Geochemical variations in Andean basaltic and silicic lavas from the Villarrica-Lanin volcanic chain (39.5° S): an evaluation of source heterogeneity,fractional crystallization and crustal assimilation     

Rosemary Hickey -Vargas  Hugo Moreno Roa  Leopolde Lopez Escobar  Frederick A. Frey 《Contributions to Mineralogy and Petrology》1989,103(3):361-386

At 39.5° S in the southern volcanic zone of the Andes three Pleistocene-recent stratovolcanoes, Villarrica, Quetrupillan and Lanin, form a trend perpendicular to the strike of the Andes, 275 to 325 km from the Peru-Chile trench. Basalts from Villarrica and Lanin are geochemically distinct; the latter have higher incompatible element abundances and La/Sm but lower Ba/La and alkali metal/La ratios. These differences are consistent with our previously proposed models involving: a) a west to east decrease in an alkali metal-rich, high Ba/La slab-derived component which causes an across strike decrease in degree of melting; or b) a west to east increase in the contamination of subduction-related magma by enriched subcontinental lithospheric mantle. Silicic and mafic lavas from the stratovolcanoes have overlapping Sr, Nd and O isotopic ratios. Silicic lavas also have geochemical differences that parallel those of their associated basalts, e.g., rhyolite from Villarrica has lower La/Sm and incompatible element contents than high-SiO₂ andesite from Lanin. At each volcano the most silicic lavas can be modelled by closed system fractional crystallization while andesites are best explained by magma mixing. Apparently crustal contamination was not an important process in deriving the evolved lavas. Basaltic flows from small scoria cones, 20–35 km from Villarrica volcano have high incompatible element contents and low Ba/La, like Lanin basalts, but trend to higher K/Rb (356–855) and lower ⁸⁷Sr/ ⁸⁶Sr (0.70361–0.70400) than basalts from either stratovolcano. However all basalts have similar Nd, Pb and O isotope ratios. The best explanation for the unique features of the cones is that the sources of SVZ magmas, e.g., slab-derived fluids or melts of the subcontinental lithospheric mantle, have varying alkali metal and radiogenic Sr contents. These heterogeneities are not manifested in stratovolcano basalts because of extensive subcrustal pooling and mixing. This model is preferable to one involving crustal contamination because it can account for variable Sr isotope ratios and uniform Nd and Pb isotope ratios among the basalts, and the divergence of the cones from across-strike geochemical trends defined by the stratovolcanoes.  相似文献   

Propagation of positional error in 3D GIS: estimation of the solar irradiation of building roofs     

Filip Biljecki  Gerard B.M. Heuvelink  Hugo Ledoux  Jantien Stoter 《International journal of geographical information science》2013,27(12):2269-2294

While error propagation in GIS is a topic that has received a lot of attention, it has not been researched with 3D GIS data. We extend error propagation to 3D city models using a Monte Carlo simulation on a use case of annual solar irradiation estimation of building rooftops for assessing the efficiency of installing solar panels. Besides investigating the extension of the theory of error propagation in GIS from 2D to 3D, this paper presents the following contributions. We (1) introduce varying XY/Z accuracy levels of the geometry to reflect actual acquisition outcomes; (2) run experiments on multiple accuracy classes (121 in total); (3) implement an uncertainty engine for simulating acquisition positional errors to procedurally modelled (synthetic) buildings; (4) perform the uncertainty propagation analysis on multiple levels of detail (LODs); and (5) implement Solar3Dcity – a CityGML-compliant software for estimating the solar irradiation of roofs, which we use in our experiments. The results show that in the case of the city of Delft in the Netherlands, a 0.3/0.6 m positional uncertainty yields an error of 68 kWh/m²/year (10%) in solar irradiation estimation. Furthermore, the results indicate that the planar and vertical uncertainties have a different influence on the estimations, and that the results are comparable between LODs. In the experiments we use procedural models, implying that analyses are carried out in a controlled environment where results can be validated. Our uncertainty propagation method and the framework are applicable to other 3D GIS operations and/or use cases. We released Solar3Dcity as open-source software to support related research efforts in the future.  相似文献   

