安徽省空间地理信息基础数据库示范工程研发

从工程组成及实现、关键技术及解决方法等方面,介绍和讨论已完成的“安徽省空间地理信息基础数据库示范工程”项目。示范库的建设工作达到了预期的目的。     

基于GIS和VRML技术的东圳水库3维仿真建模

以福建省莆田市东圳水库为例,讨论了基于VRML的水库及其周围地理环境、流域状况仿真建模过程,以及所采用的技术和方法。通过仿真系统可以直观分析水库的环境情况,水库管理者可在场景中漫游,从不同位置进行观察分析,进而提出相应解决措施。同时该系统作为对水库进行研究的人机交互平台,可进行实时完善和扩展。     

浅谈OpenGL在地学3维可视化中的应用

3维地形模型无论是在直观的视觉感受还是在空间分析等方面都是2维地学模型所无法比拟的。DEM是建立地学3维可视化的主要内容,也是3维地理信息系统GIS的主要研究内容之一。本文所实现的程序是在VC 6.0平台基础上,基于DEM数据,利用OpenGL提供的相关功能函数,达到地学3维可视化的目的,同时利用纹理映射技术为3维模型贴纹理建立真实感强的3维环境。     

浅析省级基础测绘数据在城市建模中的应用

利用基础测绘数据中房屋数据获取和编辑的方法,探讨1:10 000基础测绘数据中的建筑物在城市地理信息服务和建模中的应用以及目前基础测绘数据与城市建模数据间的差距.     

工程勘察数据的传递控制与可视化

从广义说,工程勘察成果中的很大一部分是通过大量数据的传递与处理取得的。数据传递结构的优化和合理控制是提高勘察效率和质量的保证。讨论了用程序编制的方法实现的数据从平面图到剖面图的钻孔距离传递,利用模糊聚类思想提出的对剖面数据进行合并的建议和利用地质三维软件实现的三维地质体模型的耦合展示,这几个问题正是目前大多勘察单位在数据控制与传递流程中可能欠缺的环节。     

三峡库区巫山县翠屏小区岩溶引起的地质灾害危险性研究

三峡库区移民迁建中发现的岩溶问题是一个重大工程地质问题。巫山县城翠屏小区是较早发现有确切岩溶证据的地方,研究证实小区三叠系嘉陵江组灰岩普遍遭受了强烈的岩溶作用。不同部位具有不同的岩溶特点和强度,在纵向上,从山顶到坡脚岩溶作用有增强的趋势;从地表向深部,有局部强烈岩溶层位。岩溶作用在小区产生了顺坡或顺层延伸的溶洞和深部蜂窝状溶孔。岩溶作用在小区形成了脖颈状溶蚀槽地、槽状谷地、溶蚀台地和与地貌相关的"飞雁状"褶皱、岩溶正断层及帚状密集节理带。岩溶过程中伴随着其他外营力作用,它们的相互耦合形成各种次生岩土体。岩溶轻则引起岩体质量降低,重则可能导致地面不均匀沉降、地裂缝、滑坡、崩塌、泥石流及地面塌陷地质灾害。     

Structural evolution of the Bayanhongor region, west-central Mongolia

Most of previous models suggest that the Central Asia Orogenic Belt grew southward in the Phanerozoic. However, in the Bayanhongor region in west-central Mongolia, volcanic arc, accretionary prism, ophiolite, and passive margin complexes accreted northeastward away from the Baydrag micro-continent, and hence the region constitutes the southwestern part of a crustal-scale syntaxis close to the west. The syntaxis should be original, because presumably reorientation due to strike-slip faulting can be ignored. It is reconfirmed that the Baydrag eventually collided with another micro-continent (the Hangai) to the northeast. A thick sedimentary basin developed along the southern passive margin of the Hangai micro-continent. This region is also characterized by an exhumed metamorphosed accretionary complex and a passive margin complex, which are both bounded by detachment faults as well as basal reverse faults which formed simultaneously as extrusion wedges. This part of the Central Asia Orogenic Belt lacks exhumed crystalline rocks as observed in the Himalayas and other major collisional orogenic belts. In addition, we identified two phases of deformation, which occurred at each phase of zonal accretion as D1 through Cambrian and Devonian, and a synchronous phase of final micro-continental collision of Devonian as D2. The pre-collisional ocean was wide enough to be characterized by a mid-ocean ridge and ocean islands. Two different structural trends of D1 and D2 are observed in accretionary complexes formed to the southwest of the late Cambrian mid-ocean ridge. That is, the relative plate motions on both sides of the mid-ocean ridge were different. Accretionary complexes and passive margin sediments to the northeast of the mid-ocean ridge also experienced two periods of deformation but show the same structural trend. Unmetamorphosed cover sediments on the accretionary prism and on the Hangai micro-continent experienced only the D2 event due to micro-continental collision. These unmetamorphosed sediments form the hanging walls of the detachment faults. Moreover, they were at least partly derived from an active volcanic arc formed at the margin of the Baydrag micro-continent.     

