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Simplified models for cross-section stress demands on C-section purlins in uplift

VIEIRA JR., L. C. M.; MALITE, M.; SCHAFER, B. W.
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.01%
The objective of this paper is to provide and verify simplified models that predict the longitudinal stresses that develop in C-section purlins in uplift. The paper begins with the simple case of flexural stress: where the force has to be applied at the shear center, or the section braced in both flanges. Restrictions on load application point and restraint of the flanges are removed until arriving at the more complex problem of bending when movement of the tension flange alone is restricted, as commonly found in purlin-sheeting systems. Winter`s model for predicting the longitudinal stresses developed due to direct torsion is reviewed, verified, and then extended to cover the case of a bending member with tension flange restraint. The developed longitudinal stresses from flexure and restrained torsion are used to assess the elastic stability behavior of typical purlin-sheeting systems. Finally, strength predictions of typical C-section purlins are provided for existing AISI methods and a newly proposed extension to the direct strength method that employs the predicted longitudinal stress distributions within the strength prediction. (C) 2009 Elsevier Ltd. All rights reserved.; USIMINAS; CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico) (Brazil)

Modelo teórico para controle da capacidade de carga à tração de estacas metálicas helicoidais em solo arenoso; Theoretical model to control on site the uplift capacity of helical screw piles embedded in sandy soil

Tsuha, Cristina de Hollanda Cavalcanti
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/11/2007 PT
Relevância na Pesquisa
37.45%
O monitoramento em campo de fundações em estacas metálicas helicoidais é baseado em correlações empíricas entre a capacidade de carga à tração e o torque medido durante a instalação. Nesta pesquisa é proposto um modelo teórico da relação entre o torque de instalação e a capacidade de carga à tração deste tipo de estaca em areias para ser utilizado como procedimento de controle durante a execução deste tipo de fundação. Para validar esta relação teórica e para avaliar o desempenho desta fundação em solos arenosos, foi realizado um programa experimental dividido em dois grupos: ensaios de campo e ensaios de laboratório. Em campo foram realizadas provas de carga à tração na Escola de Engenharia de São Carlos (EESC) e em Contagem (Minas Gerais). Os ensaios de laboratório foram divididos em três grupos. O primeiro corresponde aos ensaios de modelagem física em centrífuga realizados no Laboratoire Central des Ponts et Chaussées (LCPC) em Nantes, França. O segundo engloba ensaios de cisalhamento direto de interface entre o aço da hélice da estaca e diferentes areias, parte executada no LCPC e parte na EESC. O terceiro grupo refere-se a ensaios de torção de tubos de estacas metálicas helicoidais efetuados na EESC. A partir dos resultados dos ensaios...

Efeito da configuração das hélices na capacidade de carga à tração de estacas metálicas helicoidais em solo tropical; The effect of helices configuration on the uplift capacity of helical piles in a tropical soil

Santos, Thiago da Costa
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 07/03/2013 PT
Relevância na Pesquisa
37.28%
As estacas helicoidais têm sido empregadas em diversos tipos de obras no Brasil e no mundo, principalmente em casos em que a fundação é submetida a carregamentos simultâneos de tração e de compressão ou que necessitam de rápida e facilitada instalação. O maior uso nacional é em fundações de torres de linhas de transmissão de energia, no entanto, são escassos os estudos do comportamento deste tipo de estaca em solos tropicais brasileiros. Considerando-se o crescimento do uso de estacas helicoidais no Brasil, e a necessidade de um melhor entendimento do comportamento deste tipo de fundação em nossos solos, o presente trabalho foi realizado para verificar a influência do arranjo das hélices, tanto do diâmetro quanto da quantidade, na capacidade de carga à tração das estacas helicoidais multi-hélices, instaladas em solo tropical da região de São Carlos, na cidade de Itirapina próxima a lagoa do Broa. A campanha de investigações geotécnicas foi composta por sondagens de simples reconhecimento (SPT) e ensaios de cone (CPT). Foram ensaiadas nove estacas, com diferentes configurações de diâmetro e de número de hélices, instaladas com a ponta em mesma profundidade, mesmo espaçamento entre hélices (igual a três vezes o maior diâmetro) e mesmo diâmetro de haste. Nesta investigação foram medidos os torques de instalação...

