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Mathematical Geosciences - When originally developed, the Koval theory was meant to interpret the core-scale production of oil by a miscible displacement by solvent injection. An essential... 相似文献
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Juan Argüelles Ricardo Tafur Anatolio Taipe Piero Villegas Friedeman Keyl Noel Dominguez Martín Salazar 《Progress in Oceanography》2008,79(2-4):308
Changes in population structure of the jumbo flying squid Dosidicus gigas in Peruvian waters were studied based on size-at-maturity from 1989 to 2004. From 1989 to 1999, mature squid belonging to the medium-sized group prevailed, but from 2001 on, mature squids were larger. This change is not related to the changes in sea surface temperature and we hypothesized that it was caused by the population increase of mesopelagic fishes as prey. 相似文献
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About 169000 observations of lunar occultations of stars are analysed for systematic corrections to Watts' charts of the marginal zone of the Moon. Corrections to the radius and shape varying with libration are derived. These are in good agreement with previous results. 相似文献
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Carlos J. Archanjo Ginaldo A. C. Campanha Carlos A. Salazar Patrick Launeau 《International Journal of Earth Sciences》2012,101(3):731-745
The Apiaí gabbro-norite is a massive fine-grained Neoproterozoic intrusion emplaced in a core of synformal structure that
deforms low-grade marine metasedimentary rocks of the Ribeira Belt of south-eastern Brazil. The lack of visible magmatic layering
or any internal fabric has been a major limitation in deciding whether the emplacement occurred before or after the regional
folding. To assist in the tectonic interpretations, we combine low-field anisotropy of magnetic susceptibility (AMS) and silicate
shape preferred orientation (SPO) to reveal the internal structure of the mafic intrusion. Magnetic data indicate a mean susceptibility
of about 10−2 SI and a mean anisotropy degree (P) of about 1.08, essentially yielded by titanomagnetite. The magnetic and silicate foliations for P ≥ 1.10 are parallel to each other, while the lineations tend to scatter on the foliation plane, in agreement with the dominant
oblate symmetry of the AMS and SPO ellipsoids. For lower P values, the magnetic and silicate fabrics vary from coaxial to oblique, and for P ≤ 1.05, their shapes and orientations can be quite distinct. The crystal size distribution (CSD) of plagioclase for P > 1.05 is log linear, in agreement with a bulk simple crystallisation history. These results combined show that for a strong
SPO, corresponding to a magnetic anisotropy above 1.10, AMS is a reliable indicator of the magmatic fabric. They indicate
that the Apiaí gabbro-norite consists of sill-like body that was inclined gently to the north by the regional folding. 相似文献
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Wilfried Haeberli Andreas Linsbauer Alejo Cochachin Cesar Salazar Urs H. Fischer 《地球表面变化过程与地形》2016,41(13):1980-1990
Overdeepenings, i.e. closed topographic depressions with adverse slopes in the direction of flow, are characteristic for glacier beds and glacially sculpted landscapes. Quantitative information about their morphological characteristics, however, has so far hardly been available. The present study provides such information by combining the analysis of (a) numerous bed overdeepenings below still existing glaciers of the Swiss Alps and the Himalaya‐Karakoram region modelled with a robust shear stress approximation and (b) detailed bathymetries from recently exposed lakes in the Peruvian Andes. The investigated overdeepenings exist where glacier surface slopes are low (< 5°–10°), occur in bedrock or morainic material and are most commonly a fraction of a kilometre squared in surface area, hundreds of metres long, about half the length in width and tens of metres deep. They form under conditions of low to high basal shear stresses, at cirque, confluence, trunk valley and terminus positions. The most striking phenomenon, however, is the high variability of their geometries: Depths, surface areas, lengths and widths of the overdeepenings vary over orders of magnitude and are only weakly – if at all – interrelated. Inclinations of adverse slopes do not differ significantly from those of forward slopes and are in many cases higher than so far assumed theoretical limits for supercooling of ascending water and corresponding closure of sub‐glacial channels. Such steep adverse slopes are a robust observation and in support of recently developed new concepts concerning the question about where supercooling of sub‐glacial water and closure of ice channels can or must occur. However, the question of when and under what climatic, topographic and ice conditions the overdeepenings had formed remains unanswered. This open question constitutes a key problem concerning the interpretation of observed overdeepenings, the understanding of the involved glacio‐hydraulic processes and the possibility of realistic predictive modelling of overdeepening formation. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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The republic of El Salvador in Central America is an area of high seismic hazard where at least twelve destructive earthquakes have occurred this century alone. The principal sources of seismic hazard are earthquakes associated with the subduction of the Cocos plate in the Middle America Trench and upper-crustal earthquakes in the chain of Quaternary volcanoes that runs across the country parallel to the subduction trench. Hazard assessments for Central America have suggested almost uniform distribution of hazard throughout El Salvador. Seismic zonations for three successive building codes in El Salvador simply divide the country into two regions, with the higher hazard zone containing the volcanoes and the coastal areas. Historical records suggest that the greatest hazard is posed by the upper-crustal earthquakes concentrated on the volcanic centres which, although of smaller magnitude than the subduction events, are generally of shallow focus and coincide with the main population centres. These earthquakes have repeatedly caused intense damage over small areas in the vicinity of some of the main volcanoes. This study focuses on El Salvador to explore the capability of different approaches to hazard assessment to reflect significant variations of seismic hazard within small geographical areas. In the study, three 'zone-free' methods are employed as well as the Cornell–McGuire approach. The results of the assessments are compared and their implications for seismic zoning for construction and insurance purposes are discussed. 相似文献
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F. J. T. Salazar C. F. de Melo E. E. N. Macau O. C. Winter 《Celestial Mechanics and Dynamical Astronomy》2012,114(1-2):201-213
An alternative transfer strategy to send spacecraft to stable orbits around the Lagrangian equilibrium points L4 and L5 based in trajectories derived from the periodic orbits around L1 is presented in this work. The trajectories derived, called Trajectories G, are described and studied in terms of the initial generation requirements and their energy variations relative to the Earth through the passage by the lunar sphere of influence. Missions for insertion of spacecraft in elliptic orbits around L4 and L5 are analysed considering the restricted three-body problem Earth–Moon-particle and the results are discussed starting from the thrust, time of flight and energy variation relative to the Earth. 相似文献