P-wave velocity structure under the Changbaishan volcanic region, NE China, from wide-angle reflection and refraction data   总被引：3，自引：0，他引：3  

Jianli Song  Eric A. Hetland  Francis T. Wu  Xiankang Zhang  Guodong Liu  Zhuoxin Yang 《Tectonophysics》2007,433(1-4):127-139

We present velocity models determined by inverting refracted and reflected arrivals along two active source lines in the Changbaishan volcanic region, NE China. We resolve a prominent low-velocity zone (LVZ) in the crust, with velocities as low as 5.4 km/s. Away from the LVZ, the velocity gradients in the crust are relatively smooth, with average P-wave velocities of about 6.0–6.5 km/s. The Moho is at about 35 km depth, thickening to about 40 km under the Tianchi volcano, and thinning to about 30 km under the LVZ. The LVZ is located about 30–60 km to the north of the summit of the Tianchi volcano (the most recently active volcano in the region), is about 30–75 km in north–south extent, is at most 35 km in east–west extent, and is in the depth range of about 10–25 km below the surface. We use these results to constrain receiver function inversions, and show that the receiver functions in the region are compatible with our findings. With these data alone, the significance of the LVZ in non-unique, although we do not see any evidence to support the presence of partial melt in the crust, and favor the interpretation that the LVZ indicates a residual crustal magma chamber.  相似文献   

The Spatial Structure of Land Use from 1970–2000 in the Phoenix,Arizona, Metropolitan Area     

Eric Keys  Elizabeth A. Wentz  Charles L. Redman 《The Professional geographer》2007,59(1):131-147

This article explores the dimensions of rapid urbanization in the Phoenix Standard Metropolitan Statistical Area (SMSA) over the past thirty years with respect to land use change. We devote primary attention to developing an understanding of what land transformations took place, the extent to which they occurred, and where they occurred. Our findings indicate that 32 percent of the Phoenix SMSA changed between 1970 and 2000. More than half of the overall change was from agriculture to some form of urban land use, and although a large percentage of the region remains open desert the parcels of desert are increasingly fragmented. This has significant implications for urban ecology and biodiversity. The growth indicates that rather than a pattern that reflects the agglomeration effects of a polycentric metropolis, the central business district of the City of Phoenix dominates the region. This has implications with respect to employment patterns, traffic congestion, and urban air quality and climate.  相似文献   

Latin America: Regions and People by Robert B. Kent     

Eric D. Carter 《The Professional geographer》2007,59(1):151-153

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Prograde and retrograde history of the Junction School eclogite,California, and an evaluation of garnet–phengite–clinopyroxene thermobarometry     

F. Zeb Page  Lora S. Armstrong  Eric J. Essene  Samuel B. Mukasa 《Contributions to Mineralogy and Petrology》2007,153(5):533-555

Quantitative thermobarometry of inclusions in zoned garnet from a Franciscan eclogite block record a counter-clockwise P–T path from blueschist to eclogite and back. Garnet retains prograde zoning from inclusion-rich Alm₅₂Grs₃₀Pyp₆Sps₁₂ cores to inclusion-poor Alm₆₂Grs₂₅Pyp₁₂Sps₁ mantles, with overgrowths of highly variable composition. Barometry using the Waters–Martin version of the garnet–phengite–omphacite thermobarometer yields conditions of 7–15 kbar, 400–500°C (garnet cores), 18–22 kbar, ∼550°C (mantles), and 10–14 kbar, 350–450°C (overgrowths), in agreement with clinozoisite–sphene–rutile–garnet–quartz barometry. These pressures are ∼10–15 kbar less than those obtained using more recent, fully thermodynamic calibrations of the phengite–omphacite–garnet thermobarometer. Low early temperatures suggest that the block was subducted in a thermally mature subduction zone and not at the inception of subduction when prograde temperature is expected to be higher. Franciscan high-grade blocks likely represent crust subducted throughout the history of this convergent margin, rather than only at the inception of the subduction zone.  相似文献   

High-order <Emphasis Type="Italic">h</Emphasis>-adaptive discontinuous Galerkin methods for ocean modelling     

Paul-Emile Bernard  Nicolas Chevaugeon  Vincent Legat  Eric Deleersnijder  Jean-François Remacle 《Ocean Dynamics》2007,57(6):579-580

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Influence of the turbulence closure scheme on the finite-element simulation of the upwelling in the wake of a shallow-water island     

