A global survey of stress orientations in subducting slabs as revealed by intermediate-depth earthquakes   总被引：2，自引：0，他引：2  

Po-Fei Chen  Craig R. Bina  Emile A. Okal 《Geophysical Journal International》2004,159(2):721-733

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Introduction     

Emile A. Okal 《Pure and Applied Geophysics》1991,135(2):167-168

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The Structure of the Nazca Ridge and Sala Y Gomez Seamount Chain From the Dispersion of Rayleigh Waves     

Mark T. Woods  Emile A. Okal 《Geophysical Journal International》1994,117(1):205-222

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Theoretical models for Mars and their seismic properties     

Emile A. Okal  Don L. Anderson 《Icarus》1978,33(3):514-528

Theoretical seismic properties of the planet Mars are investigated on the basis of the various models which have been proposed for the internal composition of the planet. The latest interpretation of gravity field data (Reasenberg, 1977), assuming a lower value of the moment of inertia, would require a less dense mantle and a larger core than previous models. If Mars is chondritic in composition, the most reasonable models are an incompletely differentiated H-chondrite or a mixture of H-chondrites and carbonaceous chondrites. Seismic profiles, travel times, and free oscillation periods are computed for various models, with the aim of establishing which seismic data is crucial for deciding among the alternatives. A detailed discussion is given of the seismic properties which could—in principle—help answer the following two questions: Is Mars' core liquid or solid? Does Mars have a partially molten asthenosphere in its upper mantle?  相似文献   

De l'influence des conditions météorologiques sur la teneur en germes de l'eau du Léman durant l'année 1948     

Emile Novel 《Aquatic Sciences - Research Across Boundaries》1949,11(3-4):555-562

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Groundwater fluctuations and footslope ferricrete soils in the humid tropical zone of southern Cameroon     

Emile Temgoua  Henri‐Bosko Djeuda Tchapnga  Emile Tanawa  Claire Guenat  Hans‐Rudolf Pfeifer 《水文研究》2005,19(16):3097-3111

This paper discusses the relationship between the differentiation of ferruginous accumulations and the variable water saturation of footslope soil patterns. An analysis of the slope morphology of a typical hill in the forest zone of southern Cameroon and a seasonal survey of the levels of groundwaters, springs and rivers were considered in relation to the petrology of different soil patterns. The study site is a tabular hillock whose slopes present a progressive development from steep to gentle slopes. The variable residence time of water within the soil, creating an alternation of reducing and oxidizing conditions, affects soil chemistry, structure and lateral extension of the soil patterns. The ferruginous soil patterns, being formed on the footslopes, gradually increase in extent with decreasing slope angle and the relative rise of the groundwater level. The steep footslopes, where groundwater has a shorter residence time, show a soft mottled clay pattern, restricted to the bottom part of the slope. The moderate footslopes exhibit a deep permanent and a temporary perched groundwater table. The latter, with its regular capillary fringe, contributes to more reducing conditions within isolated domains in the soil patterns, and thus to the alternation with oxidizing conditions, generating a continuous hard soil pattern (massive carapace). The more gently dipping footslopes exhibit groundwater levels near the surface and also a significant amplitude of groundwater fluctuation. Iron, previously accumulated in moderate footslope patterns, is reduced, remobilized, and leached. The soil patterns formed develop into a variegated carapace, more extended along the slope, containing less iron, but nevertheless more hardened, due to the important fluctuations of the groundwater table. These patterns are limited to the zone of groundwater fluctuation and deteriorate as the water fluctuation zone recedes. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

A pollen-based record of late glacial–Holocene climatic variability in the southern lake district, Chile     

Lourdes Vargas-Ramirez  Emile Roche  Philippe Gerrienne  Henry Hooghiemstra 《Journal of Paleolimnology》2008,39(2):197-217

