1,720,992 research outputs found
The contribution of Anisotropy of Magnetic Susceptibility (AMS), Anisotropy of P-wave Velocity (APV) and Petrophysic analysis in the strain characterisation at Sheep Mountain Anticline (Wyoming, USA)
No full textRobion, P., Amrouch, K., Callot, J., Lacombe, O., Daniel, J., Bellahsen, N
Dynamics of Subduction and Plate Motion in Laboratory Experiments.
No full text3-D laboratory experiments have been designed to investigate the way slab-bearing plates move during subduction inside the mantle. The boundary conditions are as simple as possible: a viscous plate rests in the center of a large tank filled up by honey and subducts under its negative buoyancy once a small instability at the plate edge is created. Varying thickness, width, viscosity, density of the plate and mantle, three characteristic modes of subduction are observed: a retreating trench mode (Mode I), a retreating trench mode following a transient period of advancing trench (Mode II), and an advancing trench mode (Mode III). These modes are characterized by different partitioning of the amount of subduction into plate and trench motion. Our experiments show that the velocity of subduction can be roughly modeled by the dynamic interaction between acting and resisting forces and that some parameters such as the slab viscosity or thickness have the opposite influence than the one usually suggested in the literature. This result is interpreted as the consequence of the dependence (measured in the experiments) of the slab radius of curvature on the plate viscosity and thickness. However, it is still far from being simple to predict how the trench and plate move. Our results suggest that the complexity of the style of subduction could also be controlled by simple geometrical rules of a plate bending inside a stratified mantle: our planet system is in the crucial range where the length of the slab pulling down the plate is about the double of its radius of curvature
Subduction And Plate Motion In Laboratory. European Geosciences Union.
No full textWe have performed 3-D laboratory experiments to test the influence of factors controlling plate and trench motion of a subducting plate. The systematic study has been carried out widely changing geometrical and rheological parameters of the system and testing the relative influence on the kinematics of subduction. A total number of 60 different experiments have been performed using variable combinations of thickness, viscosities, densities of the plate and mantle. We have scaled down our experiments to natural gravity field using silicone putty and honey to simulate the viscous behavior of slab and mantle, respectively. Our models can be divided in two classes typified by a different style of subduction: a "retreating" style of subduction characterized by the backward motion of the trench and the slow advancing motion of the plate, and an "advancing" style, where trench is stationary or advance towards the upper plate and the plate move in faster way. The latter condition is found to be more difficult to be obtained. In general terms, the two behaviors depend upon the distribution of the forces active into the system. If driving forces are much more elevated than resisting ones the system is more prone to retreat. The result we obtained in terms of velocity of subduction, in addition, is original with respect to previous works. We found a velocity of subduction which is always much greater than the one calculated by using simple equations. Hence we pointed out that a precise evaluation of subduction velocity could not be done assuming a constant radius of curvature
Dynamics of subduction and plate motion in laboratory experiments : insights into the "plate tectonics" behavior of the Earth
No full textInternational audienceThree-dimensional laboratory experiments have been designed to investigate the way slab-bearing plates move during subduction inside the mantle. In our experiments a viscous plate of silicone (lithosphere) subducts under its negative buoyancy in a viscous layer of pure honey (mantle). Varying thickness, width, viscosity, and density of the plate and mantle, three characteristic modes of subduction are observed: a retreating trench mode (mode I), a retreating trench mode following a transient period of advancing trench (mode II), and an advancing trench mode (mode III). These modes are characterized by different partitioning of the amount of subduction into plate and trench motion. Our experiments show that the velocity of subduction can be modeled by the dynamic interaction between acting and resisting forces, where lithospheric bending represents 75-95% of the total resisting forces. However, our experimental results also show the impossibility to predict a priori the plate velocity only from the velocity of subduction without considering trench migrations. We find experimentally that the lithospheric radius of curvature, which depends upon plate characteristics (stiffness and thickness) and the mantle thickness, exerts a primary control on the trench behavior. Our results suggest that the complexity of the style of subduction could be controlled by geometrical rules of a plate bending inside a stratified mantle. The Earth system is in the crucial range for the interplay between the rigidity of the plate and the mantle stratification: this setting may be the responsible for the complexity of the past and present tectonic styles
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
