Dissolved and particulate organic carbon in the North Inlet estuary,South Carolina: What controls their concentrations?     

Thomas G. Wolaver  Steve Hutchinson  Marvin Marozas 《Estuaries and Coasts》1986,9(1):31-38

Water samples have been taken daily at 1030 EST from three locations within North Inlet (South Carolina) since June of 1980 in order to evaluate the tidal, seasonal, and eventually annual variability in carbon concentrations within this system and generate hypotheses explaining the observed trends. Dissolved organic carbon (DOC) concentrations within North Inlet (South Carolina) vary inversely with salinity (r²=0.65), suggesting the main source of DOC in North Inlet is freshwater entering from the adjacent forested watershed. This assertion is supported by an observed decrease of tidal water salinity with the onset of streamflow. DOC variability is also associated with (1) groundwater advection and/or runoff and seepage from the marsh surface; (2) removal from tidal water via either physical sorption or biological uptake; (3) sampling location; and (4) origin of water mass. Particulate organic carbon (POC) concentrations vary seasonally, higher values found during the summer. POC variability is controlled by a series of physical and biological factors. Evidence suggests that in the smaller tidal creeks, POC concentrations are associated with (1) rain events scouring the marsh surface, (2) phytoplankton concentrations varying as a function of tidal stage, and (3) removal of particulate material from the marsh surface on the ebb tide. In the larger tidal creeks tidal water velocity appears to be the main factor influencing POC values.  相似文献   

Evaluation of code torsional provisions by a time history approach     

A. M. Chandler  G. L. Hutchinson 《地震工程与结构动力学》1987,15(4):491-516

Presented in this paper is a detailed parametric study of the coupled lateral and torsional response of single-storey building models subjected to earthquake base loadings. The aim is to assess the influence of torsional coupling on the elastic responses of buildings subjected to transient ground motion records, and to make comparisons with current code provisions which make allowance for coupling effects by means of empirical design procedures. The study of building responses to selected earthquake excitations shows that the qualitative effects of the controlling parameters on the maximum translational and torsional responses of the coupled system are similar to those observed in analyses using idealized response spectra to represent the input ground motion. It is also demonstrated that for particular ranges of the key parameters defining the structural system, typical of the properties of many actual buildings, torsional coupling induces significant amplification of earthquake forces. This amplification is shown to be inadequately accounted for in the current design provisions of major building codes. Recommendations for improving existing design practice for asymmetric structures are outlined.  相似文献   

Evolution of the modern Nile delta promontories: development of accretional features during shoreline retreat   总被引：1，自引：0，他引：1  

Omran Frihy  Deborah Lawrence 《Environmental Geology》2004,46(6-7):914-931

The active accretional features that have developed along the modern Nile Delta promontories during shoreline retreat are analysed using topographic maps, remote imagery, ground and hydrographic surveys, together providing 15 time-slice maps (1922–2000) at Rosetta and 14 time-slice maps (1909–2000) at Damietta. Small double sandy spits developed and persisted at Rosetta between 1986 and 1991. At Damietta, a much larger single spit, 9 km long, formed approximately east of the mouth of the Damietta Nile branch between 1955 and 1972, although its source has now been depleted. Both the Rosetta and Damietta inlets are associated with submerged mouth bars that accumulated prior to the damming of the Nile, but that continue to contribute to local sedimentation problems, particularly at Rosetta. The development of the active accretional features along the Nile promontories reflects a combination of factors including sediment availability, transport pathways from source areas, a decrease in the magnitude of Nile flood discharges, as well as the impact of protective structures at the river mouths.  相似文献   

Response spectrum predictions for potential near-field and far-field earthquakes affecting Hong Kong: rock sites   总被引：1，自引：0，他引：1  

N. T. K. Lam  A. M. Chandler  J. L. Wilson  G. L. Hutchinson 《Soil Dynamics and Earthquake Engineering》2002,22(1)

To realistically assess the seismic risk relating to built infrastructures in Hong Kong and in the neighbouring coastal cities of southern Guangdong province, it is necessary to predict ground shaking induced by different earthquake scenarios with good accuracy. A companion paper has described the modelling of the spatial and temporal distribution of the diffused seismic activities in the region, based on the newly-developed ‘Expanding Circular Disc’ (ECD) method. Representative Magnitude–Distance (M–R) combinations for both near-field and far-field earthquakes (in relation to Hong Kong) have been derived using the ECD method. The present paper describes the modelling of the response spectrum on rock sites associated with the predicted M–R combinations, using the Component Attenuation Model (CAM) that was also developed recently by the authors, based on stochastic simulations of the seismological model. The significant effects of soil resonance on the response spectrum are described in a separate publication.The accuracy of CAM in modelling ground motion properties on rock sites has been tested here by comparisons with (i) strong motions recorded in Taiwan and South China from the 1999 ‘Chi-Chi’ earthquake in Taiwan (M=7.6), (ii) motions recorded in South China from another earthquake occurring in the southern Taiwan Strait in the same year (M=5.1), and (iii) historical seismic intensity data obtained within South China. The overall capability of CAM in modelling both near-field and far-field attenuation has been shown to be unmatched by existing empirical models. Results of the comparison studies confirm the accuracy of CAM, particularly within an epicentral distance of 300–400 km.This study shows that the developed serviceability response spectra (i.e. at short return periods) are controlled mainly by the earthquake recurrence behaviour of major distant seismic sources. In contrast, the ultimate response spectra (i.e. at long return periods) relate to events with magnitudes close to the maximum credible earthquake (MCE) limit, the effect of which may also be represented by the Characteristic Response Spectrum (CRS). Both types of earthquake scenario can be significantly affected by the regional crustal properties. The proposed response spectrum envelopes have been compared with previously developed recommendations, and a critical review has been conducted. The intrinsic advantages of the ECD–CAM modelling approach have been highlighted, emphasising its directness and transparency when compared with the more complex process required to implement traditional Probabilistic Seismic Hazard Assessment (PSHA).  相似文献   

