Beiträge zur Geochemie     

R. Ed. Liesegang 《International Journal of Earth Sciences》1913,4(5-6):404-408

Ohne Zusammenfassung  相似文献   

Begriff und Bedeutung der Intrusionstektonik     

Franz Ed. Suess 《International Journal of Earth Sciences》1927,18(2):149-154

Ohne Zusammenfassung  相似文献   

Properties of hot stars in the Wolf--Rayet galaxy NGC 5253 from ISO-SWS spectroscopy     

Paul A. Crowther  S. C. Beck  Allan J. Willis  Peter S. Conti  Patrick W. Morris  Ralph S. Sutherland 《Monthly notices of the Royal Astronomical Society》1999,304(3):654-668

  相似文献   

Petrophysics and mineral exploration: a workflow for data analysis and a new interpretation framework     

Michael Dentith  Randolph J. Enkin  William Morris  Cameron Adams  Barry Bourne 《Geophysical Prospecting》2020,68(1):178-199

As mineral exploration seeks deeper targets, there will be a greater reliance on geophysical data and a better understanding of the geological meaning of the responses will be required, and this must be achieved with less geological control from drilling. Also, exploring based on the mineral system concept requires particular understanding of geophysical responses associated with altered rocks. Where petrophysical datasets of adequate sample size and measurement quality are available, physical properties show complex variations, reflecting the combined effects of various geological processes. Large datasets, analysed as populations, are required to understand the variations. We recommend the display of petrophysical data as frequency histograms because the nature of the data distribution is easily seen with this form of display. A petrophysical dataset commonly contains a combination of overlapping sub-populations, influenced by different geological factors. To understand the geological controls on physical properties in hard rock environments, it is necessary to analyse the petrophysical data not only in terms of the properties of different rock types. It is also necessary to consider the effects of processes such as alteration, weathering, metamorphism and strain, and variables such as porosity and stratigraphy. To address this complexity requires that much more supporting geological information be acquired than in current practice. The widespread availability of field portable instruments means quantitative geochemical and mineralogical data can now be readily acquired, making it unnecessary to rely primarily on categorical rock classification schemes. The petrophysical data can be combined with geochemical, petrological and mineralogical data to derive explanations for observed physical property variations based not only on rigorous rock classification methods, but also in combination with quantitative estimates of alteration and weathering. To understand how geological processes will affect different physical properties, it is useful to define three end-member forms of behaviour. Bulk behaviour depends on the physical properties of the dominant mineral components. Density and, to a lesser extent, seismic velocity show such behaviour. Grain and texture behaviour occur when minor components of the rock are the dominate controls on its physical properties. Grain size and shape control grain properties, and for texture properties the relative positions of these grains are also important. Magnetic and electrical properties behave in this fashion. Thinking in terms of how geological processes change the key characteristics of the major and minor mineralogical components allows the resulting changes in physical properties to be understood and anticipated.  相似文献   

A worldwide correlation for exponential bed particle size variation in subaerial aqueous flows     

P. H. Morris  D. J. Williams 《地球表面变化过程与地形》1999,24(9):835-847

The particle size of the bed sediments in or on many natural streams, alluvial fans, laboratory flumes, irrigation canals and mine waste deltas varies exponentially with distance along the stream. A plot of the available worldwide exponential bed particle size diminution coefficient data against stream length is presented which shows that all the data lie within a single narrow band extending over virtually the whole range of stream lengths and bed sediment particle sizes found on Earth. This correlation applies to both natural and artificial flows with both sand and gravel beds, irrespective of either the solids concentration or whether normal or reverse sorting occurs. This strongly suggests that there are common mechanisms underlying the exponential diminution of bed particles in subaerial aqueous flows of all kinds. Thus existing models of sorting and abrasion applicable to some such flows may be applicable to others. A comparison of exponential laboratory abrasion and field diminution coefficients suggests that abrasion is unlikely to be significant in gravel and sand bed streams shorter than about 10 km to 100 km, and about 500 km, respectively. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Scattered ground‐roll attenuation using model‐driven interferometry          下载免费PDF全文

Phil Bilsby  Lee West  Ed Kragh  John Quigley 《Geophysical Prospecting》2015,63(1):116-132

Scattered ground roll is a type of noise observed in land seismic data that can be particularly difficult to suppress. Typically, this type of noise cannot be removed using conventional velocity‐based filters. In this paper, we discuss a model‐driven form of seismic interferometry that allows suppression of scattered ground‐roll noise in land seismic data. The conventional cross‐correlate and stack interferometry approach results in scattered noise estimates between two receiver locations (i.e. as if one of the receivers had been replaced by a source). For noise suppression, this requires that each source we wish to attenuate the noise from is co‐located with a receiver. The model‐driven form differs, as the use of a simple model in place of one of the inputs for interferometry allows the scattered noise estimate to be made between a source and a receiver. This allows the method to be more flexible, as co‐location of sources and receivers is not required, and the method can be applied to data sets with a variety of different acquisition geometries. A simple plane‐wave model is used, allowing the method to remain relatively data driven, with weighting factors for the plane waves determined using a least‐squares solution. Using a number of both synthetic and real two‐dimensional (2D) and three‐dimensional (3D) land seismic data sets, we show that this model‐driven approach provides effective results, allowing suppression of scattered ground‐roll noise without having an adverse effect on the underlying signal.  相似文献   