Estimativa da capacidade de carga à tração de estacas helicoidais com base no ensaio SPT; Semi-empirical estimation of the uplift capacity of helical piles based on SPT results

Silva, Bruno Canoza da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 07/07/2014 PT
Relevância na Pesquisa
37.35%
Na prática brasileira, usualmente a previsão da capacidade de carga de fundações por estacas é baseada em métodos semi-empíricos, por meio de correlações diretas da resistência de ponta e por atrito lateral ao longo da estaca com os valores de NSPT. Entretanto, no caso de fundações por estacas helicoidais, ainda utilizam-se métodos teóricos que necessitam de valores de parâmetros geotécnicos obtidos indiretamente a partir de correlações com os valores de NSPT (coesão, peso específico, ângulo de atrito, coeficiente de empuxo). Portanto, nesta dissertação foi desenvolvido um método semi-empírico para estimar a capacidade de carga à tração de fundações por estacas helicoidais profundas por meio de correlações diretas com o valor de NSPT do solo de instalação da estaca. Além disso, são apresentados no presente trabalho valores de fator de torque KT, obtidos por análise estatística, para a verificação da capacidade de carga à tração da estaca usando-se medidas do torque necessário para instalá-la no terreno. Nesta pesquisa dois diferentes modelos para estimativa da capacidade de carga foram desenvolvidos e analisados estatisticamente. O estudo das características das amostras de fundações por estacas helicoidais usadas nesta pesquisa permitiu a subdivisão em grupos (tipo de solo e quantidade de hélices) de modo a se obter modelos mais precisos. Com os resultados deste trabalho...

Estudo do arrancamento de fundações em solos tratados com cimento; The uplift performance of footings embedded in cement stabilized backfill

Ruver, Cesar Alberto
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
37.17%
Engenheiros geotécnicos, defrontam-se frequentemente com solos de baixa capacidade de suporte. Para viabilizar projetos nestes materiais, pode-se utilizar fundações com grandes dimensões e/ou melhorar a propriedades mecânicas destes solos. Fundações de grandes dimensões podem ser extremamente onerosas e gerar impactos ambientais indesejáveis provocados por grandes movimentações de solo. Em contrapartida, o melhoramento das propriedades mecânicas do solo pode ser obtido por meio de tratamento com agentes cimentantes. Esta técnica tem-se mostrado bastante promissora nas diversas subáreas da geotecnia, como por exemplo, leito e subleito de pavimentação, estabilidade de taludes e terrenos para assentamento de fundações à compressão. A utilização desta técnica em fundações escavadas submetidas à tração ainda é incipiente. Até meados dos anos 1950, os métodos de previsão de desempenho consideravam somente o peso do solo contido em uma superfície ruptura somado ao peso da fundação, como contribuindo na capacidade de carga ao arrancamento. Estudos recentes passaram a incluir uma terceira parcela de resistência devido à resistência ao cisalhamento do solo. A partir de então diversos autores passaram a estudar técnicas de melhoramento e reforços dos reaterros. Num primeiro momento...

Estudo do comportamento a tração axial de diferentes tipos de estacas em solo de diabasio da região de Campinas/SP; Behavior of different piles, conducted in diabasic soil, submited to uplift efforts

João Alexandre Paschoalin Filho
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 15/08/2008 PT
Relevância na Pesquisa
37.17%
Apresenta-se neste trabalho o estudo do comportamento de diferentes tipos de estacas, implantadas em solo de diabásio, quando submetidas a esforços de tração, através da realização de provas de carga estática do tipo lenta. Foram executadas quatro estacas tipo raiz sendo uma de 23m de comprimento e 310 mm de diâmetro e três instrumentadas de 12m de comprimento com 410 mm de diâmetro; três estacas metálicas perfil I tipo W250x32,7, sendo uma com 12m e duas com 18m de comprimento; duas estacas tipo trilho TR37 sendo uma com 18m e outra de 20,5m de comprimento. Foram também estudadas as seguintes estacas já anteriormente instaladas no local em estudo: três estacas escavadas (sem lama bentonítica) de 12m de comprimento e 400 mm de diâmetro, três estacas tipo hélice contínua com 12m de comprimento e 400 mm de diâmetro, uma estaca tipo ômega de 12m de comprimento e 370 mm de diâmetro e uma estaca prémoldada de oncreto com 14m de comprimento e 180 mm de diâmetro. O local de execução das estacas foi o Campo Experimental para Estudos em Mecânica dos Solos e Fundações localizado dentro dos limites da Faculdade de Engenharia Agrícola da Unicamp (Universidade Estadual de Campinas), localizada no município de Campinas...