A comparison between subaerial and submarine eruptions at Kilauea Volcano, Hawaii: implications for the thermal viability of lateral feeder dikes     

Elisabeth A. Parfitt  Tracy K. P. Gregg  Deborah K. Smith 《Journal of Volcanology and Geothermal Research》2002,113(1-2)

Eruption styles on the subaerial East Rift Zone (ERZ) of Kilauea volcano are reviewed and a classification scheme for the different types of eruption is proposed. The various eruption types are produced by differing thermal and driving pressure behaviour in the feeder dikes. Existing evidence is reviewed and new evidence presented of the types and volumes of eruptions on the Puna Ridge, which is the submarine extension of the ERZ. Eruptions on the Puna Ridge fall into the same five classes as, and are of comparable volume to, those on the subaerial ERZ. Evidence is presented which suggests that feeder dikes for Puna Ridge eruptions are more thermally viable than those feeding subaerial eruptions, and this difference causes long-lived, large-volume eruptions to be more common on the Puna Ridge than on the subaerial ERZ. This systematic variation in thermal viability may be due to increased dike width for Puna Ridge dikes or increased pressure gradients driving magma flow. Lateral dike emplacement is common to many basaltic systems including on other Hawaiian volcanoes, in Iceland and at mid-ocean ridges. The systematic trend inferred for the ERZ of Kilauea implies that in the other systems large-volume eruptions may also be more common at great distances than they are close to the magma centre.  相似文献   

Guidelines for the good practice of surface wave analysis: a product of the InterPACIFIC project     

Sebastiano Foti  Fabrice Hollender  Flora Garofalo  Dario Albarello  Michael Asten  Pierre-Yves Bard  Cesare Comina  Cécile Cornou  Brady Cox  Giuseppe Di Giulio  Thomas Forbriger  Koichi Hayashi  Enrico Lunedei  Antony Martin  Diego Mercerat  Matthias Ohrnberger  Valerio Poggi  Florence Renalier  Deborah Sicilia  Valentina Socco 《Bulletin of Earthquake Engineering》2018,16(6):2367-2420

Surface wave methods gained in the past decades a primary role in many seismic projects. Specifically, they are often used to retrieve a 1D shear wave velocity model or to estimate the V_S,30 at a site. The complexity of the interpretation process and the variety of possible approaches to surface wave analysis make it very hard to set a fixed standard to assure quality and reliability of the results. The present guidelines provide practical information on the acquisition and analysis of surface wave data by giving some basic principles and specific suggestions related to the most common situations. They are primarily targeted to non-expert users approaching surface wave testing, but can be useful to specialists in the field as a general reference. The guidelines are based on the experience gained within the InterPACIFIC project and on the expertise of the participants in acquisition and analysis of surface wave data.  相似文献   

Hydrological model parameter (in)stability – “crash testing” the HBV model under contrasting flood seasonality conditions     

Klaus Vormoor  Maik Heistermann  Axel Bronstert  Deborah Lawrence 《水文科学杂志》2018,63(7):991-1007

This paper investigates the transferability of calibrated HBV model parameters under stable and contrasting conditions in terms of flood seasonality and flood generating processes (FGP) in five Norwegian catchments with mixed snowmelt/rainfall regimes. We apply a series of generalized (differential) split-sample tests using a 6-year moving window over (i) the entire runoff observation periods, and (ii) two subsets of runoff observations distinguished by the seasonal occurrence of annual maximum floods during either spring or autumn. The results indicate a general model performance loss due to the transfer of calibrated parameters to independent validation periods of ?5 to ?17%, on average. However, there is no indication that contrasting flood seasonality exacerbates performance losses, which contradicts the assumption that optimized parameter sets for snowmelt-dominated floods (during spring) perform particularly poorly on validation periods with rainfall-dominated floods (during autumn) and vice versa.  相似文献   

Analysis of nonlinear associations between prenatal methylmercury exposure from fish consumption and neurodevelopmental outcomes in the Seychelles Main Cohort at 17 years     

