• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 40
  • 20
  • 11
  • 4
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 104
  • 18
  • 14
  • 13
  • 13
  • 12
  • 12
  • 11
  • 11
  • 10
  • 10
  • 10
  • 10
  • 10
  • 9
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Emprego de dados gravimétricos e de altimetria por satélite como subsídio à análise morfoestrutural na região da Bacia de Pelotas - Rio Grande do Sul

Gagg, Gilberto January 2014 (has links)
Dados de gravimetria e de altimetria por satélite foram usados como subsídio à análise morfoestrutural na região da Bacia de Pelotas-RS. Na abordagem gravimétrica foi usado o modelo geopotencial EGM2008 através das anomalias Bouguer e na abordagem batimétrica foi usado o modelo global DTU10BAT. Através dos mapas de anomalias Bouguer e perfis gravimétricos gerados, verificou-se que as anomalias Bouguer aumentam positivamente da costa em direção às maiores profundidades oceânicas, o que caracteriza um progressivo afinamento crustal associado à deriva continental. O comportamento das anomalias Bouguer obtidas por dados satelitais evidenciaram a presença de uma ruptura conhecida como Charneira Albo-aptiana na plataforma continental. A incidência de valores de anomalias significativamente positivas na região do Baixo de Mostardas sugere a presença de uma massa de maior densidade nesta região. A resolução dos dados gravimétricos utilizados não permitiu evidenciar a presença de paleocanais na região, sendo necessária uma maior resolução espacial, associada a outros métodos de investigação. O uso de dados de altimetria por satélite (modelo DTU10BAT) permitiu a análise batimétrica da plataforma continental e a investigação da configuração morfológica da região, que foi dividida em três faixas: Torres- Farol Solidão, Farol Solidão-Farol da Conceição e Farol da Conceição-Farol Sarita. Foi gerado um modelo teórico e comparado com o modelo DTU10BAT na geração do mapa de anomalias batimétricas. Os eixos de anomalias batimétricas negativas identificados estão frequentemente associados à direção de paleodrenagens, assim como as anomalias positivas tem relação com linhas de paleoestabilizações do nível do mar ou altos estruturais. Foi definida uma sequência de descontinuidades na altura do Farol da Conceição que apresentou expressiva coincidência com paleocanais delineados na mesma região através de outros estudos. Todos os dados foram processados e integrados em um sistema de informações geográficas. Os dados gravimétricos e batimétricos oriundos de missões satelitais são uma grande ferramenta nos estudos regionais para áreas que envolvam aplicações geológicas e mesmo oceanográficas. / Data from satellite altimetry and gravity were used to the morphostructural analysis in the Pelotas Basin-RS region. The EGM2008 geopotential model through the Bouguer anomalies was used in the gravimetric approach and the DTU10BAT global model was used in the bathymetric approach. Through the Bouguer anomalies maps and the gravimetric profiles that were generated, it was observed that Bouguer anomalies increase positively from coast towards to the major ocean depths, what characterizes a progressive crustal thinning associated with the continental drift. The behavior of the Bouguer anomalies obtained from satellite data showed the presence of a rupture, known as Charneira Albo-Aptiana, on the continental shelf. The incidence of significant positive anomalies values on the Baixo de Mostardas region suggests the presence of a higher-density mass in this region. Because of the resolution of the gravimetric data used in this research was not enough, it was not possible to show the presence of paleochannels in the region, requiring a greater spatial resolution data, associated with other methods of investigation. The use of satellite altimetric data (model DTU10BAT) allowed the bathymetric analysis of the continental shelf and the research of morphological configuration of the region, which was divided into three areas: Torres- Solidão Lighthouse, Solidão Lighthouse-Conceição Lighthouse and Conceição Lighthouse-Sarita Lighthouse. A theoretical model was generated and it was compared with the DTU10BAT model in the generation of the bathymetric anomalies map. The axes of negative bathymetric anomalies identified are often associated with the direction of paleochannels, as well as the positive anomalies are related to lines of sea level paleostabilizations or structural highs. It was defined a sequence of discontinuities at the Conceição Lighthouse proximities which presented a significant coincidence with paleochannels that were delineated in the same region through other studies. The data were processed and integrated in a geographic information system. Gravimetric and bathymetric data from satellite missions are an important tool in regional studies for areas that involve geological and oceanographic applications.
72

Sedimentation in a small lake, more complex than previously assumed. : Bathymetrical and geochemical sediment analyses in Kassjön (63°55´ N, 20°01´ E).