Automatic conversion of IFC datasets to geometrically and semantically correct CityGML LOD3 buildings   总被引：1，自引：0，他引：1       下载免费PDF全文

Sjors Donkers  Hugo Ledoux  Junqiao Zhao  Jantien Stoter 《Transactions in GIS》2016,20(4):547-569

Although the international standard CityGML has five levels of detail (LODs), the vast majority of available models are the coarse ones (up to LOD2, i.e. block‐shaped buildings with roofs). LOD3 and LOD4 models, which contain architectural details such as balconies, windows and rooms, rarely exist because, unlike coarser LODs, their construction requires several datasets that must be acquired with different technologies, and often extensive manual work is needed. In this article we investigate an alternative to obtaining CityGML LOD3 models: the automatic conversion from already existing architectural models (stored in the IFC format). Existing conversion algorithms mostly focus on the semantic mappings and convert all the geometries, which yields CityGML models having poor usability in practice (spatial analysis, for instance, is not possible). We present a conversion algorithm that accurately applies the correct semantics from IFC models and that constructs valid CityGML LOD3 buildings by performing a series of geometric operations in 3D. We have implemented our algorithm and we demonstrate its effectiveness with several real‐world datasets. We also propose specific improvements to both standards to foster their integration in the future.  相似文献   

Mid-Holocene lateral collapse of Antuco volcano (Chile): debris avalanche deposit features,emplacement dynamics,and impacts     

Romero  Jorge E.  Moreno  Hugo  Polacci  Margherita  Burton  Mike  Guzmán  Danny 《Landslides》2022,19(6):1321-1338

Antuco (37.4°S, 71.4°W; Chile) is a dominantly basaltic stratovolcano whose original?~?3300 m altitude main cone experienced a catastrophic sector collapse at?~?7.1 cal ka BP, producing a volcanic debris avalanche deposit (VDAD) with hummocky surface and?~?6.4 km³ of volume. We carried out geological studies of its debris avalanche deposit, which was distributed to the W and displays a longitudinal facies transformation from edifice’s megablocks and block to mixed facies in distal areas (up to 25 km from the scar). Our observations support the behavior of the avalanche beginning as a translational slide, and then as plug flow when confined within the Laja River valley. Clay abundance and high content of hydrothermally altered material may suggest active participation of water; flow velocities are estimated to?~100 m s^?1. We primarily identify the steep-sided flanks of the cone, and hydrothermal alteration promoted the edifice instability, while basement seismogenic structures may have ultimately triggered the landslide. Subsequent landslide-led events include the transformation of the volcanic activity with explosive eruptions producing a sequence of dilute pyroclastic density currents (PDCs) ending?~3.4 ky BP, and extensive lava effusion rapidly reconstructing the collapsed edifice. Moreover, the Antuco VDAD also blocked the natural output of the Laja Lake, increasing its level by?~200 m and then triggering cataclysmic outburst floods by dam rupture, preserved as high-energy alluvial beds with ages between 2.8 and 1.7 ky BP. The Antuco constitutes an excellent example of a critical chain of events initiated by a stratovolcano lateral collapse and warns for detailed hazard investigations to better comprehend its related impacts.

  相似文献   

Can climate variability information constrain a hydrological model for an ungauged Costa Rican catchment?          下载免费PDF全文

Beatriz Quesada‐Montano  Ida K. Westerberg  Diana Fuentes‐Andino  Hugo G. Hidalgo  Sven Halldin 《水文研究》2018,32(6):830-846