Li-Shan?HuangEmail authorView author&#;s OrcID profile  Deborah?A.?Cory-Slechta  Christopher?Cox  Sally?W.?Thurston  Conrad?F.?Shamlaye  Gene?E.?Watson  Edwin?van Wijngaarden  Grazyna?Zareba  J.?J.?Strain  Gary?J.?Myers  Philip?W.?Davidson 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(4):893-904

The Seychelles Child Development Study has been examining the relationship between prenatal methylmercury (MeHg) exposure from consuming fish during pregnancy and child development. This study re-analyzes seven outcomes in the 17 year Main Cohort data to determine if there are nonlinear or non-homogeneous (subgroup) associations that were not identified in the linear analysis. We adopted two statistical approaches. First, we carried out an additive nonlinear analysis assuming homogeneous prenatal MeHg-outcome relationships to explore overall associations. Second, we applied the regression tree to the Woodcock–Johnson Calculation subtest (it was significantly associated in earlier analyses) and identified 4 clusters based on covariates. Then we used additive models to assess the prenatal MeHg association in each of the four clusters for all seven outcomes. This approach assumes nonlinear associations in each cluster and non-homogeneous associations between clusters. The additive nonlinear analysis yielded prenatal MeHg curves similar to the linear analysis. For the regression tree analysis, the curves relating prenatal MeHg to outcomes between the 4 clusters differed and some crossed at higher prenatal MeHg levels, suggesting non-homogeneity in the upper range of exposure. Additionally, some of the curves suggested a possible non-linear relationship within the range of exposure we studied. This non-linear analysis supports the findings from the linear analysis. It shows little evidence to support an adverse association of prenatal MeHg exposure through maternal consumption of fish contaminated with natural background levels. However, the tree analysis suggests that the prenatal exposure/outcome relationship may not be homogeneous across all individuals and that some subpopulations may have an adverse association in the upper range of the exposures studied. More robust data in the higher levels of exposure in this cohort are needed to confirm this finding.  相似文献   

Predominant period and equivalent viscous damping ratio identification for a full‐scale building shake table test          下载免费PDF全文

Michelle C. Chen  Rodrigo Astroza  José I. Restrepo  Joel P. Conte  Tara Hutchinson  Yehuda Bock 《地震工程与结构动力学》2017,46(14):2459-2477

The predominant period and corresponding equivalent viscous damping ratio, also known in various loading codes as effective period and effective damping coefficient, are two important parameters employed in the seismic design of base‐isolated and conventional building structures. Accurate determination of these two parameters can reduce the uncertainty in the computation of lateral displacement demands and interstory drifts for a given seismic design spectrum. This paper estimates these two parameters from data sets recorded from a full‐scale five‐story reinforced concrete building subjected to seismic base excitations of various intensities in base‐isolated and fixed‐base configurations on the outdoor shake table at the University of California, San Diego. The scope of this paper includes all test motions in which the yielding of the reinforcement has not occurred and the response can still be considered ‘elastic’. The data sets are used with three system identification methods to determine the predominant period of response for each of the test configurations. One of the methods also determines the equivalent viscous damping ratio corresponding to the predominant period. It was found that the predominant period of the fixed‐base building lengthened from 0.52 to 1.30 s. This corresponded to a significant reduction in effective system stiffness to about 16% of the original stiffness. The paper then establishes a correlation between predominant period and peak ground velocity. Finally, the predominant periods and equivalent viscous damping ratios recommended by the ASCE 7‐10 loading standard are compared with those determined from the test building. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Shake table tests of unattached,asymmetric, dual‐body systems          下载免费PDF全文

C. E. Wittich  T. C. Hutchinson 《地震工程与结构动力学》2017,46(9):1391-1410

Systems of unattached, or freestanding, structures are highly vulnerable to damage and/or collapse during an earthquake, as evidenced during numerous past events. This class of structural system includes statue–pedestal systems, multidrum columns, radiation shields, unreinforced masonry walls, and other mechanical and electrical equipment. While a number of studies have analyzed the response of the single rocking block, very few have tested the response of multiple block systems subjected to earthquakes. Therefore, this paper details an extensive shake table testing campaign in which the seismic response of a pair of stiff, unattached blocks, herein referred to as a dual‐body system, was evaluated. Experimental variables include the geometry, including asymmetry, of both top (tower) and bottom (pedestal) bodies, input motion, and the coefficient of friction beneath the system. Furthermore, the tower structures were tested both in dual‐body configurations as well as in single‐body configurations allowing an understanding of the effect of the pedestal. The tests indicate that the presence of a pedestal increases the likelihood of collapse and amplitude of rocking demands, in general. However, certain geometric and interface combinations yield a more stable tower in a dual‐body configuration compared to a single‐body configuration, because of the dependence of the pedestal response on the geometry of the tower. Furthermore, a low‐friction interface beneath the pedestal reduces demands on the tower. However, this low‐friction interface may still transfer long‐period contributions of the input motion to the tower, which may be detrimental to its response. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献