Gydemo Östbom, Viktor January 2017 (has links)
For studies using lake sediments as a medium, understanding factors governing sediment distribution and properties is crucial for making accurate interpretations and conclusions. General lake sedimentation theory is however mainly based on larger lakes and systems, potentially leading to biased sampling and data interpretation when applied on a smaller system. In a paper published in 2008, Rippey et al. evaluated the fit of some general sedimentation theories on element distribution in the sediments of Kassjön (63°55´ N, 20°01´ E), northern Sweden. This small boreal lake reoccurs in the scientific literature, largely from paleolimnological studies on varved sediments in the lake, making the understanding of its sediment properties highly relevant. As part of a wider geochemical study on the lake, this paper scrutinizes the findings of Rippey et al. (2008) by using updated bathymetry and geochemical analyses, to provide further insight on sedimentation in Kassjön. Element composition, analysed with X-ray fluorescence spectrometry, and dry weight was obtained from sediment samples at 40 sites. Depth at sampling sites, together with catchment morphometry and previous bathymetry, was used to improve the bathymetric understanding. Kassjön was found to have a less steep bathymetry than previously assumed, with distribution of sediment geochemistry and dry weight showing heterogeneity differing from that expected of general sedimentation theories only. These results indicate that previous findings on sedimentation in Kassjön might be too simplistic, and that small-lake sedimentation is influenced by factors not included in general sedimentation models. Caution is therefore advised when e.g. interpreting the environmental record in lake sediments.
73

Tidally Generated Internal Waves from Dual-Ridge Topography

Sanderson, Ian Derik 01 November 2022 (has links)
Internal waves are generated in stratified fluids, like the ocean, where density increases with depth. Tides are one of the major generation mechanisms of internal waves. As the tides move water back and forth over underwater topography, internal waves can be generated. Topography slope and amplitude are major factors in the behavior of the generated internal wave field. In order to further understand the effects topographic shape plays, the effect of asymmetry on internal waves is investigated. This research investigates internal waves generated by dual-ridge topographies. Four cases of symmetric topographies, T, M, W, and W2, with three different peak spacings are compared to their singular ridge counter parts at three oscillation frequencies, ω = 0.6N, ω = 0.75N, and ω = 0.9N. Both subcritical and supercritical symmetric ridges were investigated. Experiments were also performed for subcritical, asymmetric dual ridges at the middle oscillation frequency. The internal wave fields were captured with synthetic schlieren and analyzed with the Hilbert transform and sum of kinetic energy in wavenumber space. It is found that for wave fields from substantially separated ridges, mixing and wave interference occurs that decreases total kinetic energy of the system.
74

Micro-XRF geochemical and micropaleontological evidence for prehistoric land disturbance, Serpent Mounds complex, Rice Lake (Ontario, Canada)

