Mobilization analysis of the dolmen of Dombate (Northwest Spain)

This paper presents an analysis of the mobilization of the dolmen of Dombate, a megalithic monument situated in the Northwest of Spain. The study is founded on simple static principles, with the application of basic concepts of soil mechanics (soil reactions were computed by the reaction modulus method) and rock mechanics (a simple secant approach was adopted to model the contact between orthostats). In addition, a simplified geometric model for dolmens was adopted. On the basis of these concepts, a numerical solver able to provide quick estimations of the system's mobilization was developed. Using this tool, a number of sensitivity analyses were conducted to estimate the mobilization that could be caused by a conservation project currently under consideration. It was found that mobilization might be excessive, and therefore, a safer procedure is proposed. In short, this paper puts forth a new rational approach for archaeological practices which may help to estimate the possible consequences of excavations and rehabilitations on megalithic structures.     

Surface dynamic deformation estimates from local seismicity: the Itoiz reservoir,Spain

We analyze the ground motion time histories due to the local seismicity near the Itoiz reservoir to estimate the near-source, surface 3D displacement gradients and dynamic deformations. The seismic data were obtained by a semipermanent broadband and accelerometric network located on surface and at underground sites. The dynamic deformation field was calculated by two different methodologies: first, by the seismo-geodetic method using the data from a three-station microarray located close to the dam, and second, by single station estimates of the displacement gradients. The dynamic deformations obtained from both methods were compared and analyzed in the context of the local free-field effects. The shallow 1D velocity structure was estimated from the seismic data by modeling the body wave travel times. Time histories obtained from both methods result quite similar in the time window of body wave arrivals. The strain misfits between methods vary from 1.4 to 35.0 % and rotational misfits vary from 2.5 to 36.0 %. Amplitudes of displacement gradients vary in the range of 10^?8 to 10^?7 strains. From these results, a new scaling analysis by numerical modeling is proposed in order to estimate the peak dynamic deformations for different magnitudes, up to the expected maximum M _w in the region (M5.5). Peak dynamic deformations due to local M _w5.5 earthquakes would reach amplitudes of 10^?5 strain and 10^?3 radians at the Itoiz dam. The single station method shows to be an adequate option for the analysis of local seismicity, where few three-component stations are available. The results obtained here could help to extend the applicability of these methodologies to other sites of engineering interest.     

Geostrophic Adjustment Problems in a Polar Basin

The geostrophic adjustment of a homogeneous fluid in a circular basin with idealized topography is addressed using a numerical ocean circulation model and analytical process models. When the basin is rotating uniformly, the adjustment takes place via excitation of boundary propagating waves and when topography is present, via topographic Rossby waves. In the numerically derived solution, the waves are damped because of bottom friction, and a quasi-steady geostrophically balanced state emerges that subsequently spins-down on a long time scale. On the f-plane, numerical quasi-steady state solutions are attained well before the system's mechanical energy is entirely dissipated by friction. It is demonstrated that the adjusted states emerging in a circular basin with a step escarpment or a top hat ridge, centred on a line of symmetry, are equivalent to that in a uniform depth semicircular basin, for a given initial condition. These quasi-steady solutions agree well with linear analytical solutions for the latter case in the inviscid limit.

On the polar plane, the high latitude equivalent to the β-plane, no quasi-steady adjusted state emerges from the adjustment process. At intermediate time scales, after the fast Poincaré and Kelvin waves are damped by friction, the solutions take the form of steady-state adjusted solutions on the f-plane. At longer time scales, planetary waves control the flow evolution. An interesting property of planetary waves on a polar plane is a nearly zero eastward group velocity for the waves with a radial mode higher than two and the resulting formation of eddy-like small-scale barotropic structures that remain trapped near the western side of topographic features.

RÉSUMÉ?Traduit par la rédaction] Nous étudions l'ajustement géostrophique d'un fluide homogène dans un bassin circulaire ayant une topographie idéalisée à l'aide d'un modèle numérique de circulation océanique et de modèles analytiques de processus. Quand le bassin est en rotation uniforme, l'ajustement se fait par l'excitation d'ondes de propagation aux limites, et en présence de topographie, par des ondes de Rossby topographiques. Dans la solution numériquement dérivée, les ondes sont amorties à cause frottement contre le fond, et un état quasi-stable géostrophiquement équilibré s’établit pour ensuite décélérer sur une longue période de temps. Sur le plan f, les solutions numériques d’états quasi-stables sont atteintes bien avant que l’énergie du système mécanique soit entièrement dissipée par le frottement. Nous démontrons que les états ajustés apparaissant dans un bassin circulaire avec un accore en forme de marche ou une crête en forme de merlon, centrés sur une ligne de symétrie, sont équivalents à ceux d'un bassin semi-circulaire de profondeur uniforme pour une condition initiale donnée. Les solutions quasi-stables s'accordent bien avec les solutions analytiques linéaires pour le dernier cas dans la limite de la non-viscosité.

Sur le plan polaire, la haute latitude équivalente au plan β, le processus d'ajustement n'aboutit à aucun état ajusté quasi-stable. Aux échelles de temps intermédiaires, après l'amortissement des ondes rapides de Poincaré et Kelvin par le frottement, les solutions prennent la forme de solutions ajustées d’états stables sur le plan f. Aux échelles de temps plus longues, les ondes planétaires déterminent l’évolution de l’écoulement. Une propriété intéressante des ondes planétaires sur un plan polaire est une vitesse de groupe presque nulle vers l'est pour les ondes ayant un mode radial plus grand que deux et la formation résultante de structures barotropiques de petite échelle de type remous qui demeurent emprisonnées près du bord ouest des caractéristiques topographiques.     