Dating the Tejo river lower terraces in the Ródão area (Portugal) to assess the role of tectonics and uplift

Cunha, P.,; Martins, A.; Huot, S.; Murray, A.; Raposo, L.,
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.17%
The Tejo river is one of the major drainages in Iberian Peninsula; it is a long-lived system (ca. 3.4 Ma) and provides an archive of long-term landscape development and environmental change controlled by tectonics, climate and eustasy. The most upstream Portuguese reach of the Tejo river, ∼200 km from the Atlantic coast, shows evidence for five fluvial terraces (T1 to T5) with elevations reaching more than 120 m above the modern river bed. A chronological framework for these terraces is established here by integrating geomorphological, stratigraphical and archaeological information with ages from luminescence dating. Optically stimulated luminescence dating of K-feldspar, (involving the correction for anomalous fading of the luminescence signal), indicates that the younger terraces have a probable age range of: T5 — 31 to 40 ka; and T4 — 100 to ∼280 ka. We deduce that the related major fluvial changes are likely to have been as follows: ∼10 m of aggradation from ∼280 to 100 ka (0.06 m/ka); 14 m of incision from 100 to 40 ka (0.23 m/ka); 8 m of aggradation from40 to 31 ka (0.89 m/ka); 16mof incision during the last 31 ka (0.52m/ka). These values indicate that the duration and rate of both aggradation and river downcutting episodeswere variable. There iswidespread evidence for neotectonic activity in this intraplate region. Neither eustatic nor climatic changes during the Quaternary provide clear trends that might explain the observed pattern of valley incision...

QUANTIFICATION OF FLUVIAL INCISION OF DOURO RIVER TRIBUTARIES (NE PORTUGAL) - BASE LEVEL, DIFFERENTIAL UPLIFT AND LITHOLOGICAL CONTROLS ON THE RIVERS LONG PROFILE EVOLUTION

Martins, António; Gomes, António; Cunha, Pedro; Cabral, João
Fonte: Fluvial Archive Group (FLAG) Publicador: Fluvial Archive Group (FLAG)
Tipo: Aula
POR
Relevância na Pesquisa
37.28%
This study analyses the long profiles of the Águeda, Côa, Távora and Paiva rivers, and of other Douro River lower order tributaries. The Águeda and Côa rivers flow encased on the vast planation surface that characterizes the Hesperian Massif morphology (the Iberian Meseta), while the Távora and Paiva rivers flow through higher, uplifted blocks, located west of the Vilariça fault zone (VFZ). These streams flow through a landscape strongly influenced by variations in bedrock lithology (granites and metasediments), fault structures that promoted differential uplift, and significant base-level changes. The longitudinal profiles of the Douro tributaries commonly display concavities separated by knickpoints/knickzones. The most upstream concavity reflects a relict graded profile of probable Piacenzian – Gelasian age, testifying an Atlantic exoreic drainage coeval of a high sea-level. Downstream concavities reflect the on-going transmission of several incision waves, linked to the Pleistocene - present stage of fluvial incision. In downstream concavities, the stream is graded to transient forms of the river profile with respect to the lithology, structure and base level history. They alternate with convexities (knickzones) developed where the incision waves were delayed...