Pringle, Tynan 05 1900 (has links)
This thesis represents the first example of a pre-agricultural, pre-colonial land disturbance event in the archaeological record of North America. It demonstrates the critical importance of multivariate analysis and µ-XRF core scanning in determining precise chronologies for episodes of heightened clastic input from soil erosion, enhanced by human occupation, shellfish harvesting, and burial mound construction. / Serpent Mounds is a prehistoric (Middle Woodland Period, ca. 2000--1000 BP) burial mound complex located on the north shore of Rice Lake, in southern Ontario, Canada. The complex includes a 60m long and 10m wide sinuous earthwork ridge interpreted as a serpent effigy and eight smaller oval mound structures. Archaeological excavations determined seasonal site occupation for harvesting wild rice and shellfish and conducting mortuary rites. The timing of mound construction and site occupation is poorly constrained by limited radiocarbon dates, restricted to burials. The site is of high cultural importance as the only known effigy mound structure in Canada and is a sacred First Nations burial ground; thus all investigation must employ non-invasive techniques. High-resolution XRF Core Scanning and micropaleontologic analysis (testate amoebae) of 12 lake sediment cores was employed to investigate the timing of mound construction, and assess geochemical records of prehistoric land disturbance. Land disturbance is indicated by increased sediment flux, by rising abundance of minerogenic elements (K, Ti, Zr, Si, Fe) within a distinctive silt-rich gyttja unit. The event is also recorded in the thecamoebian assemblage, which is dominated by indicators of a eutrophic, turbid lake environment. Principal Component Analysis and Cluster Analysis of µ-XRF data identify distinctive chemofacies across several cores. AMS 14C dates for the prehistoric land disturbance episode correspond with the Point Peninsula occupation, indicating a protracted occupation period of \textasciitilde 750 years (2050 - 1300 cal BP) with two major peaks in soil erosion at 1900 and 1450 cal BP. The sedimentation rate (>1.5mm/yr) during the Middle Woodland phase of enhanced erosion was comparable to that during the 1838 CE dam construction at Hastings. The reconstructed Middle Woodland paleoshoreline and water levels indicate a shallow lake and wetland environment, with viable habitats for wild rice stands and shellfish resources. The results demonstrate that XRF Core Scanning and micropaleontological methods are important for the investigation of culturally-sensitive archaeological sites, including sacred burial grounds where conventional archaeological excavation cannot be undertaken. / Thesis / Master of Science (MSc) / Serpent Mounds is a prehistoric (Middle Woodland Period, ca. 2000 - 1000 BP) burial mound complex located in Rice Lake, Ontario. Archaeological excavation (1897 - 1970) determined the site was occupied by people of the Point Peninsula culture (ca. 2200 - 1350 BP) on a seasonal basis, for burial rites and shellfish gathering. Many questions remain with regard to the date of mounds construction, how long the site was occupied, and how occupation and construction activities impacted the local environment. The site has been designated as a National Historical Site and excavation is no longer permitted in the interest of site preservation and cultural value to First Nations. This study investigated the history of environmental changes associated with prehistoric indigenous and European land use changes using minimally-invasive methods, including sonar bathymetric mapping, XRF Core Scanning and microfossil analysis of lake sediment cores. Sonar data were employed to map the lake bottom relief (bathymetry) and to reconstruct past changes in lake levels and shoreline positions. µ-XRF methods measures changes in elemental abundance in lake core samples to identify human occupation phases and land disturbance. Microfossils (testate amoebae) track the ecosystem response to environmental changes associated with human occupation. The geochemical and microfossil data identified an interval of increased sediment delivery to Rice Lake, coinciding with the arrival of Point Peninsula peoples. The land disturbance is recognized in cores by an increase in zirconium (Zr), titanium (Ti) and other soil-derived elements. During this phase, lake levels rose gradually, wetlands expanded and wild rice was abundant resource available to indigenous peoples. Following European colonization in the 1820’s, and the construction of the Hastings Dam (1838 CE), lake levels increased rapidly by over \SI{2}{\metre}, causing a shift to a more nutrient-rich (eutrophic) lake environment and a decline in wild rice stands. Soil erosion associated with European land clearance is recorded by in a dramatic increase in the abundance of soil-derived elements.
75

Hydrologický režim vybraných jezer Vysokých Tater / Hydrological regime of selected lakes in the High Tatra Mts.

Sankotová, Tereza January 2015 (has links)
This diploma thesis deals with morphometric analysis and hydrological regime of Skalnaté pleso lake and Hincové Oká lakes, especially the lake level fluctuation, during the period 2011 - 2014. One of the tasks was the bathymetric mapping of observed locations. For Hincové Oká lakes was it the first mapping of bathymetry at all. The hydrological regime and lake level fluctuation regime of observed locations shows interesting differences from the other Tatra lakes whose hydrological regime is controlled by precipitation amounts. The annual culmination of Hincové Oká lakes (the largest lake) is shifted into the spring caused by melting snowpack. When there is no rainfall for a couple of days Skalnaté pleso lake often dries up, even during summer months, when levels of most Tatra lakes reach their maximum values. However summer drying is shortterm. Lake level fluctuation regime is very dynamic. After a strong rainfall event its level rises very steeply, up to 0,14 m per hour. Powered by TCPDF (www.tcpdf.org)
76

[en] GEOENVIRONMENTAL CHARACTERIZATION OF JACAREPAGUÁ LAGOON SEDIMENTS - RJ / [pt] CARACTERIZAÇÃO GEOAMBIENTAL DOS SEDIMENTOS DA LAGOA DE JACAREPAGUÁ - RJ

