Detailed surveys of several segments of the Peru Trench show that the region between 6° to 10⁰ S is an area of recent deformation. Seismic reflection records across the axis of the trench show faulting, uplift, and tilting of the sedimentary fill and the acoustic basement. Uplift of the acoustic basement beneath the trench is greatest at 7°40'S and 9°20'S where ridges are elevated above the trench floor. Turbidites occur on top of the ridge at 9°20'S and seaward of the ridge in a basin which is elevated 300 m above the main trench floor. Based upon a hemipelagic sedimentation rate of 1.7 cm/1000 yr, the age of uplift of the ridge is dated at less than 10,000 yrs. B.P. Similarly, the age of uplift of the elevated basin seaward of the ridge is dated at less than 34,000 yrs. B.P. near the ridge and at less than 53,000 yrs. B.P. at the seaward edge of the basin. The trench shoals and turns eastward as one proceeds from south to north along the axis. It divides naturally into three segments separated by the axial ridges at 7°40'S and 9°20'S. The southern segment trends N31W and has an axial depth of 6300 m; the middle segment trends N24W at 6200 m; and the northern segment trends N11W at 5800 m. The upper continental slope is characterized by submarine canyons which funnel sediments into the trench axis. The lower slope is characterized by benches. These benches may define old imbricate thrust sheets. Ridges in the axis are thought to be new imbricate thrust sheets which are forming at the boundaries between segments of the subducted lithosphere. An apparent fracture zone trending N45E enters the area from the southwest. Two turbidite basins (B1 and B2) trending N9E occur northeast of this fracture zone. Turbidite deposition ended in these basins 5100 yrs. ago. The basins intersect the trench axis just north of the ridge at 7°40'S and are presently 700 m above the trench axis. This relative difference in depth is attributed to a combination of subsidence of the trench and uplift of the oceanic plate upon initiation of thrust faulting which presumably occurred 5100 yrs. B.P. There is still insufficient data to determine the exact origin of these basins. From the regional structure, it appears that the lower continental slope of South America is underthrusting the upper continental slope along old imbricate thrust faults beneath the Peruvian continental slope. This overthrusting has caused uplift and accretion of the continental slope and shelf edge and subsidence and sediment infilling of the area between the shelf edge and the coastline. The author suggests that the seismic gap (present lack of large magnitude shallow earthquakes in this area) may be in part due to the highly fractured and deformed nature of the subducted Nazca Plate. Finally, using variable motion along old imbricate thrust faults, the imbricate thrust model provides mechanisms for reorientation of the trench and for episodic subduction of the oceanic plate beneath the trench axis. / Graduation date: 1974

Thesis (M.S.)--Joint Program in Oceanography/ Applied Ocean Science and Engineering, Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, 2003. / Includes bibliographical references (p. 768-69).

This study explores the physical features in the urban setting that give rise to inequitable outcomes for people with disabilities (PWDs), in particular, those with mobility impairments. The objective is to identify the dynamic elements of local active mobility networks that act as barriers to PWDs. A review of the principles and metrics of contemporary urban and transportation planning theory and practice is undertaken. This is contrasted against studies that define the heterogeneous needs and preferences of the disabled population. From this, a new framework is introduced - social topography. This model visualizes the community as a network of opportunities embedded into the physical and socio-economic fabric of the community. It is used as a tool for assessing active mobility networks of three neighbourhoods centered on transportation hubs in southern British Columbia, Canada. The audits reveal that accessibility is a complex and dynamic concept that should inform urban and transportation planning policy and practice. The nuances of absolute and relative access challenges are revealed when the social topography framework is applied. In order to reduce the inequitable outcomes that exist, urban and transportation planning will need to reconsider the underlying principles implicitly and explicitly employed as well as the measures and tools deployed. In the end, individuals and communities will benefit from this more inclusive urban planning paradigm.

Thesis (Master of Science)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution,2008. / Bibliography: p. 62-63.

Thesis--Massachusetts Institute of Technology (Ph. D. Geology). / Photocopy of typescript, Microfilm -- 1 reel ; 35 mm.

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Made available in DSpace on 2014-06-11T19:30:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-09-08Bitstream added on 2014-06-13T18:40:09Z : No. of bitstreams: 1 dalbeto_ac_me_botib.pdf: 512250 bytes, checksum: 74cf55a9258484f70078078b132aeb9a (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este estudo teve como objetivo analisar as comunidades de aves em duas variáveis topográficas de 480m Porção Norte (PN) e 520m Porção Sul (PS) na Estação Ecológicas dos Caetetus, verificando assim, suas relações ecológicas quanto a composição de espécies, abundância, estrutura trófica e estratificação da avifauna, bem como testar se há variações na detecção de espécies e indivíduos em períodos diferentes em dois períodos do dia (manhã e tarde) e do ano, sendo o período chuvoso (dezembro de 2007 a abril 2008) e seco (maio a setembro de 2008). O estudo ocorreu entre os meses de dezembro de 2007 a janeiro de 2008, utilizou-se o método de Ponto de Escuta. O levantamento quantitativo registrou 125 espécies para PN e 156 espécies para PS. O Índice Pontual de abundância variou de 0,008 (1 contato) a 0,87 (210 contatos) na PN e de 0,004 (1 contato) a 0,91 (219 contatos) na PS. A diversidade para PN foi de = 3,76 e para PS H’ = 2,68. A comunidade de aves mostrou o mesmo padrão encontrado em outros fragmentos florestais de mata estacional semidecidual. Os insetívoros foram a categoria mais representativa, sendo a família Tyrannidae a que mais se destacou nas duas porções. As diferenças encontradas entre as duas porções foram resultantes das características da vegetação que garantiram boa parte das espécies exclusivas na PS, o que indica a forte influência da vegetação nas aves. O estudo da influencia do dia, mostrou os dados apóiam a idéia de maior atividade das aves se dá durante a manhã, sendo este período responsável pelo registro significativo de mais espécies e indivíduos. Já a analise da influência do regime de chuvas na EECa não influenciou a distribuição das aves / This study it had as objective to analyze the communities of birds in two topographical variable of 480m Porção Norte (PN) and 520m Porção Sul (PS) in the ecological Station Ecological of the Caetetus, thus verifying, its relations how much the species composition, abundance, structures of guildas and stratification of avifauna, as well as testing if it has variations in the species detention and individuals in different periods in two periods of the day (morning and late) and of the year, being the rainy period (December of 2007 April 2008) and dry (May the September of 2008). The study the January of 2008 occurred enters the months of December of 2007, used the method of Point of Listening. The quantitative survey registered 125 species for PN and 156 species for PS. The Prompt Index of abundance varied of 0,008 (1 contact) the 0,87 (210 contacts) in the PN and of 0,004 (1 contact) the 0.91 (219 contacts) in the PS. The diversity for PN was of = 3,76 and for PS H' = 2,68. The community of birds the same showed standard found in other forest fragmentos of semidecidual estacional bush. The insetívoros had been the category most representative, being the Tyrannidae family the one that more was distinguished in the two portions. The differences found between the two portions had been resultant of the characteristics of the vegetation that had guaranteed good part of the exclusive species in the PS, what it indicates the strong influence of the vegetation in the birds. The study of it influences of the day, it showed the data support the idea of bigger activity of the birds if of the one during the morning, being this responsible period for the significant register of more species and individuals. Already it analyzes it of the influence of the rain regimen in the EECa did not influence the distribution of the birds

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