Surface uplift, fluvial incision, and geodynamics of plateau evolution, from the western margin of the Central Andean plateau

Schildgen, Taylor F. (Taylor Frances)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 154 leaves
ENG
Relevância na Pesquisa
27.61%
The Colca-Majes and Cotahuasi-Ocona rivers in southwest Peru that cut through the western margin of the Andean plateau en route to the Pacific Ocean incised canyons over 3 km deep in response to late Cenozoic surface uplift. This latest uplift represents a fundamental shift in the style and magnitude of surface deformation that had been ongoing since at least late Cretaceous time, but only relatively recently created what represents the only major barrier to atmospheric circulation in the Southern Hemisphere. Studying canyon incision history as a proxy for surface uplift offers a promising route to understanding how climate and tectonics have interacted throughout the evolution of the Central Andean plateau. In this thesis, a combination of bedrock low-temperature thermochronology (apatite and zircon (UTh)/He techniques), 40Ar/39Ar dating of valley-filling volcanic flows, and three-dimensional thermal modeling using a modified version of Pecube were applied to investigate the incision history of the rivers. Results suggested between 2.6 and 3.0 km of incision occurred in the deepest reaches of the canyons starting at ca. 10 to 11 Ma and ending between 2.3 and 3.5 Ma. The onset of surface uplift that is likely to have driven incision probably did not precede incision by more than one million years...

Effects of Architectural Features of Air-Permeable Roof Cladding Materials on Wind-Induced Uplift Loading

Li, Ruilong
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Relevância na Pesquisa
37.49%
Widespread damage to roofing materials (such as tiles and shingles) for low-rise buildings, even for weaker hurricanes, has raised concerns regarding design load provisions and construction practices. Currently the building codes used for designing low-rise building roofs are mainly based on testing results from building models which generally do not simulate the architectural features of roofing materials that may significantly influence the wind-induced pressures. Full-scale experimentation was conducted under high winds to investigate the effects of architectural details of high profile roof tiles and asphalt shingles on net pressures that are often responsible for damage to these roofing materials. Effects on the vulnerability of roofing materials were also studied. Different roof models with bare, tiled, and shingled roof decks were tested. Pressures acting on both top and bottom surfaces of the roofing materials were measured to understand their effects on the net uplift loading. The area-averaged peak pressure coefficients obtained from bare, tiled, and shingled roof decks were compared. In addition, a set of wind tunnel tests on a tiled roof deck model were conducted to verify the effects of tiles’ cavity internal pressure. Both the full-scale and the wind tunnel test results showed that underside pressure of a roof tile could either aggravate or alleviate wind uplift on the tile based on its orientation on the roof with respect to the wind angle of attack. For shingles...

Impacts of neogene-recent compressional deformation and uplift on hydrocarbon prospectivity of the passive southern Australian margin

Holford, S.; Hillis, R.; Duddy, I.; Green, P.; Tuitt, A.; Stoker, M.
Fonte: Australian Petroleum Production and Exploration Association Publicador: Australian Petroleum Production and Exploration Association
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
37.35%
The passive southern margin of the Australian continent, which formed following Cretaceous-Palaeogene separation from Antarctica, contains a rich record of Neogene-Recent compressional deformation and uplift. This deformation and uplift is manifested by reversal of displacement along syn-rift extensional faults, folding of mid-late Cenozoic post-rift sediments, and regional unconformities that can be traced for distances of up to 1500 km along the margin. Palaeothermal data from onshore and offshore exploration wells indicate that erosion associated with deformation and uplift locally exceeds 1 km in the eastern Otway Basin. Both neotectonic palaeostress trends inferred from these structures and present-day stress orientations are consistent with NW-SE directed compression controlled to first-order by plate boundary forces. The critical role of the relative timing of trap formation and source rock maturation in controlling hydrocarbon prospectivity in the southern Australian margin is investigated by comparing two structures that formed during Neogene-Recent deformation in the Otway Basin, the Minerva and Nerita anticlines. Whilst the Minerva Anticline hosts a major gas field (558 BCF GIP), the Nerita Anticline was found to be dry. A combination of apatite fission track analysis (AFTA)...