PAULA ELIAS BENEDETTI 11 June 2019 (has links)
[pt] A presente dissertação tem como objetivo realizar um levantamento sobre o relevo de fundo, o tipo de material e a qualidade dos sedimentos quanto a contaminação, da Lagoa de Jacarepaguá, Rio de Janeiro, para auxiliar os programas ambientais de revitalização do Complexo Lagunar da Baixada de Jacarepaguá, que estão sendo desenvolvidos na área, focando as Olimpíadas de 2016. Na primeira etapa realizou-se a batimetria da Lagoa. Foram adquiridas profundidades georreferenciadas em campo e gerados modelos batimétricos em 2 e 3 dimensões, nos quais foram identificadas cavidades e um platô de baixa profundidade no interior da Lagoa. Na segunda etapa foram coletadas amostras de sedimentos da Lagoa, em variadas profundidades, para os ensaios da caracterização geotécnica. Com estes resultados identificou-se a presença predominante de 2 tipos de sedimentos, arenosos localizados no platô raso e siltosos nas cavidades, e alto teor de matéria orgânica e baixa densidade nas amostras siltosas. Complementarmente, foram ensaiadas duas amostras arenosas para determinação dos parâmetros de permeabilidade e de resistência ao cisalhamento, visando gerar dados adicionais para possível aproveitamento deste material como aterro, caso dragado. Na terceira, e última etapa, foi realizada uma nova coleta de sedimentos, para análise química dos metais Bário, Cádmio, Chumbo, Cobre, Cromo, Ferro, Manganês, Mercúrio, Níquel e Zinco e Hidrocarbonetos Policíclicos Aromáticos (HPA’s), cujos resultados indicaram uma acumulação de alguns metais na área de influência de deságüe do Arroio Pavuna. Concatenando os resultados obtidos nas 3 etapas, considerase necessário e emergencial o cessamento das descargas de efluentes, nos rios afluentes à Lagoa, e a dragagem do sedimento arenoso localizado no platô, resultando em um canal central mais profundo, um aumento da coluna d’água que implicará no melhoramento do fluxo de troca de água entre a Lagoa e o mar, acelerando a recuperação do ecossistema lagunar de uma forma geral. / [en] The present dissertation aims at conducting a survey on the bottom morphology, the material type and quality of sediment contamination, in the Jacarepaguá Lagoon, Rio de Janeiro, to assist the environmental programs working on the revitalization the Lagoon area, focusing on the 2016 Olympics. In the first stage the bathymetry of the Lagoon was executed. Georeferenced depth measurements were acquired in the field and bathymetric models in 2 and 3 dimensions were generated, where cavities and a shallow plateau inside the Lagoon were identified. In the second stage, sediment samples of the Lagoon were collected - from varied depths - for the geotechnical characterization tests. Based on the results, the presence of two predominant types of sediments was identified, sandy sediments located on the shallow plateau and silty sediments on the cavities, as well as high content of organic matter and low density in silty samples. In addition, two sandy samples were tested to determine the permeability and shear strength parameters in order to gather additional data for possible use of this material in civil construction (if dredged). In the third and final stage new sediment samples were collected for chemical analysis of the metals Barium, Cadmium, Lead, Copper, Chromium, Iron, Manganese, Mercury, Nickel and Zinc as well as Polycyclic Aromatic Hydrocarbons (PAH s). The results indicated an accumulation of some metals in the drainage area of the Pavuna Creek. Concatenating the results obtained in these three stages, it is considered necessary and urgent to stop the effluent discharges into the Lagoon s tributary rivers as well as to dredge the sandy sediment located in the plateau, that would result in a deeper central channel, an increase of water column leading to an improved flow of water exchange between the Lagoon and the sea, accelerating the recovery of the Lagoon s ecosystem in general.
77

Etude de la géométrie, de la nature et des déformations de la zone de subduction des Petites Antilles du Nord / Deep structure geometry, crust nature and tectonic deformation in the northern Lesser Antilles margin