Complexities in hindcasting models--when should we say enough is enough     

Maslia ML  Aral MM  Faye RE  Grayman WM  Suárez-Soto RJ  Sautner JB  Anderson BA  Bove FJ  Ruckart PZ  Moore SM 《Ground water》2012,50(1):10-6; discussion 16-8

  相似文献   

Uncertainty estimation for operational ocean forecast products—a multi-model ensemble for the North Sea and the Baltic Sea     

Inga Golbeck  Xin Li  Frank Janssen  Thorger Brüning  Jacob W. Nielsen  Vibeke Huess  Johan Söderkvist  Bjarne Büchmann  Simo-Matti Siiriä  Olga Vähä-Piikkiö  Bruce Hackett  Nils M. Kristensen  Harald Engedahl  Ed Blockley  Alistair Sellar  Priidik Lagemaa  Jose Ozer  Sebastien Legrand  Patrik Ljungemyr  Lars Axell 《Ocean Dynamics》2015,65(12):1603-1631

  相似文献   

Successional changes in soil and hyporheic nitrogen fertility on an alluvial flood plain: implications for riparian vegetation     

Michael R. Morris  Brook O. Brouwer  Jeremy K. Caves  Mary J. Harner  Jack A. Stanford 《Aquatic Sciences - Research Across Boundaries》2010,72(4):519-532

In floodplain primary succession, vegetation colonizes nitrogen-poor alluvial deposits and fertility improves as soil nitrogen accumulates over time. It is generally assumed that vegetation assimilates the vast majority of its nitrogen from the soil; however, recent studies have suggested that the hyporheic zone also may be an important nitrogen source. We investigated the potential relative importance of hyporheic nitrogen by comparing fertility indices, specifically total (TN), dissolved inorganic (DIN), potentially mineralizable (PMN) and ion exchange resin nitrogen (IERN) in both soils and the hyporheic zone at early, mid and late succession stands on an expansive river flood plain. We also constructed mesocosms to assess growth of cottonwood cuttings with access to soil and/or hyporheic water. We found TN and PMN increased from early to mid succession in both the soil (to 10 cm) and hyporheic zone (in a 10 cm layer). While TN, DIN and PMN were an order of magnitude higher in the soil than in the hyporheic zone, IERN was higher in the hyporheic zone, indicating that subsurface flow through the flood plain may be important in delivering nitrogen to the root zone. However, even when flux was added to the hyporheic PMN pool, nitrogen availability in the hyporheic zone (in a 10 cm layer) was vastly lower than soil PMN (to 10 cm). Further, the instantaneous standing stock of DIN in the surface soil alone was about equal to the sum of the DIN pool, the mean subsurface flux and the PMN pool in a 10 cm layer of hyporheic zone. In the mesocosm experiment, cottonwood cuttings with access to both soil and hyporheic water grew fastest; however, they also had the lowest foliar nitrogen concentrations, indicating that this was not due to greater nitrogen availability. In the field, nitrogen content of cottonwood foliage increased along with soil (but potentially hyporheic as well) nitrogen accumulation during succession, suggesting the vegetation responded to increasing nitrogen fertility. We conclude that at least on a per unit-volume basis, the hyporheic zone probably provides little nitrogen relative to the surface soil, except on new alluvial bars that characteristically are nitrogen poor. Therefore, the hyporheic zone is probably a much smaller nitrogen source for mature forests relative to the surface soil unless the vegetation exploits a much larger volume of the hyporheic zone than surface soil.  相似文献   

Residual drift demands in moment‐resisting steel frames subjected to narrow‐band earthquake ground motions     

Edén Bojórquez  Jorge Ruiz‐García 《地震工程与结构动力学》2013,42(11):1583-1598

This paper presents the main results of the evaluation of residual inter‐story drift demands in typical moment‐resisting steel buildings designed accordingly to the Mexican design practice when subjected to narrow‐band earthquake ground motions. Analytical 2D‐framed models representative of the study‐case buildings were subjected to a set of 30 narrow‐band earthquake ground motions recorded on stations placed in soft‐soil sites of Mexico City, where most significant structural damage was found in buildings as a consequence of the 1985 Michoacan earthquake, and scaled to reach several levels of intensity to perform incremental dynamic analyses. Thus, results were statistically processed to obtain hazard curves of peak (maximum) and residual drift demands for each frame model. It is shown that the study‐case frames might exhibit maximum residual inter‐story drift demands in excess of 0.5%, which is perceptible for building's occupants and could cause human discomfort, for a mean annual rate of exceedance associated to peak inter‐story drift demands of about 3%, which is the limiting drift to avoid collapse prescribed in the 2004 Mexico City Seismic Design Provisions. The influence of a member's post‐yield stiffness ratio and material overstrength in the evaluation of maximum residual inter‐story drift demands is also discussed. Finally, this study introduces response transformation factors, T_p, that allow establishing residual drift limits compatible with the same mean annual rate of exceedance of peak inter‐story drift limits for future seismic design/evaluation criteria that take into account both drift demands for assessing a building's seismic performance. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献