Paleothermal and seismic constraints on late Miocene-Pliocene uplift and deformation in the Torquay sub-basin,southern Australian margin

Holford, S.; Hillis, R.; Duddy, I.; Green, P.; Tassone, D.; Stoker, M.
Fonte: Taylor & Francis Ltd. Publicador: Taylor & Francis Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
37.35%
The passive southern margin of the Australian continent contains a rich record of late Miocene– Pliocene neotectonic deformation and uplift that continues to the present day as witnessed by unusually high levels of seismicity for a so-called ‘stable continental region.’ To date, however, few studies have sought to estimate the magnitude of exhumation triggered by this deformation and uplift. Here we combine apatite fission track analysis (AFTA), apatite (U–Th)/He dating and vitrinite reflectance (VR) data from the Nerita-1 well in the Torquay sub-basin with seismic reflection data from this basin and the adjoining Otway Ranges to constrain the magnitude and drivingmechanisms of exhumation in this part of the southern Australian margin. The Cenozoic succession in this basin has been deformed by folding and reverse faulting and contains a major, low-angle mid-Miocene unconformity that can be traced for distances of *1500 km along the margin. Paleothermal data from Nerita-1 show that the sub-mid-Miocene succession has been more deeply buried by *1 km of now missing section, and indicate that exhumation began between 10 and 5 Ma, in excellent agreement with stratigraphic constraints. Our estimates of removed section and higher than previous estimates based on extrapolation of seismic reflectors...

Dynamic response of multi-degree of freedom structure with sliding isolation system and uplift

Vemuru, Venkata Srivishnu Mohan
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
27.52%
In this study the two dimensional dynamic response of a Multi Degree of Freedom (MDOF) sliding isolated structure permitted to uplift is studied. The MDOF superstructure is supported by two sets of sliding bearings situated at both the ends of the base mat. The foundation supporting the sliding bearings is assumed to be flexible and modeled using two sets of viscoelastic spring-dashpot systems attached below the sliding isolation bearings. The nonlinear stick-slip behavior of the friction based sliding isolation system is modeled using a hysteretic Bouc-Wen model. A nonlinear analytical model is formulated which takes into account the linear equations of motion of the superstructure and the base mat with stick-slip behavior of sliding isolators and in addition the following effects: uplift and loss of contact at the sliding bearings, and variation of coefficient of friction with velocity and bearing pressure. For comparison purposes fixed base structure with uplift is also modeled. The analytical model is solved using a two-step solution methodology and Pseudo-force method is employed for calculating the nonlinear forces acting on the structure at the interface of sliding isolation system in both the horizontal (stick-slip) direction as well as the vertical (uplift-contact direction). The analytical model developed is validated using experimental results of a 1:4 scaled model. Parametric study is performed with the analytical model (at full scale) by varying the periods of the superstructure...

Late Cretaceous uplift in the Malargüe fold-and-thrust belt (35°S), Southern Central Andes of Argentina and Chile

Mescua, Jose Francisco; Giambiagi, Laura Beatriz; Ramos, Victor Alberto
Fonte: Servicio Nacional Geologia Minerva Publicador: Servicio Nacional Geologia Minerva
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
Relevância na Pesquisa
37.17%
The Cordillera de los Andes is the typical example of a subduction-related orogen. Its present topography is the result of post-Miocene uplift, however, Andean compressional deformation and uplift started in the Late Cretaceous, as increasingly recognized in different sectors of the mountain belt. We present evidences of a Late Cretaceous event of compressional deformation in the southern Central Andes (35ºS), reflected in syn-orogenic foreland basin deposits assigned to the Neuquén Group in Argentina and the Brownish-Red Clastic Unit in Chile. Comparison of the facies of these units allows us to recognize a sector proximal to the Late Cretaceous orogenic front, a distal sector with sediment provenance from the forebulge and a western sector where the sediments where deposited within the Late Cretaceous mountain belt. On this basis, we assign the orogenic front to an inverted Jurassic normal fault, the Río del Cobre fault, and reconstruct the structure of the easternmost Late Cretaceous Andes at this latitude. The change in the location of the orogenic front north and south of 35ºS allows us to recognize a long-lived change in behavior in Andean evolution in this sector, which correlates with a change in the shape and the deposits of Mesozoic Neuquén basin.; Levantamiento Cretácico Tardío en la faja plegada y corrida de Malargüe (35oS)...

