二长花岗岩形成于阿尔金造山带俯冲碰撞造山后应力释放的初级阶段,在该阶段地壳物质由于压力的降低从而发生部分熔融。     

Compound[ing] disasters in Puerto Rico: Pathways for virtual transdisciplinary collaboration to enhance community resilience

Puerto Rico has been subject to complex and compounding effects of multiple disasters, exacerbated by sociopolitical, climactic, and geographical challenges that complicate relief and resilience. Interdisciplinary teams are uniquely suited to traverse emerging challenges in post-disaster settings, but there are few studies that leverage transdisciplinary skill sets and virtual co-production of knowledge to build on local autonomous responses. Communities are key sources of information and innovation which can serve as a model for recovery amidst disaster. Thus, an interdisciplinary team of emerging scholars collaborated with Caras con Causa, a local organization in Cataño, Puerto Rico, to develop processes for enhancing autonomous responses to disaster events through participatory pathways, specifically highlighting local knowledge and preferences. The results of this collaboration include: (1) an iterative process model for transdisciplinary co-production in virtual settings and (2) key highlights from post engagement reflections including community-scale definitions of disaster, and limitations to virtual collaboration amidst disaster. Together, these results yielded critical insights and lessons learned, including recommendations for improved project communication methods within transdisciplinary and virtual collaborations. Collectively, the process, it’s resulting products, and the post-engagement reflections demonstrate a pathway for scholars and community members to engage disaster resilience challenges. These strategies are most effectively practiced through focused collaboration with community stakeholders and are paramount in solving real-world challenges related to the increasing complex of compounding disasters.     

Inversion of relief on Mars

Relief inversion has been invoked to explain a number of geomorphic features of the martian surface. Terrestrial relief inversion occurs when former depressions become elevated because their fill is more resistant to erosion than the surrounding terrain. It is a common product of long-term landscape evolution on Earth, especially in relatively stable intra-cratonic settings and flat, or near flat lying successions. The inverted relief will preserve relicts of former land surfaces and is therefore older than the surrounding terrain. Relief inversion can occur by a range of processes, including infill of depressions by intrinsically resistant material, selective secondary cementation via diagenesis and weathering, or surface armouring. We examine a number of possible cases of inverted relief on Mars that appear to have formed by these three processes. We suggest that the most likely cementing agents for surface induration are iron oxides, silica, and sulfates. Possible cementation mechanisms include fluid mixing during regional groundwater flow, cooling of hydrothermal or basinal fluids as they near the surface, and evaporation and sublimation of near surface water. Wind action appears the most common erosive process on Mars capable of the regional landscape lowering necessary for relief inversion to occur, unlike on Earth where both deflation and runoff are important. Preliminary crater densities of selected features show that the tops of the proposed inverted relief have considerably more craters than the surrounding plains, as is predicted by the inversion hypothesis. More accurate dating of inverted surfaces and the adjacent areas may provide a simple way of measuring the degree of erosion over time in at least some areas of Mars.     

华北平原区地温梯度与基底构造形态的关系

本文根据部分实测温度资料和有限单元法的数值模拟计算结果,研究了华北平原区地温梯度和地表热流值与基底构造形态的关系,分析了盖层相对厚度、基岩侧界面倾角以及不同岩石热导率比值对地温梯度和地表热流分布图式的影响,并讨论了地壳浅部热流的折射和再分配问题。在此基础上,提出了华北平原区地温梯度和热流值基底构造形态的相关直线校正法,即根据不同构造部位上钻孔的实测地温梯度和盖层相对厚度的相关直线推算区域平均地温梯度和具代表性区域热流值的方法。     

地形起伏度最佳分析区域预测模型

地形起伏度指分析区域内最高点和最低点之差,反映宏观区域内地形的起伏特征,是描述地貌形态的定量指标。确定最佳分析区域是地形起伏度提取算法的核心步骤,以及决定地形起伏度提取结果有效性的关键。本文以全国范围内随机选取的78个实验区域、三种不同尺度的DEM数据作为实验对象,分别进行系列分析区域尺度的地形起伏度计算,建立了基于微观地形特征因子的地形起伏度最佳分析区域预测模型。实验表明：相同区域、不同尺度的DEM数据提取的地形起伏度存在差异,DEM尺度相差较小时,地形起伏度的差异也较小;地形起伏度和实验区域的最大高程、区域高差、平均坡度和平均坡度变率等地形特征因子存在强相关关系;当置信水平为0.05时,预测模型拟合参数的准确率达到95%以上,证明预测模型可以有效地确定最佳分析区域的取值范围。