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   

Tempos of Elderly Age and Geographical Concentration*   总被引：1，自引：0，他引：1  

Andrei Rogers  Jennifer A. Woodward 《The Professional geographer》1992,44(1):72-83

This paper presents a method to measure two types of tempos: 1) the tempo of elderly age concentration, the rate of change in the elderly proportion in a region; and 2) the tempo of elderly geographical concentration, the rate of change in a region's share of the national elderly population. The two measurements are applied to historical data for the United States. The results reveal that both tempos vary spatially and temporally. Relative tempos are also introduced to compare the indices between different age groups and regions.  相似文献   

Behind the recent tragedy in Rwanda     

Jennifer M. Olson 《GeoJournal》1995,35(2):217-222

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The earth surface processes and landforms bibliography     

Janet Bailey 《地球表面变化过程与地形》1993,18(9):869-871

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Petrochemical variations among mildly peralkaline (comendite) obsidians from the oceans and continents     

D. K. Bailey  R. Macdonald 《Contributions to Mineralogy and Petrology》1970,28(4):340-351

Eleven new analyses and modes of comendite obsidians are presented, and compared with all available data on similar rocks. Most specimens are aphyric or contain only sparse phenocrysts, most commonly alkali feldspar. The oxides SiO₂, Al₂O₃, Na₂O and K₂O total over ninety percent by weight in all analyses. Iron, as FeO, is the only other constituent rising above one percent by weight. When the analyses are projected into the system Na₂O-K₂O-Al₂O₃-SiO₂, oceanic and continental samples group differently. Oceanic specimens have a compositional spread ranging from trachytic to the quartz-feldspar cotectic zone, consistent with derivation through a trachyte magma stem. Continental comendites show a strong correlation with the experimentally determined quartz-feldspar minima along a path of increasing peralkalinity. These differences presumably reflect the contrasting environments of magma generation, and suggest an origin by partial melting within the continental crust for the continental comendite obsidians.  相似文献   

Carbonatite in the tuffs of the West Eifel,Germany     

P. E. Lloyd  D. K. Bailey 《Contributions to Mineralogy and Petrology》1969,23(2):136-139

Newly-discovered carbonatitic fragments from the West Eifel are described in terms of their petrography and trace-element content.  相似文献   

Summary of recent volcanic activity     

Jennifer?FelaEmail author 《Bulletin of Volcanology》2003,65(8):622-623

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Preliminary evidence for human fecal contamination in corals of the Florida Keys,USA   总被引：6，自引：0，他引：6  

Lipp EK  Jarrell JL  Griffin DW  Lukasik J  Jacukiewicz J  Rose JB 《Marine pollution bulletin》2002,44(7):666-670

Corals and reef environments are under increased stress from anthropogenic activities, particularly those in the vicinity of heavily populated areas such as the Florida Keys. The potential adverse impacts of wastewater can affect both the environment and human health; however, because of the high decay rate of bacterial indicators in coral reef waters it has been difficult to document the presence of microbial contaminants and to assign risks in these environments. Here we show initial evidence that microorganisms associated with human feces are concentrated along the surface of coral heads relative to the overlying water column in the Florida Keys. Bacterial indicators (fecal coliform bacteria, enterococci or Clostridium perfringens) were detected in 66.7% of the coral surface microlayer (CSM) samples at levels between five and 1000 CFU/100 ml, but were found infrequently and at low numbers in the overlying water column ( < or = 2.5 CFU/100 ml). Similarly, enterovirus nucleic acid sequences, an indicator of human-specific waste, were detected in 93.3% of the CSM samples and only once in the water column by cell culture. Results show that coral mucus may accumulate enteric microorganisms in reef environments, and may indicate a risk to public and environmental health despite low indicator levels in the surrounding water.  相似文献   

Extensions to Spatial Factor Methods with an Illustration in Geochemistry     

T. C. Bailey  W. J. Krzanowski 《Mathematical Geology》2000,32(6):657-682

Many applications involving spatial data require several layers of information to be simultaneously analyzed in relation to underlying geography and topographic detail. This in turn generates a need for forms of multivariate analysis particularly oriented to spatial problems and designed to handle spatial structure and dependency both within and between spatially indexed multivariate responses. In this paper we focus on one group of such methods sometimes referred to as spatial factor analysis. Use of these techniques has so far been mostly restricted to applications in the geosciences and in some forms of image processing, but the methods have potential for wider use outside these fields. They are concerned with identifying components of a multivariate data set with a spatial covariance structure that predominantly acts over a particular spatial range or zone of influence. We review the various forms of spatial factor analysis that have been proposed and emphasize links between them and with the linear model of coregionalization employed in geostatistics. We then introduce extensions to such methods that may prove useful in exploratory spatial analysis, both generally and more specifically in the context of multivariate spatial prediction. Application of our proposed exploratory techniques is demonstrated on a small but illustrative geochemical data set involving multielement measurements from stream sediments.  相似文献   

Gullying and erosion control at archaeological sites in Grand Canyon,Arizona   总被引：1，自引：0，他引：1  

Joel L. Pederson  Paul A. Petersen  Jennifer L. Dierker 《地球表面变化过程与地形》2006,31(4):507-525

Gully erosion of cultural sites in Grand Canyon National Park is an urgent management problem that has intensified in recent decades, potentially related to the effects of Glen Canyon Dam. We studied 25 gullies at nine sites in Grand Canyon over the 2002 monsoon–erosion season to better understand the geomorphology of the gully erosion and the effectiveness of erosion‐control structures (ECS) installed by the park under the direction of the Zuni Conservation Program. Field results indicate that Hortonian overland flow leads to concentrated flow in gullies and erosion focused at knickpoints along channels as well as at gully heads. Though groundcover type, soil shear strength and permeability vary systemat‐ically across catchments, gradient and, to a lesser degree, contributing drainage area seem to be the first‐order controls on gully extent, location of new knickpoints, and ECS damage. The installed ECS do reduce erosion relative to reaches without them and initial data suggest woody checkdams are preferable to rock linings, but maintenance is essential because damaged structures can exacerbate erosion. Topographic data from intensive field surveys and detailed photogrammetry provide slope–contributing area data for gully heads that have a trend consistent with previous empirical and theoretical formulations from a variety of landscapes. The same scaling holds below gully heads for knickpoint and ECS topographic data, with threshold coefficients the lowest for gully heads, slightly higher for knickpoints, and notably higher for damaged ECS. These topographic thresholds were used with 10‐cm digital elevation models to create simple predictive models for gully extent and structure damage. The model predictions accounted for the observed gullies but there are also many false‐positives. Purely topographical models are probably inadequate at this scale and application, but models that also parameterize the variable soil properties across sites would be useful for predicting erosion problems and ECS failure. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献