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排序方式: 共有173条查询结果,搜索用时 15 毫秒
141.
This study analyzes data recorded at the dense array in the Parkway Valley, Wainuiomata, New Zealand, a small alluvial valley surrounded by graywacke outcrops. The array consisted of stations on both the sediment basin and the surrounding soft rock, with station separation distances pertinent for earthquake engineering applications. The array's configuration renders itself uniquely for the study of the spatial variation of seismic ground motions at sites with irregular topography for bridge response evaluations: the locations of the soft-rock stations surrounding the valley may be viewed as the locations of the bridge's abutments, and the locations of the stations in the basin as those of the bridge's intermediate piers. A further-away station, north-east of the valley, provided information on firm-rock data. 相似文献
142.
Randell A. Stephenson Ryszard Dadlez Marek Narkiewicz 《Studia Geophysica et Geodaetica》1995,39(3):289-297
Summary Tectonic subsidence analysis of the preserved and reconstructed stratigraphy of the Polish Basin indicates an initial Late Permian-Early Triassic (255-241 Ma) syn-rift phase of development with a subsequent extensional rejuvenation during the Late Jurassic (ca. 157-152 Ma). Forward modelling of the subsidence data, in view of existing geophysical interpretations which show the presence of a deep Moho and a very high seismic velocity lower crustal layer beneath the Mid-Polish Trough (MPT), suggest that Permo-Mesozoic basin development may be related at least in part to the intrusion of mantle material into and densification of the lower crust rather than exclusively to crustal extension and thinning. 相似文献
143.
The natural (electrical) potential (NP) method – also known as self-potential, spontaneous potential and streaming potential
(SP) – has been used to locate areas of groundwater flow in karst terrane. NP is the naturally occurring voltage at the ground
surface resulting from ambient electrical currents within the earth. The measurement of NP can be used to characterize groundwater
flow in karst terrane because electrical potential gradients are generated by the horizontal flow of water along fractures
or conduits and the vertical infiltration of water into fractures or shafts. NP data from a site on the Mitchell Plain of
southern Indiana, USA, revealed that NP data can be decomposed into three components: topographic effect, residual NP and
noise. At this site, NP was inversely proportional to elevation, but the correlation varied with time. The topographic correction
factor varied from –2.5 to –1.2 mV/m (NP change per unit elevation increase), with an average linear correlation coefficient
(R) of 0.95. Because the site slopes toward an adjacent creek that is the local groundwater discharge zone, one possible explanation
for this effect is a streaming-potential mechanism generated by groundwater movement toward the creek. The residual NP data
revealed three negative anomalies at the survey area. Two of them coincide with sinkholes. A part of the third anomaly is
coincident with a small valley, and concentrated infiltration does occur at this elevation in other valleys at the site, as
evidenced by the existence of sinkholes. However, the dispersed, low-magnitude nature of the third anomaly does not prove
the existence of concentrated groundwater recharge activity.
Received: 18 March 1998 · Accepted: 27 April 1998 相似文献
144.
Hunter James A. Crow Heather L. Stephenson William J. Pugin André J.-M. Williams Robert A. Harris James B. Odum Jack K. Woolery Edward W. 《Journal of Seismology》2022,26(4):631-652
Journal of Seismology - Reflection and critically refracted seismic methods use traveltime measurements of body waves propagating between a source and a series of receivers on the ground surface to... 相似文献
145.
146.
Runjie Yuan David M. Kennedy Wayne J. Stephenson Lluís Gómez-Pujol 《地球表面变化过程与地形》2019,44(7):1377-1389
In this study laboratory experiments were used to explore the role of biofilms, formed by lithobiontic microorganism communities, in causing hourly surface changes of supratidal sandstone and the potential linkage to long-term rock decay. To isolate the influence of individual environmental factors (temperature and humidity) on rock surface changes (expansion and contraction), a colonized (biofilm-covered) and a non-colonized sandstone block (biofilm-free) underwent the same univariate microclimatic simulations closely controlled by an environmental chamber. Simulations were run under three different light conditions, with a natural light lamp on, on and off at 20-min intervals and off, to investigate the impact of light on rock surface dynamics. Measured with a traversing micro-erosion meter (TMEM), two-hourly microtopographic fluctuations of these two sandstone blocks were compared in the same environment. Induced by microclimatic variations, surface movements of significantly higher magnitude (12–120% under varying tempeature and 121–154% under varying humidity) and different change patterns were observed on the colonized block, indicating the primary role of biofilm in driving microtopographic fluctuations of supratidal sandstone. However, thermally driven changes of similar magnitude and pattern were observed on both surfaces, suggesting other mechanisms also operating on the non-colonized rock surface in this process. Due to the sensitivity of biofilm microorganism communities to light, the magnitude and pattern of surface changes was impacted by light condition. Because biofilms increased the magnitude and number of cycles of expansion and contraction of the experimental rock surface, we propose that lithobiontic biofilms facilitate the detachment of grains and granular disintegration on the rock surface, consequently contributing to rock decay and accelerating the rate of breakdown of supratidal rock. This short-term episode therefore needs to be superimposed on longer term studies to fully understand the role of biofilms in rock surface change. © 2019 John Wiley & Sons, Ltd. 相似文献
147.
This paper presents measured rates of erosion on shore platforms at Kaikoura Peninsula, South Island, New Zealand. Surface lowering rates were measured with a micro-erosion meter and traversing micro-erosion meter. The mean lowering rate for all shore platforms was 1·130 mm a−1. Differences in lowering rates were found between different platform types and lithologies. The rate of surface lowering on Type A (sloping) mudstone platforms was 1·983 mm a−1, and 0·733 mm a−1 on Type B mudstone platforms (subhorizontal). On limestone platforms the lowering rate was 0·875 mm a−1. A previously reported cross-shore pattern of surface lowering rates from Kaikoura was not found. Rates were generally higher on the landward margins and decreased in a seaward direction. Season is shown statistically to influence erosion rates, with higher rates during summer than winter. The interpretation given to this is that the erosive process is subaerial weathering in the form of wetting and drying and salt weathering. This is contrary to views of shore platform development that have favoured marine processes over subaerial weathering. Copyright © 1998 John Wiley & Sons, Ltd. 相似文献
148.
149.
Hayakawa Hisashi Sôma Mitsuru Tanikawa Kiyotaka Willis David M. Wild Matthew N. Macdonald Lee T. Imada Shinsuke Hattori Kentaro Richard Stephenson F. 《Solar physics》2019,294(9):1-13
Solar Physics - Large sunspots can be observed with the unaided eye under suitable atmospheric seeing conditions. Such observations are of particular value because the frequency of their appearance... 相似文献
150.
Claudia Baldwin Graham Marshall Helen Ross Jim Cavaye Janet Stephenson Lyn Carter 《社会与自然资源》2019,32(5):566-587
Neoliberalism is frequently blamed for challenges in achieving sustainable development; consequently some also question if sustainability is still a useful concept. Neoliberal influence on natural resource management has evolved over the last 30?years to a hybrid form that seeks to compensate for its negative social and environmental externalities. Through review of literature and critical analysis of three case studies of resource development in Australia and New Zealand, we argue that, in spite of modifications under hybrid approaches, neoliberalism still tests achievement of sustainability goals, due to privileging industry and shifting risk and costs to future generations, through inadequate regulation, neglect of public consultation, lack of transparency, and weak impact assessment. We suggest that while neoliberal approaches bring both benefits and disadvantages, sustainability principles must continue to be kept at the forefront of legislation, regulation and management. 相似文献