1,720,991 research outputs found
Experimental Tectonics: Convergent Margins from a Lithosphere–Mantle Perspective
No full textAbstract Experimental modeling is a methodology used for a wide range of scientific applications, including the study of tectonic processes. This contribution is devoted to provide an overview of laboratory models realized to understand the physics behind the behavior of convergent margins at the mantle scale, focusing on the overall process controlled by the lithosphere–mantle interaction
Denoising daily displacement GNSS time series using deep neural networks in a near real-time framing: a single-station method
No full textRecent ground observations from Global Navigation Satellite Systems (GNSS) displacement time-series have provided compelling evidence that the tectonic motion in many settings is ubiquitously non-steady-state. In some cases, these anomalous transient motions have been identified as potential precursors occurring months, days, or hours before large-magnitude earthquakes. However, effectively detecting these signals in daily geodetic time series at the earliest opportunity remains challenging due to the levels of high-frequency noise. Currently, there is a lack of established methodologies to reduce this noise in near-real-time thereby hindering our ability to promptly monitor tectonic transient motions. Precursors are typically modelled retrospectively, and the use of geodetic data for seismic hazard surveillance remains limited. To address this limitation, this study demonstrates an approach to model high-frequency noise in daily GNSS displacement time series, with the removal of this modelled noise allowing for tectonic transients to be potentially more clearly identified. Using Deep Neural Networks (DNNs), we develop a denoising approach that removes noise from GNSS displacement time series on a station-by-station basis. To more effectively train our DNN models, we generate a comprehensive and diverse data set by combining synthetic trajectories with synthetic noise time series created using Generative Adversarial Networks (GAN). To train the GAN, we use noise time series extracted from ~5000 GNSS displacement time series distributed globally. Validating our approach with real data confirms its capability to significantly reduce the high-frequency noise that characterizes GNSS time series. The flexibility of the method allows for near-real-time noise removal (with a latency of a few days), opening up the possibility of detecting and modelling small tectonic transients in a timely fashion. By introducing this novel approach, we present exciting opportunities to advance the geodetic surveillance of tectonic motions and usher in a new era of improved monitoring of seismic activity
The surface tectonics of mantle lithosphere delamination following ocean lithosphere subduction: Insights from physical-scaled analogue experiments
Full text linkMany postulated lithospheric removal events occur in regions with an earlier history of subduction, but the relationship between the two processes has not been explored. In this work, we use physical-scaled analogue experiments to investigate the evolution from ocean lithosphere subduction to collision and possible delamination of the mantle lithosphere from the crust. We test how varying the magnitude of plate convergence alters the behavior of the subduction-delamination model. Our experiments show that a retreating ocean proplate can evolve to continental mantle lithosphere delamination. Negative surface topography is supported at the delamination hinge, and this migrates back with the peeling lithosphere. With high plate convergence, delamination is suppressed. Rather, the crust and mantle lithosphere split at the collision zone in a form of flake tectonics as oncoming procrust is accreted on top of the retroplate and the promantle lithosphere subducts below. Localized high topography develops at this zone of crustal accretion and thickening. The results suggest that delamination may be a continental continuation of plate retreat and that lithospheric removal is triggered by the transition from one process to another.Natural Sciences and Engineering Research Council of CanadaThis work was supported by the Natural Sciences and Engineering Research Council of Canada. We thank Alexander Cruden, Pierre Robin, and Francesca Funiciello for insightful discussion and suggestions that have also improved our work. We appreciate careful and thoughtful reviews by Eugene Humphreys and Randell Stephenson
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
The seismic cycle at subduction thrusts: 2. Dynamic implications of geodynamic simulations benchmarked with laboratory models
No full textVariations 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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