Laurencin, Muriel 17 November 2017 (has links)
Dans les zones de subduction, la géométrie du slab est l'un des paramètres qui contrôle les déformations tectoniques de la marge, le couplage et le potentiel sismogénique. La subduction des Antilles résulte du chevauchement de la plaque Caraïbe vers le NE sur les plaques Amériques, à une vitesse de convergence de 2 cm/an. La sismicité est hétérogène et augmente localement sous la plateforme des Iles Vierges. D’une obliquité croissante vers le nord, cette zone est favorable à un partitionnement dont les déformations sont très peu observées. Ces travaux ont permis de confirmer un substratum d’une affinité de croûte océanique épaissie par un panache mantellique et faiblement épaissi par le magmatisme formant les arcs volcaniques Deux structures accommodant le partitionnement de la déformation ont été mis en évidence. La faille de Bunce est une faille décrochante sénestre de 850 km s’étendant d’Hispaniola jusqu’à Barbuda découplant le prisme d’accrétion du substratum. Le Passage d’Anegada, dont nous avons découvert son extension vers le NE, entaille profondément l’avant-arc. Formé par extension due à la collision du Banc des Bahamas sur le nord de la marge caribéenne, ces structures sont réactivées en décrochement sénestre compatible avec du partitionnement. Les caractéristiques d’une dorsale lente (core complexe et grain océanique) entrant en subduction sont imagées pour la première fois. Elles affectent probablement la morphologie du prisme d’accrétion et le potentiel sismogène. Là où les séismes et les déformations de partitionnement (Passage d’Anegada) s'accentuent localement, le slab est moins profond. Ainsi, le couplage interplaque pourrait augmenter localement et favoriser l'activité sismique et le partitionnement tectonique sous le Passage d'Anegada. / In subduction zones, the 3D geometry of the plate interface is one of the key parameters that controls margin tectonic deformation, interplate coupling and seismogenic behavior. The North American plate subducts below the Caribbean plate with a convergence rate of 20 mm/y. The seismic activity is heterogeneous and increases locally under the Virgin Islands platform. The northward increasing convergence obliquity is favorable in partitioning which deformations were not really observed. This PhD confirms that the forearc crust is a crust of oceanic affinity thickened by hotspot magmatism and poorly affected by subduction magmatism. Two structures accommodating the partitioning of the deformation were identified. The Bunce Fault is a 850-kmlength sinistral strike-slip fault extending from Hispaniola to the east of Barbuda decoupling the accretionary prism from the Caribbean substratum. The Anegada Passage, whose extension towards the NE is highlighted, entailed deeply the forearc. The structures are reactivated in sinistral strike-slip faults compatible with the partitioning of the deformation after formation in extension due to the collision of the Bahamas Bank with the northern margin. We image for the first time the characteristics of a slow ridge formation (partly complex core and partly oceanic grain) entering in subduction. It affects the morphology of the accretion prism and probably the seismogenic potential of the subduction interface. We have highlighted a shallower slab which is located under the NE Anegada Passage and where earthquakes and partitioning deformations increase locally. Thus, the shallowing slab might results in a local greater interplate coupling favoring seismic activity and tectonic partitioning beneath the Anegada Passage.
78

CONSERVATION LIMNOGEOLOGY AND BENTHIC HABITAT MAPPING IN CENTRAL LAKE TANGANYIKA (TANZANIA)

Lucas, Joseph S. 01 January 2018 (has links)
Small scale protected zones are valuable for helping the health and productivity of fisheries at Lake Tanganyika (East Africa). Spatial placement of protected areas relies on accurate maps of benthic habitats, consisting of detailed bathymetry data and information on lake-floor substrates. This information is unknown for most of Lake Tanganyika. Fish diversity is known to correlate with rocky substrates in ≤ 30 m water depth, which provide spawning grounds for littoral and pelagic species. These benthic habitats form important targets for protected areas, if they can be precisely located. At the NMVA, echosounding defined the position of the 30-m isobath and side-scan sonar successfully discriminated among crystalline basement, CaCO3-cemented sandstones, mixed sediment, and shell bed substrates. Total area encompassed from the shoreline to 30 m water depth is ~21 km2 and the distance to the 30-m isobath varies with proximity to deltas and rift-related faults. Total benthic area defined by crystalline basement is ~1.6 km2, whereas the total area of CaCO3-cemented sandstone is 0.2 km2. Crystalline basement was present in all water depths (0-30 m), whereas CaCO3-cemented sandstones were usually encountered in water ≤ 5 m deep. Spatial organization of rocky substrates is chiefly controlled by basin structure and lake level history.
79

Neotectonics, Seismic and Tsunami Hazards, Viti Levu, Fiji.