Sébastien Blaise  Eric Deleersnijder  Laurent White  Jean-François Remacle 《Continental Shelf Research》2007

A three-dimensional finite-element model is used to investigate the tidal flow around Rattray Island, Great Barrier Reef, Australia. Field measurements and visual observations show both stable eddies developing at rising and falling tide in the wake of the island. The water turbidity suggests intense upwelling able to carry bed sediments upwards. Based on previous numerical studies, it remains unclear at this point whether the most intense upwelling occurs near the centre of the eddies or off the island's tips, closer to the island. All these studies resorted to a very simple turbulence closure, with a zero-equation model whereby the coefficient of vertical viscosity is computed via an algebraic expression. In this work, we aim at studying the influence of the turbulence closure on model results, with emphasis on the prediction of vertical motions. The Mellor and Yamada level 2.5 closure scheme is used and an increase in the intensity of vertical transport is observed. This increase is partly explained by the fact that the Mellor and Yamada model takes into account the hysteresis effect in the time variation of turbulence variables. The influence of the advection of turbulence variables is estimated to be negligible. By a better representation of transient coastal phenomena, the Mellor and Yamada level 2.5 turbulence closure improves the model to a significant degree.  相似文献   

Scaling characteristics of spatial patterns of soil moisture from distributed modelling   总被引：1，自引：0，他引：1  

Salvatore Manfreda  Matthew F. McCabe  Mauro Fiorentino  Ignacio Rodríguez-Iturbe  Eric F. Wood 《Advances in water resources》2007

Characterizing the spatial dynamics of soil moisture fields is a key issue in hydrology, offering an avenue to improve our understanding of complex land surface–atmosphere interactions. In this paper, the statistical structure of soil moisture patterns is examined using modelled soil moisture obtained from the North American Land Data Assimilation System (NLDAS) at 0.125° resolution. The study focuses on the vertically averaged soil moisture in the top 10 cm and 100 cm layers. The two variables display a weak dependence for lower values of surface soil moisture, with the strength of the relationship increasing with the water content of the top layer. In both cases, the variance of the soil moisture follows a power law decay as a function of the averaging area. The superficial layer shows a lower degree of spatial organization and higher temporal variability, which is reflected in rapid changes in time of the slope of the scaling functions of the soil moisture variance. Conversely, the soil moisture in the top 100 cm has lower variability in time and larger spatial correlation. The scaling of these patterns was found to be controlled by the changes in the soil water content. Results have implications for the downscaling of soil moisture to prevent model bias.  相似文献   

Receiver function analysis for seismic structure of the crust and uppermost mantle in the Liupanshan area, China     

TONG WeiWei  WANG LiangShu  MI Ning  XU MingJie  LI Hua  YU DaYong  LI Cheng  LIU ShaoWen  LIU Mian  Eric SanDvol 《中国科学D辑(英文版)》2007,50(Z2):227-233

A portable broadband seismic array was deployed from the northeast Tibetan Plateau to the southwest Ordos block, China. The seismic structure of the crust and uppermost mantle of the Liupanshan area is obtained using receiver function analysis of teleseismic body waves. The crustal thickness and Poisson's ratios are estimated by stacking the weighted amplitudes of receiver functions. Our results reveal complex seismic phases in the Liupanshan area, implying intense deformation at the boundary between the Tibetan Plateau and the Ordos block. The average crustal thickness is 51.5 km in the northeast Tibetan Plateau, 53.5 km in the Liupan Mountain and 50 km in the southwest Ordos block, resulting in a concave Moho beneath the Liupan Mountain. The Poisson's ratio of the Liupanshan area varies between 0.27-0.29, higher than the value of 0.25-0.26 to the east and west of the Liupan Mountain, suggesting partial melting in the lower crust. The variance in Poisson's ratio across the Liupan Mountain indicates notable changes in the crustal composition and mechanical properties, which may be formed by the northeastward flow of the Tibetan lower crust during the India-Eurasia collision.  相似文献   

A correction to McAllister's 1960 atlas of the solar spectrum     

Eric G. Chipman 《Solar physics》1974,36(1):45-48

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Modelling the effects of cross-sectoral water allocation schemes in Europe     

Florian Wimmer  Eric Audsley  Marcus Malsy  Cristina Savin  Robert Dunford  Paula A. Harrison  Rüdiger Schaldach  Martina Flörke 《Climatic change》2015,128(3-4):229-244

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