A smoothed ANOVA model for multivariate ecological regression

Smoothed analysis of variance (SANOVA) has recently been proposed for carrying out disease mapping. The main advantage of this approach is its conceptual simplicity and ease of interpretation. Moreover, it allows us to fix the combination of diseases of particular interest in advance and to make specific inferences about them. In this paper we propose a reformulation of SANOVA in the context of ecological regression studies. This proposal considers the introduction in a non-parametric way of one (or several) covariate(s) into the model, explaining some pre-specified combinations of the outcome variables. In addition, random effects are also incorporated in order to model geographical variation in the combinations of outcome variables not explained by the covariate. Lastly, the model permits the decomposition of the variance in the set of outcome variables into different orthogonal components, quantifying the contribution of every one of them. The proposed model is applied to the geographical analysis of mortality due to malignant stomach neoplasm among women resident in the city of Barcelona (Spain). The available outcome variables are deaths grouped into two time periods, and a socioeconomic deprivation index is included as a covariate. The model has been implemented through INLA, a novel inference tool for Bayesian statistics.     

How much does an extreme rainfall event cost? Material damage and relationships between insurance,rainfall, land cover and urban flooding

This research aims to understand how insurance, rainfall, land cover and urban flooding are related and how these variables influenced the material damage in the Lisbon Metropolitan Area (LMA) during the 2000–2011 period. Correlation coefficients show strong relationships between built-up areas and claims (0.94) and payouts (0.88). Despite no significant relationships being found between rainfall and the amount of material damage per event, three likelihood levels of flooding were determined for hourly rainfall. Unlike the studied period, the number of claims and their spatial distribution during the 2008 extreme rainfall event were strongly dependent on rainfall. Flooding related to the old watercourses assumed greater importance during this extreme event, recovering a more natural/ancient hydrological behaviour. In the LMA, the greatest material damage was the result of high-magnitude/low-probability rainfall events. Lower magnitude events can trigger numerous claims in heavily built-up areas, but they are hardly capable of producing large material damage.     

Field investigation of siltation at a tidal harbor: North Port of Incheon,Korea

Ocean Dynamics - To understand siltation processes within the North Port of Incheon, Korea, this study estimated the sedimentation rate and then determined the dominant mechanisms for the...     

Model prediction capacity of ephemeral gully evolution in conservation tillage systems

Ephemeral gully (EG) erosion has an important impact on agricultural soil losses and increases field surface hydrology connectivity and transport of pollutants to nearby water bodies. Watershed models including an EG component are scarce and not yet properly evaluated. The objective of this study is to evaluate the capacity of one such tool, AnnAGNPS, to simulate the evolution of two EG formed in a conservation tillage system. The dataset for model testing included runoff measurements and EG morphological characteristics during 3 years. Model evaluation focused on EG evolution of volume, width, and length model outputs, and included calibration and testing phases and a global sensitivity analysis (GSA). While the model did not fully reproduce width and length, the model efficiency to simulate EG volume was satisfactory for both calibration and testing phases, supporting the watershed management objectives of the model. GSA revealed that the most sensitive factors were EG depth, critical shear stress, headcut detachment exponent coefficient b, and headcut detachment leading coefficient a. For EG outputs the model was additive, showing low sensitivity to interactions between the inputs. Prediction of EG spatial evolution on conservation tillage systems requires improved development of gully erosion components, since many of the processes were developed originally for traditional tillage practices or larger channel systems. Our results identify the need for future research when EG form within conservation tillage systems, in particular to study gully headcut, soil erodibility, and width functions specific to these practices.     

Investigating the presence of organochlorine pesticides and polychlorinated biphenyls in wild and farmed gilthead sea bream (Sparus aurata) from the Western Mediterranean sea

The presence of organochlorine pesticides and polychlorinated biphenyls in wild and farmed gilthead sea bream (Sparus aurata) from the Western Mediterranean, Spain, is investigated. These pollutants were determined in white and red muscle and liver by gas chromatography coupled to tandem mass spectrometry. Contaminant profiles present in both wild and farmed fish tissues include DDTs, PCBs and HCB. The highest concentrations of contaminants were found in liver, and an increase in pollutant levels was observed in autumn, before spawning. This fact is explained in light of increased food intake when sea water temperatures increase. Gilthead sea bream from Western Mediterranean populations showed significantly higher concentrations of DDTs and PCBs than farmed fish from the same area. This fact is attributed to the low level of organochlorine contaminants present in fish feed supplied to the cultured fish. The diet is highlighted as an important factor in understanding differences observed in organochlorine pollutants levels of fish tissues.     

Inshore/offshore gradients of imposex and organotin contamination in Nassarius reticulatus (L.) along the Portuguese coast

Imposex and organotin (OT) tissue contamination of the netted whelk Nassarius reticulatus (L.) were assessed in the continental shelves around the main estuaries of the central coast of Portugal (Lisbon: Tagus estuary; Setúbal: Sado estuary) and the main coastal lagoon in the Southern of Portugal (Faro: Ria Formosa). Pollution levels were higher in areas of more intense boat traffic and shipyard activities and imposex showed a clear decreasing gradient from the estuaries to the offshore, in relation to a similar gradient of tissue contamination by tributyltin. Remarkably, imposex was extensively spread over the adjacent continental shelves of Tagus and Sado estuaries. The current work shows that TBT pollution is undoubtedly a matter of concern not only for the above estuaries where harbours are implanted but also for the adjacent continental shelves, regardless the massive dilution of contaminants that may occur in these deeper areas.