Rahiman, Tariq Iqbal Hamid January 2006 (has links)
Viti Levu, the main island of Fiji, is located in a seismically active area within the Fiji Platform - a remnant island arc that lies in a diffuse plate boundary zone between the Pacific and Australian tectonic plates in the southwest Pacific. The southeast coast of Viti Levu is a highly developed and populated part of Fiji and is vulnerable to the effects of large earthquakes that are expected to occur both onshore and offshore. The structural framework and the origin of seismicity within the Fiji Platform, as well as the seismic and tsunami hazards of central and southeast Viti Levu are investigated. The upper crust of southeast Viti Levu is dissected by several intersecting fault/lineament zones. These are mapped from remote sensing imagery of the surface (topography, radar, and aerial photos) and of the basement (magnetic), and have been subject to rigorous statistical tests of reproducibility and verification with field mapped fault data. Lineaments on the various imagery correlate with faults mapped in the field and show spatial continuity between and beyond mapped faults, thereby providing a fuller coverage of regional structural patterns than previously known. Some fault/lineament zones extend beyond the coastline to the offshore area of southeast Viti Levu. Here high resolution SeaBAT 8160 multibeam bathymetry data and seismic reflection data show that the fault zones occur along, and exert control on the locations of a number of linear submarine canyons. The morpho-structural expression of these canyons are contiguous with fault controlled physiographic features mapped on the nearshore marginal shelf (rectilinear bays and peninsulas, reef passages) and on land (fault valleys, slope and drainage alignments forming lineaments). The canyons are considered to have developed from several cycles of downslope incising and infilling events, whilst their positions were still primarily controlled by zones of weakness created by the fault zones. The principal fault sets in southeast Viti Levu represent generations of regional tectonic faulting that pervaded the Fiji Platform during and after disruption of the proto Fijian arc in the Middle to Late Miocene. These fault sets combine to form a complex network of interlocking faults creating a fault mesh that divides the upper crust into a number of fault blocks ranging from ~2 to 30 km. It is inferred that the fault mesh evolved throughout the Neogene as a response to the anticlockwise rotation of the Fiji Platform through progressive development of different fault sets and intervening crustal block rotations. Regional tectonic deformation is presently accommodated in a distributed manner through the entire fault mesh. Low magnitude earthquakes (<M4) occur regularly and may represent ruptures along short linking segments of the fault mesh, while infrequent larger earthquakes (>M4) may result from complex rupture propagation through several linking fault segments of the mesh that lie close to optimum stress orientations. This interpreted model of distributed deformation through the fault mesh for southeast Viti Levu is inferred to be characteristic of the style of active deformation that occurs throughout the entire Fiji Platform. Seismic activity is primarily responsible for triggering submarine landslides that occur on the southeastern slope of Viti Levu. These slides typically occur on the outer barrier reef edge, as well as in submarine canyon heads and walls, and in the mid slope areas. They are characteristically translational and lack bathymetric evidence for displaced masses. Morphometric analysis and empirical modelling, show that slides triggered at shallow water depths, within 5 km of the coastline, at the outer barrier reef edge and submarine canyon heads, produce the largest near-field tsunami amplitudes. Such slides are interpreted to represent a significant local tsunami hazard. A detailed case study of the destructive 1953 Suva tsunami that followed the Ms 6.75 Suva earthquake, reveals that the source of this tsunami was a 60 million cubic metre submarine landslide at the head of the Suva Canyon, 4 km to the WSW of Suva City. A test simulation of this tsunami using the Geowave tsunami generation, propagation and inundation model, closely replicates the wave heights and arrival times recorded in 1953. This simulation also reveals that high variability in tsunami impact over short coastal distances of southeast Viti Levu is attributable to the complex interplay of wave propagation with the barrier reef system, erratic lagoon bathymetry and the irregularly shaped coastline. A predictive simulation using Geowave, based on an incipient failure in the 1953 source area and on a potentially worse case scenario event at or near high-tide, is used to show a maximum vertical run up of at least 4 m and a maximum horizontal inundation level of at least 400 m at the Suva coast. The seismic hazard of five sites on Viti Levu, including Suva City, Navua and Nausori Towns, and the Monsavu and Nadarivatu dam sites, is evaluated using a deterministic approach, and seven newly identified crustal fault earthquake source structures. The maximum magnitudes interpreted for these structures, estimated using empirical relationships, range from Mw 6.8 to 7.6. The Suva Canyon Fault, the Naqara Fault, the Mavuvu/Fault Lineament Zone and the Nasivi Fault provide the controlling maximum credible earthquakes (CMCE) at all the five sites. The CMCE peak ground acceleration values for Suva City range from 0.4g to 0.6g, for Nausori Town from 0.18g to 0.2g, for Navua Town from 0.27g to 0.32g, for Monasavu from 0.39g to 0.42g, and for Nadarivatu from 0.23g to 0.33g. The horizontal spectral accelerations at a period equal to 0.2 seconds, calculated using the CMCEs, are comparable to accelerations derived by probabilistic methods that have return periods between 50 and over 1000 years.
80