The Glueckstadt Graben of the North-German Basin: new insights into the structure from 3D and 2D gravity analyses

The structure of the Glueckstadt Graben has been investigated by use of 3D gravity backstripping technique and by 2D gravity and magnetic modelling. Subtracting the gravity effects of the Meso-Cenozoic sediments together with Permian salt reveals a positive residual anomaly within the Glueckstadt Graben. This anomaly includes two local maxima over the Westholstein and Eastholstein Troughs. The 2D gravity models point to the presence of a high-density body within the lower crust of the Glueckstadt Graben. In addition, the results of 2D magnetic modelling indicate that the central part of the high-density body is overlain by an area with high susceptibility. Most probable, the formation of this high-density body is a result of complex poly-phase tectonic history of the study area. Finally, the results of gravity modelling indicate that Permian salt is not homogeneous. 3D gravity analysis and, especially, 2D gravity modelling have distinguished the differences in degree of salt saturation in salt-rich bodies, and elucidate the proportion of Rotliegend salt.     

A virtual voyage through 3D structures generated by chaotic mixing of magmas and numerical simulations: a new approach for understanding spatial and temporal complexity of magma dynamics

In this contribution, we present a virtual voyage through 3D structures generated by chaotic mixing of magmas and numerical simulations with the aim to highlight the power of 3D representations in the understanding of this geological phenomenon. In particular, samples of mixed juveniles from Salina island (Southern Italy) are reconstructed in 3D by serial lapping and digital montage and numerical simulations are performed by using a 3D chaotic dynamical system. Natural and simulated magma mixing structures are visualized by using several multimedia tools including animations and “virtual reality” models. It is shown that magma interaction processes can generate large spatial and temporal compositional heterogeneities in magmatic systems. The same topological structures are observed in both 3D reconstructed rock samples and chaotic numerical simulations, indicating that the mixing of magmas is governed by chaotic dynamics. The use of 3D multimedia models gives the opportunity to penetrate into magma mixing structures and to understand their significance in the context of magma dynamics. Such an approach is very powerful since multimedia tools can strongly capture the attention of the reader bringing him/her into an interactive and memorable geological experience. Electronic supplementary material  enclosed:     

Comparison of numerical models of two debris flows in the Cortina d’ Ampezzo area,Dolomites, Italy

The accurate prediction of runout distances, velocities and the knowledge of flow rheology can reduce the casualties and property damage produced by debris flows, providing a means to delineate hazard areas, to estimate hazard intensities for input into risk studies and to provide parameters for the design of protective measures. The application of most of models that describe the propagation and deposition of debris flow requires detailed topography, rheological and hydrological data that are not always available for the debris-flow hazard delineation and estimation. In the Cortina d’Ampezzo area, Eastern Dolomites, Italy, most of the slope instabilities are represented by debris flows; 325 debris-flow prone watersheds have been mapped in the geomorphological hazard map of this area. We compared the results of simulations of two well-documented debris flows in the Cortina d’Ampezzo area, carried on with two different single-phase, non-Newtonian models, the one-dimensional DAN-W and the two-dimensional FLO-2D, to test the possibility to simulate the dynamic behaviour of a debris flow with a model using a limited range of input parameters. FLO-2D model creates a more accurate representation of the hazard area in terms of flooded area, but the results in terms of runout distances and deposits thickness are similar to DAN-W results. Using DAN-W, the most appropriate rheology to describe the debris-flow behaviour is the Voellmy model. When detailed topographical, rheological and hydrological data are not available, DAN-W, which requires less detailed data, is a valuable tool to predict debris-flow hazard. Parameters obtained through back-analysis with both models can be applied to predict hazard in other areas characterized by similar geology, morphology and climate.