Spatial variability of liquefaction potential in regional mapping using CPT and SPT data   总被引：5，自引：0，他引：5  

Jennifer A. Lenz  Laurie G. Baise   《Soil Dynamics and Earthquake Engineering》2007,27(7):690-702

Cone penetration test (CPT) and standard penetration test (SPT) are widely used for the site specific evaluation of liquefaction potential and are getting increased use in the regional mapping of liquefaction hazard. This paper compares CPT and SPT-based liquefaction potential characterizations of regional geologic units using the liquefaction potential index (LPI) across the East Bay of the San Francisco Bay, California, USA and examines the statistical and spatial variability of LPI across and within geologic units. Overall, CPT-based LPI characterizations result in higher hazard than those derived from the SPT. This bias may result from either mis-classifications of soil type in the CPT or a bias in the CPT simplified procedure for liquefaction potential. Regional mapping based on cumulative distribution of LPI values show different results depending on which dataset is used. For both SPT and CPT-based characterizations, the geologic units in the area have broad LPI distributions that overlap between units and are not distinct from the population as a whole. Regional liquefaction classifications should therefore give a distribution, rather than a single hazard rating that does not provide for variability within the area. The CPT-based LPI values have a higher degree of spatial correlation and a lower variance over a greater distance than those estimated from SPTs. As a result, geostatistical interpolation can provide a detailed map of LPI when densely sampled CPT data are available. The statistical distribution of LPI within specific geologic units and interpolated maps of LPI can be used to understand the spatial variability of liquefaction potential.  相似文献   

Large-Eddy Simulation Of Neutral Turbulent Flow Over Rough Sinusoidal Ridges     

A. R. Brown  J. M. Hobson  N. Wood 《Boundary-Layer Meteorology》2001,98(3):411-441

The requirements for a credible large-eddy simulation of neutral, turbulent flow over hills with an aerodynamically rough surface are discussed, in order to select a suitable case for simulation. As well as providing adequate resolution within the dynamically important inner region, obtaining a realistic upstream or undisturbed mean velocity profile is also of critical importance. A distributed drag canopy formulation has been introduced to the model to allow it to obtain such a profile while resolving very close to the rough surface. Simulations have then been performed of flow over ridges of varying heights. The results from the steepest case, which is just on the verge of separation, are compared with wind-tunnel observations. It is shown that the large-eddy simulation results are in much better agreement with the experimental data than are the results from a simple first-order mixing-length closure model. An encouraging lack of sensitivity of the simulation results to numerical resolution is also demonstrated.  相似文献   

Direct measurements of volume transports through Fram Strait   总被引：9，自引：1，他引：9  

Eberhard Fahrbach  Jens Meincke  Svein Østerhus  Gerd Rohardt  Ursula Schauer  Vigdis Tverberg  Jennifer Verduin 《Polar research》2001,20(2):217-224

Heat and freshwater transports through Fram Strait are understood to have a significant influence on the hydrographic conditions in the Arctic Ocean and on water mass modifications in the Nordic seas. To determine these transports and their variability reliable estimates of the volume transport through the strait are required. Current meter moorings were deployed in Fram Strait from September 1997 to September 1999 in the framework of the EU MAST III Variability of Exchanges in the Northern Seas programme. The monthly mean velocity fields reveal marked velocity variations over seasonal and annual time scales, and the spatial structure of the northward flowing West Spitsbergen Current and the southward East Greenland Current with a maximum in spring and a minimum in summer. The volume transport obtained by averaging the monthly means over two years amounts to 9.5 ± 1.4 Sv to the north and 11.1 ± 1.7 Sv to the south (1 Sv = 10⁶ m³s⁻¹). The West Spitsbergen Current has a strong barotropic and a weaker baroclinic component; in the East Greenland Current barotropic and baroclinic components are of similar magnitude. The net transport through the strait is 4.2 ± 2.3 Sv to the south. The obtained northward and southward transports are significantly larger than earlier estimates in the literature; however, within its range of uncertainty the balance obtained from a two year average is consistent with earlier estimates.  相似文献   

Impact of prescribed burning on Acacia nilotica seed banks and seedlings in the Astrebla grasslands of northern Australia     

Ian J. Radford  D. Michael Nicholas  Joel R. Brown 《Journal of Arid Environments》2001,49(4):795

Acacia nilotica is a tree of international significance both as a beneficial plant and as a species prone to thicket formation and negative impacts on savannas throughout much of its range. While fire has been identified as a useful tool for controlling negative impacts of some Acacia species in Africa, A. nilotica adult trees are apparently fire tolerant. The effects of fire on seed bank mortality, viability and germination, and on juvenile plants of this species are unknown. We undertook a study to investigate the impacts of fire on seeds and first and second year seedlings in Australian Astrebla savannas. The primary objective was to determine the effects of control burns applied during the early stages of invasion and thicket formation. Because of high rates of seedling dessication post fire in 1997, supplementary watering was undertaken until fire mortality could be measured the following year. High seed mortality occurred for seeds located either in cattle dung (100%) or on the soil surface (c. 80%). Germination of those seeds that survived was enhanced following exposure to fire. Very high fire mortality (99%) was observed among first year seedlings and moderate mortality (60%) for second year seedlings even after a low intensity burn. Negative impacts on major pasture species were minimal. The implications of these findings are discussed in relation to A. nilotica fire ecology and to the efficacy of fire as a tool for managing this species.  相似文献   

DNAPL Removal from a Heterogeneous Alluvial Aquifer by Surfactant- Enhanced Aquifer Remediation     

John T. Londergan  Hans W. Meinardus  Paul E. Manner  Richard E. Jackson  Chris L. Brown  Varadarajan Dwarakanath  Gary A. Pope  Jon S. Ginn  Sam Taffinder 《Ground Water Monitoring & Remediation》2001,21(3):71-81

