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Rossana Vai Francisco Luzón Ursula Iturrarán-Viveros Francisco J. Sánchez-Sesma 《Journal of Applied Geophysics》2009,67(1):1-8
Some numerical experiments are designed to elucidate geometrical details of fractures by studying scattering of elastic waves. The response in the time domain does not seem to provide much information. In the frequency domain, geometrical features of diffractors stamp a signature on reflected and diffracted wave fields. Results show that radiation patterns in the Mie regime are a promising device to infer some aspects such as shape and connectivity of the fractures. A combination of the direct and the indirect boundary element methods is used to compute numerical results. The numerical method is validated with analytic solutions for canonical problems. 相似文献
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Michel Villeneuve Jean-Jacques Cornée Agus Harsolumakso Rossana Martini et Louisette Zaninetti 《Eclogae Geologicae Helvetiae》2005,98(2):297-310
Resume. De nombreuses échelles stratigraphiques de l’?le de Timor ont vu le jour car les corrélations stratigraphiques étaient rendues
difficiles par la complexité tectonique de l’?le et par la variété des faciès. Dès les premiers travaux, plusieurs séries
ont été distinguées, regroupées en trois unités litho-structurales principales: unité allochtone, sub-autochtone et autochtone.
Les données stratigraphiques et géodynamiques récentes montrent que l’?le de Timor est en fait constituée par six unités litho-structurales,
chacune témoignant d’un épisode majeur de l’histoire géologique de l’Ile. Cette histoire consiste d’abord à la séparation,
au Jurassique, d’un bloc issu du continent de Gondwana (unité para-allochtone) qui est entré en collision avec l’arc volcanique
asiatique à l’Oligo-Miocène (unités allochtone et sub-allochtone). Cet ensemble a ensuite été séparé de l’Asie lors de l’ouverture
de la mer de Banda sud, au Miocène supérieur (unité sub-autochtone) pour finalement entrer en collision avec la marge nord
australienne au cours du Pliocène moyen (plateforme australienne et groupe de Kolbano). Timor est depuis incorporée à la marge
nord australienne (unité autochtone).
Ce travail présente les différentes échelles stratigraphiques de chaque nouvelle unité, des propositions de corrélations et
une comparaison avec les ?les voisines de Sumba et de Sulawesi pour aboutir à une proposition d’évolution géodynamique.
Manuscrit re?u le 13 février 2004 Révision acceptée le 14 février 2005 相似文献
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Triassic stratigraphy,facies and evolution of the Arabian shelf in the northern United Arab Emirates
Florian Maurer Roberto Rettori Rossana Martini 《International Journal of Earth Sciences》2008,97(4):765-784
This study provides a reconstruction of the Late Permian and Triassic depositional history of the Arabian shelf in the northern
United Arab Emirates based on facies analysis and foraminiferal biostratigraphy. The presented data show that sedimentation
occurred in three major sequences. From the Late Permian to Olenekian carbonates and evaporites were deposited in restricted
lagoons and tidal flats. After a hiatus, sedimentation resumed and continued until the Late Ladinian/Carnian, leading to the
deposition of a carbonate platform dominated by peritidal dolostones. A period of shelf exposure and erosion, spanning from
the Carnian to Norian, was followed by the third major sequence with sedimentation into the Early Jurassic. During this third
depositional sequence sedimentation changed from pure carbonate into mixed carbonate–siliciclastic deposits. This transition
reflects the global regression of the sea in the Late Triassic (Triasina hantkeni Zone) and the increased erosion of large parts of the Arabian hinterland. A comparison of the evolution of the Arabian shelf
in the study area with chronostratigraphic reference schemes for the Arabian Plate reveals remarkable differences in the distribution
of Middle and Upper Triassic sequences. These are most likely the result of poor biostratigraphic control on previously studied
formations in the region. 相似文献
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Michel Villeneuve Jean-Jacques Corne Rossana Martini Louisette Zaninetti 《Comptes Rendus Geoscience》2004,336(16):1511-1520
Similar lithological and tectonic features indicate that Timor and Sulawesi islands were part of the same continental block. Timor was in the southern part of Sulawesi, then separated during Late Miocene time during the opening of the South Banda Sea basin. At this time Timor evolved as a part of an Upper Miocene volcanic arc that collided the Australian plate at the end of the Lower Pliocene (3.5 Ma). To cite this article: M. Villeneuve et al., C. R. Geoscience 336 (2004). 相似文献
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Diatoms consumed by Rio Grande silvery minnows (Hybognathus amarus) collected 104 years apart were used to deduce ecological requirements of this endangered species and to infer a possible
cause of its decline based on environmental conditions in the Rio Grande. In 1874, foraged diatoms were largely motile, silt
tolerant generalist and epipelic species (e.g. Navicula capitatoradiata, Navicula cryptotenella, Nitzschia
palea, Sellaphora pupula) somewhat tolerant to pollution and indicative of eutrophic conditions, low dissolved oxygen, and high biological oxygen
demand (BOD). In contrast, diatoms foraged in 1978 were mainly nonmotile epipsammic species (Fragilariaceae) sensitive to
pollution and characteristic of low nutrient, oligotrophic conditions with high dissolved oxygen and low BOD. The large-scale
difference in composition of the foraged diatom assemblages is consistent with a decline in nutrients and a shift in trophic
state commonly associated with river regulation by dams. The results suggest that facilitating allochthonous input of detritus
and nutrients into the Rio Grande ecosystem to meet foraging requirements for algivorous and detritivorous fish species such
as H. amarus would be a good river restoration strategy. 相似文献
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A novel generalized probabilistic formulation is proposed to assess seismicity using earthquake catalogues with uncertain and incomplete data. The seismicity, described by the complete exceedance rate of magnitudes, is estimated starting from a consistent incomplete exceedance rate which is rationally linked to the catalogue data. Complete and incomplete exceedance rates are represented by similar functional forms and they are related by a completeness function, which expresses the probability that an event is included in a data set. Completeness is considered uncertain and it is defined by a suitable, continuous, analytical, magnitude dependent function. The importance of this work lies on its applicability because it can be useful in seismic zones where information about seismic activity is scarce or simply when the catalogue is incomplete in a range of magnitudes that can have a significant influence on the seismic hazard analysis and on the resulting seismic risk assessment. Moreover, it can also be applied in the common case when the catalogue is considered complete above a given magnitude threshold. Numerical examples are presented to illustrate the influence of catalogue incompleteness on the complete exceedance rate estimations. In companion papers, attention is focused on the estimation of completeness probabilities of available catalogues and on parameter estimation of the exceedance rate functions. 相似文献
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Hongbo Li Yu Liu Kuan Vai Tam Mingyu Zhao Xuefei Zhang 《Astrophysics and Space Science》2018,363(6):118
The material of solar prominences is often observed in a state of flowing. These mass flows (MF) are important and useful for us to understand the internal structure and dynamics of prominences. In this paper, we present a high resolution H\(\alpha \) observation of MFs within a quiescent solar prominence. From the observation, we find that the plasma primarily has a circular motion and a downward motion separately in the middle section and legs of the prominence, which creates a piecewise mass flow along the observed prominence. Moreover, the observation also shows a clear displacement of MF’s velocity peaks in the middle section of the prominence. All of these provide us with a detailed record of MFs within a solar prominence and show a new approach to detecting the physical properties of prominence. 相似文献