A pollen record from Puyehue area (40°S; 72°W) in the southern Lake District, Chile, indicates that prior to 13,410 ¹⁴C yr BP (ca. 16,500–15,200 cal yr BP), cold resistant and hygrophilous vegetation, particularly Nothofagus forest and myricaceous vegetation, covered the area. From ca. 15,000 cal yr BP onward, the forest became increasingly dense. Between 10,010 and 7450 ¹⁴C yr BP (ca. 11,000–8000 cal yr BP), the expansion of Nothofagus obliqua and the spread of grasses suggests the climate became warmer and semi-arid. Lowland deciduous forest (Nothofagus obliqua, Aextoxicon punctatum, Laurelia sempervirens) and Valdivian rainforest (Nothofagus dombeyi, Eucryphia cordifolia, Caldcluvia paniculata, Aextoxicon punctatum, Laureliopsis philippiana) were abundant. During the next two thousand years, stable warm climatic conditions prevailed, and the diversity of the vegetation increased. From 5760 to 1040 ¹⁴C yr BP (ca. 6500–900 cal yr BP), the North Patagonian rainforest expanded. The presence of Pilgerodendron/Fitzroya, together with Nothofagus forest, suggests that humid conditions prevailed. During the last millennium, human impact intensified and regional vegetation was disturbed, particularly the lowland deciduous forest and Valdivian rainforest. North-Patagonian and subantartic taxa, such as Podocarpus nubigena, Pilgerodendron/Fitzroya, Nothofagus dombeyi type, Austrocedrus chilensis and Drimys winteri, occupied the low and high-altitude parts of the Cordillera. Five hundred years ago, shrub and grasses expanded in the Nothofagus forest, suggesting that forest became more open under cool–cold, and humid climatic conditions. These conditions prevail to the present day. This is the fourth in a series of eight papers published in this special issue dedicated to the 17,900 year multi-proxy lacustrine record of Lago Puyehue, Chilean Lake District. The papers in this special issue were collected by M. De Batist, N. Fagel, M.-F. Loutre and E. Chapron.  相似文献   

Designing Iron‐Amended Biosand Filters for Decentralized Safe Drinking Water Provision     

Chicgoua Noubactep  Emile Temgoua  Mohammad A. Rahman 《洁净——土壤、空气、水》2012,40(8):798-807

There are ongoing efforts to render conventional biosand filters (BSF) more efficient for safe drinking water provision. One promising option is to amend BSF with a reactive layer containing metallic iron (Fe⁰). The present communication presents some conceptual options for efficient Fe⁰‐amended BSF in its fourth generation. It is shown that a second fine‐sand layer should be placed downwards from the Fe⁰‐reactive layer to capture dissolved iron. This second fine‐sand layer could advantageously contain adsorbing materials (e.g. activated carbons, wooden charcoals). An approach for sizing the Fe⁰‐reactive layer is suggested based on 3 kg Fe⁰ per filter. Working with the same Fe⁰ load will ease comparison of results with different materials and the scaling up of household BSF to large scale community slow sand filters (SSF).  相似文献   

Crustal structure in the Society and Tuamotu Islands, French Polynesia     

Jacques Talandier  Emile A. Okal 《Geophysical Journal International》1987,88(3):499-528

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Rayleigh-wave phase velocities in French Polynesia     

Emile A. Okal  Jacques Talandier 《Geophysical Journal International》1980,63(3):719-733

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Rayleigh-wave phase velocities are investigated in the period range 17–100 s by the two-station method over several paths covering most of French Polynesia. Our results confirm the validity of theoretical models obtained through regionalization of data pertaining to longer paths. They also exhibit a 2–3.5 per cent anisotropy, with the axis of maximum velocity oriented in the direction of spreading of the plate. Part of this anisotropy is, however, due to the presence of the Tuamotu archipelago; when this is removed, the remaining anisotropy (about 1.5 per cent) correlates with the present direction of spreading, indicating that a relaxation of the anisotropy has taken place since the East Pacific ridge jump. Finally, the presence of the Tuamotu Islands explains anomalous waveshapes for surface waves travelling in their vicinity, due to multipathing through their faster structure.  相似文献