Caracteriza??o batim?trica e fisicooceanogr?fica do canal de acesso ao porto de Cabedelo/PB: uma an?lise ambiental ao derrame de ?leo

Fraz?o, Luciana de Sousa 30 June 2011 (has links)
Made available in DSpace on 2014-12-17T14:08:45Z (GMT). No. of bitstreams: 1 LucianaSF_DISSERT.pdf: 4631139 bytes, checksum: 00137f0bba4f12c4fb23f7fee30c065d (MD5) Previous issue date: 2011-06-30 / The State of Para?ba is one of the most dynamic states of Brazil, strategically located in the northeast, is notable for the excellent potential for integration of different transportation modes forming the states of Rio Grande do Norte, Pernambuco and Alagoas. The dynamic that occurs with port activity causes changes in the space where it is installed. And the elements of this space are always more than suffering direct or indirect influences as the flow in the port is expanded. Therefore, this region became subject to the accidental spillage of oil, because it presents a heavy traffic of ships of various sizes that can run aground or collide with oil causing accidental events. The study of geomorphological and sedimentological compositions of seafloor becomes important as more is known about the relationships between these parameters and associated fauna, and can identify their preferred habitats. The database background, acoustically collected along the proposed study area, is a wealth of information, which were duly examined, cataloged and made available. Such information can serve as an important tool, providing a geomorphological survey of the sedimentary area studied, and come to subsidize, in a flexible, future decision making. With the study area Port of Cabedelo, Para?ba - Brazil, this research aimed to evaluate the influence of the tidal surface and background in modeling the seabed, including the acquisition of information about the location of submerged rocky bodies and the depth of these bodies may turn out to be natural traps for the trapping of oil in case of leaks, and obtain the relationship between types of bed and the hydrodynamic conditions present in the region. In this context, for this study were collected bathymetric data (depth) and physical oceanographic (height of water column, water temperature, intensity and direction of currents, waves and turbidity), meteorological (rainfall, air temperature, humidity, winds and barometric pressure) of the access channel to the Port of Cabedelo / PB and its basin evolution (where the cruise ships dock), and includes tools of remote sensing (Landsat 7 ETM +, 2001), so that images and the results are integrated into Geographic Information Systems and used in the elaboration of measures aimed at environmental protection areas under the influence of this scale facilities, serving as a grant to prepare a contingency plan in case of oil spills in the region. The main findings highlight the techniques of using hydroacoustic data acquisition together bathymetric surveys of high and low frequency. From there, five were prepared in bathymetric pattern of Directorate of Hydrography and Navigation - DHN, with the depth in meters, on a scale of 1:2500 (Channel and Basin Evolution of Access to Port of Cabedelo), where there is a large extent possible beachrocks that hinder the movement of vessels in the port area, which can cause collisions, running aground and leaking oil. From the scatter diagram of the vectors of currents, it can be seen as the tidal stream and undergoes a channeling effect caused by the bidirectional effect of the tide (ebb and flood) in the basin of the Port of Cabedelo evolution in NW-direction SE and the highest speed of the currents occurs at low tide. The characterization weather for the period from 28/02 to 04/07/2010 values was within the expected average for the region of study. The multidisciplinary integration of products (digital maps and remote sensing images), proved to be efficient for the characterization of underwater geomorphological study area, reaching the aim to discriminate and enhance submerged structures, previously not visible in the