Uplift rates defined by U-series and 14 C ages of serpulid-encrusted speleothems from submerged caves near Siracusa, Sicily (Italy)

Dutton, Andrea; Scicchitano, Giovanni; Monaco, Carmelo; Desmarchelier, Jolyon; Antonioli, Fabrizio; Lambeck, Kurt; Esat, Tezer; Fifield, L Keith; McCulloch, Malcolm; Mortimer, Graham
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.17%
We have established a plausible rate of uplift near Siracusa in southeastern Sicily (Italy) over the last glacial-interglacial cycle using U-series ages of submerged speleothem calcite and 14C ages of calcite serpulid layers that encrust the speleothems d

Evidence for long-term uplift on the Canary Islands from emergent Mio–Pliocene littoral deposits

Meco, Joaquín; Scaillet, Stéphane; Guillou, Hervé; Lomoschitz, Alejandro; Carracedo, Juan Carlos; Ballester, Javier; Betancort, Juan Francisco; Cilleros, Antonio
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 2373 bytes; 2316077 bytes; text/plain; application/pdf
ENG
Relevância na Pesquisa
37.17%
13 pages, 9 figures, 1 table.-- Printed version published Jun 2007.; Several islands in the Canarian archipelago show marine deposits with identical fossil faunas, which are generally assigned to different glacioeustatic marine episodes: mainly Pleistocene episodes in Lanzarote and Fuerteventura, and Mio–Pliocene ones in Gran Canaria.; Three fossil species (Saccostrea chili, Nerita emiliana and Strombus coronatus) characterize all the marine deposits from southern Lanzarote, to the west and south of Fuerteventura and northeast of Gran Canaria. Three other species (Ancilla glandiformis, Rothpletzia rudista and Siderastraea miocenica) confirm the chronostratigraphic attribution of these deposits. Other more occasional fossils (as Chlamys latissima, Isognomon soldanii and Clypeaster aegyptiacus) fit an upper Miocene and lower Pliocene age. This agrees with new K/Ar ages obtained from pillow lavas emplaced into the marine deposits (ca. 4.1 Ma in Gran Canaria, ca. 4.8 Ma in Fuerteventura) and from underlying (ca. 9.3 Ma in Gran Canaria) or overlying (ca. 9.8 Ma in Lanzarote) lava flows.; The marine deposits are eroded but large continuous segments are preserved sloping gently towards the coast. Variations in the highest and the lowest elevations of the deposits apsl (above present sea level) indicate post-depositional uplift movements. Glacioeustatic causes are unlikely to be responsible for these variations on the basis of the coastal location of the deposits and their equatorial fauna characteristic of Mio–Pliocene corals. Differential uplift of the deposits across the archipelago is argued to result from the progressive seaward tilting of the islands along the insular volcanic trail marking the westward migration of hot spot head since 20 Ma. Successive westward accretion of younger volcanic edifices resulted in increasing lithostatic load of the crust with progressive (diachronous) tilting of the older edifices and their palaeo-shorelines marked by past coastal deposits.

Elongated domes in extended orogens: A mode of mountain uplift in the Betics (southeast Spain)

Martínez-Martínez, José Miguel; Soto, J. I.; Balanyá, Juan Carlos
Fonte: Geological Society of America Publicador: Geological Society of America
Tipo: Artículo Formato: 13824 bytes; application/vnd.ms-excel
ENG
Relevância na Pesquisa
37.01%
The Sierra Nevada elongated dome in the Betic hinterland (westernmost Mediterranean region) formed by polymetamorphic, non-melted rocks involving crustal thickening and subsequent exhumation via extensional denudation including both normal faulting and vertical ductile thinning. Core rocks record a clockwise P-T-t path with segments of quasi-isothermal decompression that do not cross the melting solidi. Doming was caused by the interference of two orthogonal sets of Miocene-Pliocene, large-scale open folds (trending roughly E-W and N-S) that warp both WSW-directed extensional detachments and the footwall regional foliation. N-S folds were generated by a rolling hinge mechanism while E-W folds formed due to shortening perpendicular to the direction of extension. Strike-slip faults striking subparallel to the direction of extension laterally bound the domes, adjoining highly extended domains to less extended blocks. Using a three-dimensional model of the crustal structure of the Sierra Nevada elongated dome constrained by surface geological data, the relationships with present-day topography, and the deep crustal structure, this paper explores the role of crustal flow in the origin and evolution of the dome. Collectively, the crustal structure...