  相似文献   

Calibrate yourself to your data! A vital first step in seismic interpretation     

Alistair R. Brown 《Geophysical Prospecting》2001,49(6):729-733

Stratigraphic, reservoir and fluid interpretation demands a thorough understanding of the seismic-to-well tie. Data phase, polarity and tuning effects significantly influence this tie and are often poorly understood. By relating seismic character to known subsurface geology, the interpreter should gain better understanding and be able to calibrate himself to his data. This is an important preliminary stage in any seismic interpretation beyond structure.  相似文献   

Rheology and geodynamic modelling: the next step forward     

M. Handy  J. Braun  M. Brown  N. Kukowski  M. Paterson  S. Schmid  B. Stöckhert  K. Stüwe  A. Thompson  E. Wosnitza 《International Journal of Earth Sciences》2001,90(1):149-156

The application of continuum mechanics and microstructural analysis to geological studies over the past 30 years has spurred earth scientists to reassess fundamental tectonic processes such as subduction, collision and rifting in terms of dynamics. Armed with new analytical methods, geologists have returned to the field to look at rock structures with more mechanistic eyes. The advent of sophisticated computers, programs, and laboratory deformation equipment has facilitated the simulation of geodynamic processes that range in scale from the grain to the lithosphere. The result has been specialization, with the concomitant opening of communication gaps between geodynamicists, field geologists and rock mechanicists. Partly, these gaps reflect differences of perception and approach. In order to bridge these gaps, a workshop was organized after the DRM conference to debate how field and laboratory studies of deformed rocks can improve our understanding of lithospheric rheology, and in turn, how this understanding can be used to refine dynamic models of orogenesis. The workshop hosted participants with backgrounds in structural geology, experimental rock mechanics, metamorphic petrology and both numerical and analogue modelling. This paper summarizes the main controversies and conclusions reached during the workshop. For the sake of brevity, referencing in this summary is restricted to literature referred to during the oral presentations and to comments made by speakers themselves (names italicized).  相似文献   

The Holocene paleohydrology and climatic history of the northern great sandy desert - fitzroy trough: With special reference to the history of the northwest Australian monsoon     

Karl-Heinz Wyrwoll  Jennifer Hopwood  N. L. McKenzie 《Climatic change》1992,22(1):47-65

The Holocene history of the northwest Australian monsoon is considered in the light of new stratigraphic findings from the southern margin of the monsoon regime. A discussion of the present-day climatology of northwestern Australia and synoptic controls on precipitation in the areas at the southern margin of the monsoon regime is given as background information for the interpretation of stratigraphic findings from swamp and alluvial sequences. The stratigraphic findings point to little change in the intensity of the northwest Australian monsoon since ca. 6.5 ka. A more tentative inference drawn from the field evidence is that the monsoon activity may well have been reduced in this region during the Early Holocene; during this time insolation levels were also reduced. The possible relationship of the northwest Australian monsoon to insolation levels is explored. It is clear that monsoon behavior cannot be accounted for as a simple linear response of monsoon intensity to variations in insolation. Possible controls are discussed with particular emphasis on the plausibility of changes in the damping of convective motions providing the mechanism. Gill's model of heat-induced circulation is used to provide some evidence in favour of this conjecture.  相似文献   

Use of a reservoir water quality model to simulate global climate change effects on fish habitat     

Lisa H. Chang  Steven F. Railsback  Russell T. Brown 《Climatic change》1992,20(4):277-296

A case study was conducted on the potential impacts of climate change on fish habitat in a southeastern reservoir. A reservoir water quality model and one year of baseline meteorologic, hydrologic, and inflow water quality input were used to simulate current reservoir water quality. Total adult striped bass habitat, defined by specific quantitative temperature and dissolved oxygen criteria, was simulated. Daily reservoir volumes with optimal, suboptimal, and unsuitable temperature and DO were predicted for the year. Output from recent runs of atmospheric general circulation models (GCMs), in which atmospheric carbon dioxide concentrations have been doubled, was then used to adjust the baseline inputs to the water quality model. New sets of input data were created for two grid cells for each of three GCMs. All six climate scenarios are predicted to cause overall declines in the available summer striped bass habitat, mostly due to lake water temperatures exceeding striped bass tolerance levels. These predictions are believed to result from the consensus among GCM scenarios that air temperatures and humidity will rise, and the sensitivity of the reservoir model to these parameters. The reservoir model was found to be a promising tool for examining potential climate-change impacts. Some of the assumptions required to apply GCM output to the reservoir model, however, illustrate the problems in using large-scale gridcell output to assess small-scale impacts.  相似文献   

Site-dependent models of earthquake ground motion     

Jennifer M. O'connor  Bruce R. Ellingwood 《地震工程与结构动力学》1992,21(7):573-589

Random vibration analyses of structural systems subjected to seismic loading are dependent upon the characterization of earthquake ground motion as a stochastic process. The response of structural systems to earthquakes is dependent strongly on the local geological conditions, which should be incorporated into seismological models of ground motion. In the study presented herein, three previously developed ground-motion models are adapted to incorporate site-dependent characteristics. Records obtained from two recording stations in California are used as a basis for the ground-motion models. Single-degree-of-freedom (SDOF) oscillators are subjected to ensembles of accelerograms generated from these models, and both elastic and inelastic response are considered. Response statistics are compared to those generated by the analysis of structural response to ensembles of recorded motion from the two sites. The important features of the ground motion for effective reproduction of response statistics are identified, and observations are made on the sensitivity of specific response parameters to site-dependent characteristics of the ground motion.  相似文献