Long‐term hydrological data are key to understanding catchment behaviour and for decision making within water management and planning. Given the lack of observed data in many regions worldwide, such as Central America, hydrological models are an alternative for reproducing historical streamflow series. Additional types of information—to locally observed discharge—can be used to constrain model parameter uncertainty for ungauged catchments. Given the strong influence that climatic large‐scale processes exert on streamflow variability in the Central American region, we explored the use of climate variability knowledge as process constraints to constrain the simulated discharge uncertainty for a Costa Rican catchment, assumed to be ungauged. To reduce model uncertainty, we first rejected parameter relationships that disagreed with our understanding of the system. Then, based on this reduced parameter space, we applied the climate‐based process constraints at long‐term, inter‐annual, and intra‐annual timescales. In the first step, we reduced the initial number of parameters by 52%, and then, we further reduced the number of parameters by 3% with the climate constraints. Finally, we compared the climate‐based constraints with a constraint based on global maps of low‐flow statistics. This latter constraint proved to be more restrictive than those based on climate variability (further reducing the number of parameters by 66% compared with 3%). Even so, the climate‐based constraints rejected inconsistent model simulations that were not rejected by the low‐flow statistics constraint. When taken all together, the constraints produced constrained simulation uncertainty bands, and the median simulated discharge followed the observed time series to a similar level as an optimized model. All the constraints were found useful in constraining model uncertainty for an—assumed to be—ungauged basin. This shows that our method is promising for modelling long‐term flow data for ungauged catchments on the Pacific side of Central America and that similar methods can be developed for ungauged basins in other regions where climate variability exerts a strong control on streamflow variability.  相似文献   

Upward continuation of Dome-C airborne gravity and comparison with GOCE gradients at orbit altitude in east Antarctica     

Hasan Yildiz  Rene Forsberg  Carl Christian Tscherning  Daniel Steinhage  Graeme Eagles  Johannes Bouman 《Studia Geophysica et Geodaetica》2017,61(1):53-68

An airborne gravity campaign was carried out at the Dome-C survey area in East Antarctica between the 17th and 22nd of January 2013, in order to provide data for an experiment to validate GOCE satellite gravity gradients. After typical filtering for airborne gravity data, the cross-over error statistics for the few crossing points are 11.3 mGal root mean square (rms) error, corresponding to an rms line error of 8.0 mGal. This number is relatively large due to the rough flight conditions, short lines and field handling procedures used. Comparison of the airborne gravity data with GOCE RL4 spherical harmonic models confirmed the quality of the airborne data and that they contain more high-frequency signal than the global models. First, the airborne gravity data were upward continued to GOCE altitude to predict gravity gradients in the local North-East-Up reference frame. In this step, the least squares collocation using the ITGGRACE2010S field to degree and order 90 as reference field, which is subtracted from both the airborne gravity and GOCE gravity gradients, was applied. Then, the predicted gradients were rotated to the gradiometer reference frame using level 1 attitude quaternion data. The validation with the airborne gravity data was limited to the accurate gradient anomalies (T_XX, T_YY, T_ZZ and T_XZ) where the long-wavelength information of the GOCE gradients has been replaced with GOCO03s signal to avoid contamination with GOCE gradient errors at these wavelengths. The comparison shows standard deviations between the predicted and GOCE gradient anomalies T_XX, T_YY, T_ZZ and T_XZ of 9.9, 11.5, 11.6 and 10.4 mE, respectively. A more precise airborne gravity survey of the southern polar gap which is not observed by GOCE would thus provide gradient predictions at a better accuracy, complementing the GOCE coverage in this region.  相似文献   

Transportation mode-based segmentation and classification of movement trajectories     

Filip Biljecki  Hugo Ledoux  Peter van Oosterom 《International journal of geographical information science》2013,27(2):385-407

The knowledge of the transportation mode used by humans (e.g. bicycle, on foot, car and train) is critical for travel behaviour research, transport planning and traffic management. Nowadays, new technologies such as the Global Positioning System have replaced traditional survey methods (paper diaries, telephone) because they are more accurate and problems such as under reporting are avoided. However, although the movement data collected (timestamped positions in digital form) have generally high accuracy, they do not contain the transportation mode. We present in this article a new method for segmenting movement data into single-mode segments and for classifying them according to the transportation mode used. Our fully automatic method differs from previous attempts for five reasons: (1) it relies on fuzzy concepts found in expert systems, that is membership functions and certainty factors; (2) it uses OpenStreetMap data to help the segmentation and classification process; (3) we can distinguish between 10 transportation modes (including between tram, bus and car) and propose a hierarchy; (4) it handles data with signal shortages and noise, and other real-life situations; (5) in our implementation, there is a separation between the reasoning and the knowledge, so that users can easily modify the parameters used and add new transportation modes. We have implemented the method and tested it with a 17-million point data set collected in the Netherlands and elsewhere in Europe. The accuracy of the classification with the developed prototype, determined with the comparison of the classified results with the reference data derived from manual classification, is 91.6%.  相似文献   

