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961.
962.
R. M. Wooten K. A. Gillon A. C. Witt R. S. Latham T. J. Douglas J. B. Bauer S. J. Fuemmeler L. G. Lee 《Landslides》2008,5(1):31-44
In September 2004, rain from the remnants of Hurricanes Frances and Ivan triggered at least 155 landslides in the Blue Ridge
Mountains of North Carolina. At least 33 debris flows occurred in Macon County, causing 5 deaths, destroying 16 homes, and
damaging infrastructure. We mapped debris flows and debris deposits using a light-detecting and ranging digital elevation
model, remote imagery and field studies integrated in a geographic information system. Evidence of past debris flows was found
at all recent debris flow sites. Orographic rainfall enhancement along topographic escarpments influenced debris flow frequency
at higher elevations. A possible trigger for the Wayah and fatal Peeks Creek debris flows was a spiral rain band within Ivan
that moved across the area with short duration rainfall rates of 150–230 mm/h. Intersecting bedrock structures in polydeformed
metamorphic rock influence the formation of catchments within structural–geomorphic domains where debris flows originate. 相似文献
963.
Huiwei Chen Mee Kam Ng Murat Es Joanna Lee Winnie W. S. Mak Yuying Tong 《Urban geography》2018,39(7):969-987
This paper draws on theoretical discussions of world cities to analyze socio-spatial polarization and (re-)distribution of deprived groups in Hong Kong in the 2000s. Intensifying global economic restructuring processes have induced socio-economic polarization, thereby producing deprived groups although the spatial outcomes may depend on the city-specific context. When local policies do not counteract the polarization trend, a spatial manifestation of widening socio-economic gaps can be expected. Intensified pro-growth policies adopted since Hong Kong’s return to Chinese rule in 1997 and during its economic recession in the early 2000s have worsened the impact of globalization-induced socio-economic and spatial restructuring. Census data from 2001 and 2011 show increasingly differentiated socio-economic profiles at the district level. The analysis offered in this study also points to a decreased socially mixed society in 2011 when the deprived groups lived in districts with less presence of the advantaged population. 相似文献
964.
In current seismic design procedures, base shear is calculated by the elastic strength demand divided by the strength reduction factor. This factor is well known as the response modification factor, R, which accounts for ductility, overstrength, redundancy, and damping of a structural system. In this study, the R factor accounting for ductility is called the ‘ductility factor’, Rμ. The Rμ factor is defined as the ratio of elastic strength demand imposed on the SDOF system to inelastic strength demand for a given ductility ratio. The Rμ factor allows a system to behave inelastically within the target ductility ratio during the design level earthquake ground motion. The objective of this study is to determine the ductility factor considering different hysteretic models. It usually requires large computational efforts to determine the Rμ factor. In order to reduce the computational efforts, the Rμ factor is prepared as a functional form in this study. For this purpose, statistical studies are carried out using forty different earthquake ground motions recorded at a stiff soil site. The Rμ factor is assumed to be a function of the characteristic parameters of each hysteretic model, target ductility ratio and structural period. The effects of each hysteretic model to the Rμ factor are also discussed. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
965.
An instantaneous unit sediment graph (IUSG) model in conjunction with Kalman filter was investigated for prediction of sediment yield from an upland watershed in Northwestern Mississippi. The state vector of the watershed sediment yield system was constituted by the IUSG and then the sediment yield was estimated by the IUSG model using Kalman filter. The initial values of the state vector were assumed as the average of the IUSG values and the initial sediment yield estimated from the average IUSG. The IUSG model using Kalman filter with a recursive algorithm accurately predicted sediment yield from watershed W‐5, Mississippi. The filter allowed the IUSG to vary in time, increased the accuracy of the IUSG model, and reduced physical uncertainty of the sediment yield process in the watershed. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
966.
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. 相似文献
967.
3D joint inversion of magnetotelluric and airborne tipper data: a case study from the Morrison porphyry Cu–Au–Mo deposit,British Columbia,Canada 下载免费PDF全文
Benjamin M. Lee Martyn J. Unsworth Juliane Hübert Jeremy P. Richards Jean M. Legault 《Geophysical Prospecting》2018,66(2):397-421
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. 相似文献
968.
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. 相似文献
969.
Investigation of the dynamic behaviour of a storage tank with different foundation types focusing on the soil‐foundation‐structure interactions using centrifuge model tests 下载免费PDF全文
Heon‐Joon Park Jeong‐Gon Ha Sun‐Yong Kwon Moon‐Gyo Lee Dong‐Soo Kim 《地震工程与结构动力学》2017,46(14):2301-2316
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. 相似文献
970.
Concentrated, ‘pulsed’ axial glacier flow: structural glaciological evidence from Kvíárjökull in SE Iceland 下载免费PDF全文
Emrys Phillips Jez Everest David J.A. Evans Andrew Finlayson Marek Ewertowski Ailsa Guild Lee Jones 《地球表面变化过程与地形》2017,42(13):1901-1922
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. 相似文献