KPAR:一个数值模糊的光学量

光合有效辐射(PAR)的漫衰减系数KPAR是水环境研究中经常使用的一个光学量.水体的漫衰减系数与波长紧密相关,随着水体深度的不断增加,PAR频谱收缩到具有更小衰减系数的波长处,对上层水体或者混合均匀的水体而言,此时的KPAR与水深关系极为密切.为了更为准确的描述PAR剖面,获取更可靠的光学衰减参数,强调了KPAR数值的模糊性,倡导正确表达KPAR的垂直变化.     

3D joint inversion of magnetotelluric and airborne tipper data: a case study from the Morrison porphyry Cu–Au–Mo deposit,British Columbia,Canada

Z‐axis tipper electromagnetic and broadband magnetotelluric data were used to determine three‐dimensional electrical resistivity models of the Morrison porphyry Cu–Au–Mo deposit in British Columbia. Z‐axis tipper electromagnetic data are collected with a helicopter, thus allowing rapid surveys with uniform spatial sampling. Ground‐based magnetotelluric surveys can achieve a greater exploration depth than Z‐axis tipper electromagnetic surveys, but data collection is slower and can be limited by difficult terrain. The airborne Z‐axis tipper electromagnetic tipper data and the ground magnetotelluric tipper data show good agreement at the Morrison deposit despite differences in the data collection method, spatial sampling, and collection date. Resistivity models derived from individual inversions of the Z‐axis tipper electromagnetic tipper data and magnetotelluric impedance data contain some similar features, but the Z‐axis tipper electromagnetic model appears to lack resolution below a depth of 1 km, and the magnetotelluric model suffers from non‐uniform and relatively sparse spatial sampling. The joint Z‐axis tipper electromagnetic inversion solves these issues by combining the dense spatial sampling of the airborne Z‐axis tipper electromagnetic technique and the deeper penetration of the lower frequency magnetotelluric data. The resulting joint resistivity model correlates well with the known geology and distribution of alteration at the Morrison deposit. Higher resistivity is associated with the potassic alteration zone and volcanic country rocks, whereas areas of lower resistivity agree with known faults and sedimentary units. The pyrite halo and ≥0.3% Cu zone have the moderate resistivity that is expected of disseminated sulphides. The joint Z‐axis tipper electromagnetic inversion provides an improved resistivity model by enhancing the lateral and depth resolution of resistivity features compared with the individual Z‐axis tipper electromagnetic and magnetotelluric inversions. This case study shows that a joint Z‐axis tipper electromagnetic–magnetotelluric approach effectively images the interpreted mineralised zone at the Morrison deposit and could be beneficial in exploration for disseminated sulphides at other porphyry deposits.     

Climate change and plague history in Europe

Previous research that reported the linkage between climate change and plague activity primarily refers to the immediate effect of short-term climatic variation. Yet, decades of discussion about the climate-plague association cannot determine the precise role of climate in shaping plague dynamics. One reason for this discrepancy originates from the narrow selection of spatio-temporal settings for comprehensive analysis of the correlation, leading to a limited consideration of the complexity of possible dynamics. By analyzing a 414-year long record of plague outbreak in pre-industrial Europe and the corresponding climatic data in multi-scale, we find little evidence to support climate-plague correlation in (1) both climatic variations and large-scale climatic phenomena, (2) both country scale and continental scale, (3) annual to inter-annual scale, and (4) both linear and non-linear analytic approaches. The null-result should not be viewed as a general rejection of other recent findings related to climate-plague association; nevertheless, it suggests that a wider consideration of scales, sensitivity checks and consideration of contexts should be included in explaining and predicting plague transmission under contemporary global climate conditions.     

Investigation of the dynamic behaviour of a storage tank with different foundation types focusing on the soil‐foundation‐structure interactions using centrifuge model tests

This paper proposes a dynamic centrifuge model test method for the accurate simulation of the behaviours of a liquid storage tank with different types of foundations during earthquakes. The method can be used to determine the actual stress conditions of a prototype storage‐tank structure. It was used in the present study to investigate the soil‐foundation‐structure interactions of a simplified storage tank under two different earthquake motions, which were simulated using a shaking table installed in a centrifuge basket. Three different types of foundations were considered, namely, a shallow foundation, a slab on the surface of the ground connected to piles and a slab with disconnected piles. The test results were organised to compare the ground surface and foundation motions, the slab of foundation and top of structure motions and the horizontal and vertical motions of the slab, respectively. These were used to establish the complex dynamic behaviours of tank models with different foundations. The effects of soil–foundation–structure interaction with three foundation conditions and two different earthquake motions are focused and some important factors, that should be considered for future designs are also discussed in this research. Copyright © 2017 John Wiley & Sons, Ltd.     

Concentrated, ‘pulsed’ axial glacier flow: structural glaciological evidence from Kvíárjökull in SE Iceland

A detailed structural glaciological study carried out on Kvíárjökull in SE Iceland reveals that recent flow within this maritime glacier is concentrated within a narrow corridor located along its central axis. This active corridor is responsible for feeding ice from the accumulation zone on the south‐eastern side of Öræfajökull to the lower reaches of the glacier and resulted in a c. 200 m advance during the winter of 2013–2014 and the formation of a push‐moraine. The corridor comprises a series of lobes linked by a laterally continuous zone of highly fractured ice characterised by prominent flow‐parallel crevasses, separated by shear zones. The lobes form highly crevassed topographic highs on the glacier surface and occur immediately down‐ice of marked constrictions caused by prominent bedrock outcrops located on the northern side of the glacier. Close to the frontal margin of Kvíárjökull, the southern side of the glacier is relatively smooth and pock‐marked by a number of large moulins. The boundary between this slow moving ice and the active corridor is marked by a number of ice flow‐parallel strike‐slip faults and a prominent dextral shear zone which resulted in the clockwise rotation and dissection of an ice‐cored esker exposed on the glacier surface. It is suggested that this concentrated style of glacier flow identified within Kvíárjökull has affinities with the individual flow units which operate within pulsing or surging glaciers. © 2017 The Authors Earth Surface Processes and Landforms © 2017 John Wiley & Sons, Ltd.     