Semi-empirical prediction method for monthly precipitation prediction based on environmental factors and comparison with stochastic and machine learning models     

Huihui Zhang  Hugo A. Loáiciga  Fu Ren  Da Ha 《水文科学杂志》2020,65(11):1928-1942

ABSTRACT

Precipitation prediction is central in hydrology and water resources planning and management. This paper introduces a semi-empirical predictive model to predict monthly precipitation and compares its predictive skill with those of machine learning (ML) methods. The stochastic method presented herein estimates monthly precipitation with one-step-ahead prediction properties. The ML predictive skill of the algorithms is evaluated by predicting monthly precipitation relying on the statistical association between precipitation and environmental and topographic factors. The semi-empirical predictive model features non-negative matrix factorization (NMF) for investigating the influence of multiple predictor variables on precipitation. The semi-empirical predictive model’s parameters are optimized with the hybrid genetic algorithm (GA) and Levenberg-Marquardt algorithm (LM), or GALMA, yielding a validated model with high predictive skill. The methodologies are illustrated with data from Hubei Province, China, which comprise 27 meteorological station datasets from 1988–2017. The empirical results provide valuable insights for developing semi-empirical rainfall prediction models.  相似文献   

Environmental Rationalism and Beyond: Toward a more just sharing of power and influence     

Graeme Aplin 《The Australian geographer》2000,31(3):273-287

Economics, especially the narrowly defined form of economics known as neo-liberal economics, along with its policy derivative known as economic rationalism, dominates public and political debate and decision-making in Australia and many other nations as the twentieth century approaches its close. In the context of environmental issues, as also in that of welfare issues, the present over-dominance is unhealthy. Despite the best attempts of environmental economists and ecological economists, they have had relatively little influence on the broader economic profession, or on the political and business communities. Economics and free trade also dominate the international scene at the expense of equity and environmental issues. Environmental debates, by their very nature, are usually complex, requiring interdisciplinary and multidisciplinary approaches which include the economic perspective, but much else besides. Despite the importance of local context and spatial and temporal location, there is a need for a meta-theory or national philosophy to allow the integration across space and time so often needed. The present meta-theory, firmly based in economic rationalism, is inadequate as a basis for environmental decision-making. We desperately need a new meta-theory that explicitly integrates economic, environmental, welfare and many other perspectives. Perhaps such a meta-theory could be broadly based on the concept of sustainability, though much more work is needed to refine such an approach. A major swing in public opinion from the old meta-theory to the new is essential as a forerunner to political action, and education at all levels is needed to bring about this change. There are some signs that this change is already informing public opinion, and that it may have begun to influence mainstream Australian politics.  相似文献   

Structural analysis of dyke emplacement directions as an aid to palaeomagnetic studies: an example from northern Chile     

Graeme Taylor  & Darren Randall 《Geophysical Journal International》2000,141(1):252-258

A major problem in palaeomagnetic studies of intrusive rocks lies in determining whether or not such rocks have been subjected to post-emplacement tilting. Structural analysis of dyke emplacement directions can be used to show the current attitude of the extension direction for the dyke swarm. If the original extension direction, at the time of emplacement, can be deduced from geological evidence, this then provides a field test for post-emplacement tilting of the dyke swarm and its host rocks. In the example given from northern Chile, we were able to make a palaeomagnetic study of and structurally analyse three successively younger dyke swarms that intrude similarly younging plutons. All three dyke swarms yielded extension directions close to horizontal but with markedly different azimuths. It is argued that the similarity in the plunge of the extension directions cannot be coincidental and that the dykes and their host plutons have not suffered significant post-emplacement tilting. This simple technique should be widely applicable in the assessment of post-emplacement tilting of dykes in palaeomagnetic studies.  相似文献