The shape of the seismic response interaction diagram: The effect of combination rules in response spectrum analysis

This paper deals with the construction of seismic response interaction diagrams that show the correlation of multiple responses and are important to determine the critical combination of modal responses. Many design problems, such as column design under combined axial force and bending moments, fall into this category. We address general modal and multicomponent combination rules and study their effect on the shape of the response interaction diagrams, thus extending previous work done for quadratic combination rules. Special attention is given to multilinear combination rules which lead to polyhedral shapes. Having developed efficient methods to deal with polyhedral shapes, we explore the idea of adopting a multilinear modal combination rule to compose with a multicomponent percentage rule.     

Strict positive definiteness under axial symmetry on the sphere

Stochastic Environmental Research and Risk Assessment - Axial symmetry for covariance functions defined over spheres has been a very popular assumption for climate, atmospheric, and environmental...     

Environmental factors influencing aggregation of manta rays (Manta birostris) off the northeastern coast of the Yucatan Peninsula

Manta rays inhabit tropical, subtropical and temperate waters. Aggregation sites of manta rays have been recognized worldwide, but the reasons for this behavior are still poorly understood. This study describes environmental factors influencing aggregation sites of the giant manta ray (Manta birostris) off the northeastern coast of the Yucatan Peninsula. Observations of manta rays were obtained from scientific surveys conducted during 2006–2011. Environmental data were obtained from satellite imagery. The maximum entropy (Maxent) method for habitat modeling was used to determine the effects of environmental conditions on the species and predict suitable habitat for manta rays in this region. Primary productivity and distance to the coast were the most influential variables, suggesting that aggregation occurs in highly productive coastal waters. The distribution of manta rays predicted by the Maxent model showed that the most suitable habitat within the study area is located off the northeastern coast of the Yucatán Peninsula, more precisely, northeast of Isla Holbox and northwest of Isla Contoy. Seasonal patterns of distribution suggest that the most suitable conditions are present from July through September.     

Process-based forward numerical ecological modeling for carbonate sedimentary basins

Nowadays, numerical modeling is a common tool used in the study of sedimentary basins, since it allows to quantify the processes simulated and to determine interactions among them. One of such programs is SIMSAFADIM-CLASTIC, a 3D forward-model process-based code to simulate the sedimentation in a marine basin at a geological time scale. It models the fluid flow, siliciclastic transport and sedimentation, and carbonate production. In this article, we present the last improvements in the carbonate production model, in particular about the usage of Generalized Lotka-Volterra equations that include logistic growth and interaction among species. Logistic growth is constrained by environmental parameters such as water depth, energy of the medium, and depositional profile. The environmental parameters are converted to factors and combined into one single environmental value to model the evolution of species. The interaction among species is quantified using the community matrix that captures the beneficial or detrimental effects of the presence of each species on the other. A theoretical example of a carbonate ramp is computed to show the interaction among carbonate and siliciclastic sediment, the effect of environmental parameters to the modeled species associations, and the interaction among these species associations. The distribution of the modeled species associations in the theoretical example presented is compared with the carbonate Oligocene-Miocene Asmari Formation in Iran and the Miocene Ragusa Platform in Italy.     

A New Appraisal of Sri Lankan BB Zircon as a Reference Material for LA‐ICP‐MS U‐Pb Geochronology and Lu‐Hf Isotope Tracing

A potential zircon reference material (BB zircon) for laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) U‐Pb geochronology and Hf isotope geochemistry is described. A batch of twenty zircon megacrysts (0.5–1.5 cm³) from Sri Lanka was studied. Within‐grain rare earth element (REE) compositions are largely homogeneous, albeit with some variation seen between fractured and homogeneous domains. Excluding fractured cathodoluminescence bright domains, the variation in U content for all analysed crystals ranged from 227 to 368 μg g^?1 and the average Th/U ratios were between 0.20 and 0.47. The Hf isotope composition (0.56–0.84 g/100 g Hf) is homogeneous within and between the grains – mean ¹⁷⁶Hf/¹⁷⁷Hf of 0.281674 ± 0.000018 (2s). The calculated alpha dose of 0.59 × 10¹⁸ g^?1 for a number of BB grains falls within the trend of previously studied, untreated zircon samples from Sri Lanka. Aliquots of the same crystal (analysed by ID‐TIMS in four different laboratories) gave consistent U‐Pb ages with excellent measurement reproducibility (0.1–0.4% RSD). Interlaboratory assessment (by LA‐ICP‐MS) from individual crystals returned results that are within uncertainty equivalent to the TIMS ages. Finally, we report on within‐ and between‐grain homogeneity of the oxygen isotope systematic of four BB crystals (13.16‰ VSMOW).     