images / O Estado da Para?ba ? um dos estados mais din?micos do Brasil, estrategicamente localizado na regi?o nordeste, se destaca pelo excelente potencial para integra??o dos diversos modais de transporte formado com os Estados do Rio Grande do Norte, Pernambuco e Alagoas e por abrigar o Porto de Cabedelo. A din?mica que ocorre com a atividade portu?ria provoca mudan?as no espa?o onde ele ? instalado. E os elementos que comp?em esse espa?o passam ent?o a sofrer sempre mais influ?ncias diretas ou indiretas ? medida que o fluxo no porto ? ampliado. Logo, essa regi?o tornou-se pass?vel ao derramamento acidental de ?leo, por apresentar um intenso tr?fego de navios de diversos portes que podem encalhar ou colidir ocasionando eventos acidentais com ?leo. O estudo das composi??es geomorfol?gicas e sedimentol?gicas do fundo oce?nico tornam-se importantes ? medida que se conhece mais a respeito de rela??es entre estes par?metros e a fauna associada, sendo poss?vel identificar seus habitats preferenciais. O banco de dados de fundo, acusticamente coletados ao longo da ?rea do estudo proposto, constitui um grande acervo de informa??es, que foram devidamente analisadas, catalogadas e disponibilizadas. Tais informa??es podem servir como uma importante ferramenta, proporcionando um levantamento geomorfol?gico da ?rea estudada, e vir a subsidiar, de forma ?gil, futuras tomadas de decis?o. Tendo como ?rea de estudo Porto de Cabedelo, Para?ba - Brasil, esta pesquisa objetivou avaliar a influ?ncia das correntes de mar?s superficiais e de fundo na modelagem do leito marinho, incluindo a aquisi??o de informa??es sobre a localiza??o de corpos rochosos submersos e a profundidade desses corpos que podem vir a se tornar armadilhas naturais para o aprisionamento de ?leo em casos de vazamentos, al?m de obter a rela??o entre tipos de leito e as condi??es hidrodin?micas atuais na regi?o. Nesse contexto, para este trabalho, foram coletados dados batim?tricos (profundidade) e f?sico-oceanogr?ficos (altura de coluna d ?gua, temperatura da ?gua, intensidade e dire??o das correntes, ondas e turbidez), meteorol?gicos (precipita??o pluviom?trica, temperatura do ar, umidade do ar, ventos e press?o barom?trica) do canal de acesso ao Porto de Cabedelo/PB e sua bacia de evolu??o (local onde os navios atracam), incluindo ainda ferramentas do Sensoriamento Remoto (imagens Landsat 7 ETM+, 2001), para que as imagens e os resultados obtidos sejam integrados em Sistemas de Informa??o Geogr?fica e utilizados na elabora??o de medidas que visem ? prote??o ambiental de ?reas sob influ?ncia de instala??es desse porte, servindo como subs?dio para elabora??o de um plano de conting?ncia em casos de derrames de ?leo na regi?o. Como principais resultados destacam-se as t?cnicas de aquisi??o de dados hidroac?sticos utilizando em conjunto levantamentos batim?tricos de alta e baixa frequ?ncia. A partir disso, foram elaboradas cinco cartas batim?tricas no padr?o da Diretoria de Hidrografia e Navega??o - DHN, apresentando a profundidade em metros, na escala de 1:2.500 (Bacia de Evolu??o e Canal de Acesso ao Porto de Cabedelo), onde observa-se em grande extens?o poss?veis arenitos praiais que dificultam a movimenta??o das embarca??es na ?rea do porto, podendo provocar colis?es, encalhe e vazamentos de ?leo. A partir do digrama de dispers?o dos vetores de correntes, pode-se observar como a corrente de mar? sofre uma canaliza??o e com sentido bidirecional provocado pelo efeito da mar? (vazante e enchente) na bacia de evolu??o do Porto de Cabedelo, no sentido NW-SE e que a maior velocidade das correntes ocorre na baixa-mar. A caracteriza??o meteorol?gica referente ao per?odo de 28/02 a 04/07/2010 apresentou valores dentro das m?dias esperadas para a regi?o de estudo. A integra??o de produtos multidados (mapas digitais e imagens de sensores remotos), mostrou-se eficiente para a caracteriza??o geomorfol?gica submersa da ?rea estudada, alcan?ando o intuito de discriminar e real?ar estruturas submersas, antes n?o percept?veis nas imagens

Page generated in 0.0469 seconds