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Deciphering seismic response of landslide-prone slopes from reconnaissance microtremor measurements with a broad-band velocimeter
No full textRecent experimental studies have pointed out that susceptibility of slopes to seismically induced failures can be significantly increased by site conditions determining phenomena of directional resonance along potential sliding directions. Evidence of such situations were obtained from long-term accelerometric monitoring conducted in central Italy (Caramanico Terme), and it has been suggested that similar phenomena may have influenced also some of the giant landslides triggered in Taiwan by the 1999 Chi-Chi earthquake. Since factors controlling directional resonance are still unclear, it is of great interest to develop reconnaissance techniques capable to point out the occurrence of conditions of site response directivity. One promising technique is based on the analysis of the azimuthal variations of the spectral ratios between horizontal and vertical component of noise recordings (HVNR), derived from microtremors measured with portable velocimeters. At this regard an extension of observations to low frequency spectral ratios, even below 1 Hz, is desirable, especially in the case of very large landslides whose stability conditions under seismic shaking could be more sensitive to the effect of larger wavelengths. For this reason we tested the employment of a portable broad-band sensor for HVNR measurements on landslide-prone slopes. First, measurements previously carried out at Caramanico with different seismometric sensors were repeated for comparative purposes. Then, data acquisition was extended to other sites in the same area and in two areas of Taiwan, on the giant landslides of Tsaoling and Jiufengershan. It is recognized that the analysis of noise recording on a broader frequency bandwidth poses some supplementary difficulties for the presence of strong low frequency signals that vary with atmospheric and sea conditions. However, the measurements obtained at Caramanico showed that, where clear site response directivity had been revealed by previous observations, the results of HVNR analysis derived from broad-band measurements were consistent with those derived by other type of sensors. At other Caramanico sites, HVNR analysis of the broad-band data provided uncertain results, possibly as effect of variable conditions of data acquisition that might obscure weaker site response effects. In some cases the repeatability of the results was a problem, possibly due to temporary action of a local source of strong polarised noise. The measurements obtained in Taiwan in the two giant landslide areas, both characterised by mass movements occurred along bedding surface, revealed the presence of abnormally high values of HVNR for sites on slip surfaces, with a very strong directional variation through a large frequency band and with pronounced maxima at frequency less than 1-2 Hz, i.e. at frequencies influenced by signals of atmospheric and marine origin. Although the recordings on nearby sites on the flanks or the crowns of the landslides did not reveal similar properties, the representativeness and exact significance of the HVNR data acquired on the slip surfaces need to be more deeply investigated in order to exclude the effects of anomalous acquisition conditions. More in general, contemporaneous measurements of noise with two different types of instruments at different times and varying environmental conditions should help to clarify to what extent the reconnaissance type of noise measurements by broad-band instruments could be useful for detecting directivity in seismic site respons
Test of microtremor measurements with a broad-band sensor for the characterisation of seismic response of landslide prone scope
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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