Late Holocene uplift of Rhodes, Greece: evidence for a large tsunamigenic earthquake and the implications for the tectonics of the eastern Hellenic Trench System

Howell, Andy; Jackson, James; England, Philip; Higham, Tom; Synolakis, Costas
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Article; published version
EN
Relevância na Pesquisa
37.28%
This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/gji/ggv307; Several large earthquakes in the Hellenic subduction zone have been documented in historical records from around the eastern Mediterranean, but the relative seismic quiescence of the region over the period of instrumental observation means that the exact locations of these earthquakes and their tectonic significance are not known. We present AMS radiocarbon dates from uplifted late Holocene palaeoshorelines from the island of Rhodes, showing that uplift is most consistent with a single large (MW ? 7:7) reverse-faulting earthquake between about 2000 BC and 200 BC. Analysis of the uplift treating the earthquake as a dislocation in an elastic half space shows a predominantly a reverse-faulting event with a slip vector oblique to the direction of convergence between Rhodes and Nubia. We suggest that the fault responsible for the uplift dips at an angle of 30-60? above the more gently-dipping oblique subduction interface. The highly oblique convergence across the eastern Hellenic plate boundary zone appears to be partitioned into reverse slip on faults that strike parallel to the boundary and strike-parallel or oblique slip on the subduction interface. Hydrodynamical simulation of tsunami propagation from a range of tectonically plausible sources suggests that earthquakes on the fault uplifting Rhodes represent a significant tsunami hazard for Rhodes and SW Turkey...

Exploring Links between Climate and Orogeny by Estimating Uplift with a Physical-Statistical Model

Lowman, Lauren Elizabeth Lee
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Tese de Doutorado
Publicado em //2013
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37.41%

The Andes Mountains provide a unique setting to study the interplay between climate and geomorphology. The mechanism proposed to describe the evolution of Andean topography is a feedback loop where precipitation erodes the surface, causing the earth's crust to thin and, through buoyancy, uplift the surface. The uplifted surface acts as a barrier which in turn increases precipitation and reinforces the feedback. Demonstrating this feedback is difficult due to the long temporal scales involved. To overcome this challenge, we consider current topographic constraints and climate regimes as a means to evaluate geomorphologic behavior. Initial data analysis leads to the identification of qualitative similarities in the distributions of outlets and precipitation events by elevation, which suggest a link between climatic and fluvial erosion and a strong interaction between orography and precipitation. To explore impacts of this link on regional geomorphology, we estimate uplift rates under a Bayesian hierarchical modeling framework based on the stream power erosion law (SPEL). We specify model parameters using slope and area data generated from a high-resolution, digital elevation map and mean annual precipitation (MAP) derived from 14 years of TRMM 3B42 v.7 precipitation rainfall rates...

Post-Palaeozoic uplift history of southeastern Australia revisited: results from a process-based model of landscape evolution

Van der Beek, Pieter A; Braun, Jean; Lambeck, Kurt
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
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Developments over the last decade in the debate concerning the geomorphic evolution of the southeastern Australian highlands are reviewed, taking as a starting point the model of passive denudation and isostatic rebound of a Palaeozoic mountain belt presented by Lambeck and Stephenson (1986). This model has been popular in the geomorphological community because it provides a quantitative framework to explain the very low rates of landscape evolution inferred from most geomorphological studies. The model has, however, also been criticised for its treatment of erosion as being linearly dependent on elevation, as well as for its predictions of regional uplift and denudation patterns that are not in accord with inferences from fission-track thermochronological data. First results of a new physical process-based model for large-scale, long-term landscape evolution in the southeastern highlands are presented. These show that the denudation history and drainage development of southeastern Australia can be explained to a first order without invoking large-scale mid-Cretaceous or Tertiary uplift events. The model predicts drainage patterns in southeastern Australia to have evolved by rearrangement of an initially northwesterly directed drainage net...