Aftershock seismic assessment taking into account postmainshock residual drifts

This paper introduces and evaluates a methodology for the aftershock seismic assessment of buildings taking explicitly into account residual drift demands after the mainshock (i.e., postmainshock residual interstory drifts, RIDR_o). The methodology is applied to a testbed four‐story steel moment‐resisting building designed with modern seismic design provisions when subjected to a set of near‐fault mainshock–aftershock seismic sequences that induce five levels of RIDR_o. Once the postmainshock residual drift is induced to the building model, a postmainshock incremental dynamic analysis is performed under each aftershock to obtain its collapse capacity and its capacity associated to demolition (i.e., the capacity to reach or exceed a 2% residual drift). The effect of additional sources of stiffness and strength (i.e., interior gravity frames and slab contribution) and the polarity of the aftershocks are examined in this study. Results of this investigation show that the collapse potential under aftershocks strongly depends on the modeling approach (i.e., the aftershock collapse potential is modified when additional sources of lateral stiffness and strength are included in the analytical model). Furthermore, it is demonstrated that the aftershock capacity associated to demolition (i.e., the aftershock collapse capacity associated to a residual interstory drift that leads to an imminent demolition) is lower than that of the aftershock collapse capacity, which mean that this parameter should be a better measure of the building residual capacity against aftershocks. Copyright © 2014 John Wiley & Sons, Ltd.     

NATURAL AND ANTHROPOGENIC FACTORS CONTROLLING GULLY EROSION IN THEBASALTIC UPLAND OF SOUTHERN BRAZIL

This paper describes an analysis of natural and anthropogenic factors controlling the evolution of gullies in a rural basin in the basaltic upland in the State of Rio Grande do Sul, Southern Brazil. In this region of deep ferrallitic soils with more than 60% clay, runoff and erosion are of increasing concern. In the TaboAo drainage basin （100 km^2）, gully erosion was studied in a field survey that measured rills and gullies. Eighty-four gullies were identified. They had an average length of 136 m, were 10 m wide, and 3 m deep and had a volume of 15.458 m3. Each gully was characterised in terms of factors that included slope, geological structure, presence of piping, drainage, soil use, and the presence of surface and subsurface flow. On average, the main channels had knickpoints varying from 2 m to 7 m, and their evolution in the vertical plane increased until bed-rock basalt material was reached, after which gullies increase in width and length. Gully development was also monitored from 1991 to 2003. Subsurface flow appears to be the principal agent controlling their development. Results show that both natural （slope, surface curvature, geological structure and rainfall） and anthropogenic （soil use, road construction） factors are important in gully development. The change in cultural practices throughout the drainage basin from conventional to direct seeding has led to increased subsurface flow, which was more important than surface runoff in causing erosion. However, the higher rainfall during E1 Nifio Southern Oscillation （ENSO） events and the consequently higher subsurface flow were the dominant factors. From 1991 to 2003 a total land loss of 1,013 m3 was observed in one gully, with 236 m^3 lost during the 1992 ENSO and 702 m3 during the 1997 ENSO; 95% of the total volume lost occurred during ENSO periods.     

Assessment of the effects of a marine urban outfall discharge on caged mussels using chemical and biomarker analysis

To assess the presence of endocrine disruptors in treated marine outfall discharges and their possible effects, mussels (Mytilus galloprovincialis) were caged in the environmental mixing zone of the outfall of the Santander sanitation system and in one control area. After 30, 60 and 90 days, samples were collected to perform chemical analyses (metals, anionic surfactants, alkylphenols, bisphenol A, phthalates and estrogenic hormones), biomarkers of general stress (lysosomal membrane stability-LMS, histopathology) and biomarkers of endocrine disruption (vitellogenin-like proteins and gonad index). There were no significant differences between outfall and control sites on contaminant levels, except for 4-tert-octylphenol which was higher in the outfall site. Bacteriological counts were higher in the outfall area. No relevant differences in biomarkers were detected between treated and control mussels. A significant reduction in LMS occurred in both groups after 90 days caging, indicating a stress situation possibly related to caging or to post-spawning reproductive state.     

Macrobenthic community for assessment of estuarine health in tropical areas (Northeast, Brazil): Review of macrofauna classification in ecological groups and application of AZTI Marine Biotic Index

The aim of the present study was to investigate the ecological quality of tropical estuaries on the northeastern coast of Brazil using the AMBI. Macrofauna classification based on ecological groups was reviewed using the Indicator Value (IndVal) coefficient. The results indicate that the ecosystems exhibit some level of disturbance. Most sites are situated between slightly-moderately disturbed boundaries due to the higher proportion of Nematoda (assigned here as Ecological Group I) and of Oligochaeta and Tubificidae (both classified as Ecological Group V). The AMBI proved efficient in evaluating environmental status, although the applicability of this index requires adjustments regarding some species in ecological groups. The present study also highlights the merits of the IndVal method for examining the assignments of species/taxa to an ecological group and demonstrates the validity of this coefficient is an assessment tool. Moreover, the complementary use of different methods is recommended for the assessment of ecosystem quality.