Scenario Evaluator for Electrical Resistivity Survey Pre‐modeling Tool

Geophysical tools have much to offer users in environmental, water resource, and geotechnical fields; however, techniques such as electrical resistivity imaging (ERI) are often oversold and/or overinterpreted due to a lack of understanding of the limitations of the techniques, such as the appropriate depth intervals or resolution of the methods. The relationship between ERI data and resistivity is nonlinear; therefore, these limitations depend on site conditions and survey design and are best assessed through forward and inverse modeling exercises prior to field investigations. In this approach, proposed field surveys are first numerically simulated given the expected electrical properties of the site, and the resulting hypothetical data are then analyzed using inverse models. Performing ERI forward/inverse modeling, however, requires substantial expertise and can take many hours to implement. We present a new spreadsheet‐based tool, the Scenario Evaluator for Electrical Resistivity (SEER), which features a graphical user interface that allows users to manipulate a resistivity model and instantly view how that model would likely be interpreted by an ERI survey. The SEER tool is intended for use by those who wish to determine the value of including ERI to achieve project goals, and is designed to have broad utility in industry, teaching, and research.     

Degradation of crude oil in a contaminated tidal flat area and the resilience of bacterial community

Crude oil spills, Hebei Spirit in South Korea, is considered as one of the worst environmental disasters of the region. Our understanding on activation of oil-degrading bacteria and resilience of microbial community in oil contaminated sites are limited due to scarcity of such event. In the present study, tidal flat sediment contaminated by the oil spill were investigated for duration of 13 months to identify temporal change in microbial community and functional genes responsible for PAH-degradation. The results showed predominance of previously known oil-degrading genera, such as Cycloclasticus, Alcanivorax, and Thalassolituus, displaying significant increase within first four months of the accident. The disturbance caused by the oil spill altered the microbial community and its functional structures, but they were almost restored to the original state after 13 months. Present study demonstrated high detoxification capacity of indigenous bacterial populations in the tidal flat sediments and its resilience of microbial community.     

Permian felsic magmatism in the Neoproterozoic Nagar Parkar Igneous Complex of the Malani Igneous Suite: Evidence from zircon U–Pb age

We report Permian (ca. 272 Ma ±5.4 Ma) felsic dykes that intrude into the Neoproterozoic (ca. 750 Ma) magmatic suite of the Nagar Parkar Igneous Complex (NPIC), the western extension of the Malani Igneous Suite (MIS). The NPIC consists of Neoproterozoic basement amphibolites and granites (riebeckite–aegirine gray granites and the biotite–hornblende pink granites), all of which are intruded by several generations of mafic and felsic dykes. Granitic magmatism occurred in the Late Neoproterozoic (ca. 750 Ma) due to the subduction‐, followed by the rift‐related tectonic regime during the breakup of the Rodinia supercontinent. U–Th–Pb zircon and monazite CHIME age data of 700–800 Ma from the earlier generation porphyritic felsic dykes suggest the dyke intrusion was coeval or soon after the emplacement of the host granites. Our findings of Permian age orthophyric felsic dykes provide new insights for the prevalence of active tectonics in the MIS during late Paleozoic. Textural features and geochemistry also make the orthophyric dykes distinct from the early‐formed porphyritic dykes and the host granites. Our newly obtained age data combined with geochemistry, suggest the existence of magmatism along the western margin of India (peri‐Gondwana margin) during Permian. Like elsewhere in the region, the Permian magmatism in the NPIC could be associated with the rifting of the Cimmerian micro‐continents from the Gondwana.     

Scattering and reflection of SH waves around a slope on an elastic wedged space

The scattering and reflection of SH waves by a slope on an elastic wedged space is investigated. A series solution is obtained by using the wave function expansion method. The slope on a wedged space is divided into two subregions by an artificial, auxiliary circular arc. The wave fields with unknown complex coefficients within each sub-region are derived. Applying Graf addition theorem, the scattered waves in the sub-regions are expressed in a global coordinate system. Fourier transform is adopted to derive a consistent form of standing waves in the inner region using the orthogonality of the cosine functions. The boundary-valued problem is solved by stress and displacement continuity along the artificial, auxiliary arc to obtain the unknown complex coefficients. Parametric studies are next performed to investigate how the topography from the slope on the wedged space will affect the scattering and diffraction, and hence the amplification and de-amplification of the SH waves. Numerical results show that the surface motions on the slope of the wedged space is influenced greatly by the topography. Amplification of the surface motions near the slope vertex is significant. The corresponding phases along the wedged space surfaces are consistent with the direction that the SH waves are propagating.     

Energy correction of dynamic cone penetration index for reliable evaluation of shear strength in frozen sand–silt mixtures

Acta Geotechnica - Previously, in situ tests have been conducted in cold regions since infrastructures such as pipelines have been actively built on frozen ground. However, the engineering...