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Back-projection analysis of P waves emitted by Maule earthquake (Chile, 27/02/2010, Mw 8.8) using dynamic station corrections
No full textHigh-frequency seismic emission during Maule earthquake (Mw 8.8, 27/02/2010) inferred from high-resolution backprojection analysis of P waves
No full textSince its first application on Sumatra-Andaman earthquake, back-projection analysis has been widely exploited
to infer the time-evolution of the rupture fronts of mega-earthquakes. In this technique, selected seismic phases
recorded at teleseismic distances by a network of sensors are shifted according to a possible source position and
a velocity model, and a multichannel version of the cross-correlation function is estimated. In this way, the timedependent
map of the seismic energy emission in the source area can be inferred.
We have back-projected the mainshock of Maule earthquake (Mw 8.8), which nucleated on 27/02/2010 in central
Chile and is one of the largest earthquakes recorded in modern times. We have analyzed P phases filtered in the
frequency range (0.4-3) Hz recorded by three seismic arrays located in US, Africa and Antarctica. Relative time
shifts between sensors (inferred by maximizing the cross-correlation function) have been estimated with respect
to a 1D global velocity model (ak135) and have been refined introducing two corrections, a static correction and
a dynamic correction. The former is the time shift induced by local effects in the sensor area, whereas the latter
is the correction associated with the source-sensor path and is mostly affected by medium properties in the source
area. We have inferred these two corrections by analyzing the waveforms of 23 aftershocks and foreshocks with
high magnitude (>5.3). In detail, static correction was chosen as the mean time shift averaged over all the events
recorded by one station, while dynamic correction was the remaining part of the travel time after removing the 1D
model travel time and the static correction. Moreover, dynamic corrections (and hence the complete travel times)
have been interpolated over all the source area by Kriging, a spatial interpolation method.
Results show that high-frequency seismic energy emission mostly occurs along the coastline with a general northward
migration during the event. Specifically, in the first minute of the rupture process, the energy emission occurs
southerly from or close to the epicenter. Afterwards, seismic emission moves northwards, with a gap with respect
to the first emission zone, and a further northward migration occurs till the end of emission. Both the spatial gap of
seismic emission and the northward migration are in line with the results of other studies in the same area, whereas
we find a shallower emission area and different emission features in the zone close to the epicenter. Results for
different frequency bands and the analysis of secondary maxima of energy emission are being investigated. In
particular, we are shifting towards higher frequencies looking at the frequency bands (1-4) Hz and (2-8) Hz. The
former band displays an emission pattern similar to that of (0.4-3) Hz, but with a sharper gap of about 50 Km; the
latter band shows coherent arrivals only during the first 80 s, with a clear energy emission south of the epicenter at
the onset of the event and preserving the northward migration afterwards
High-frequency seismic radiation from Maule earthquake (Mw 8.8, 27/02/2010) inferred from high-resolution backprojection analysis
No full textThe Maule earthquake (2010 February 27, Mw 8.8, Chile) broke the subduction megathrust along a previously locked segment. Based on an international aftershock deployment, catalogues of precisely located aftershocks have become available. Using 23 well-located aftershocks, we calibrate the classic teleseismic backprojection procedure to map the high-frequency seismic radiation emitted during the earthquake. The calibration corrects traveltimes in a standard earth model both with a static term specific to each station, and a ‘dynamic’ term specific to each combination of grid point and station. The second term has been interpolated over the whole slipping area by kriging, and is about an order of magnitude smaller than the static term. This procedure ensures that the teleseismic images of rupture development are properly located with respect to aftershocks recorded with local networks and does not depend on accurate hypocentre location of the main shock.
We track a bilateral rupture propagation lasting ∼160 s, with its dominant branch rupturing northeastwards at about 3 km s−1. The area of maximum energy emission is offset from the maximum coseismic slip but matches the zone where most plate interface aftershocks occur. Along dip, energy is preferentially released from two disconnected interface belts, and a distinct jump from the shallower belt to the deeper one is visible after about 20 s from the onset. However, both belts keep on being active until the end of the rupture. These belts approximately match the position of the interface aftershocks, which are split into two clusters of events at different depths, thus suggesting the existence of a repeated transition from stick-slip to creeping frictional regime
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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