1,720,981 research outputs found
Reliability of source parameters for small events in central italy: Insights from spectral decomposition analysis applied to both synthetic and real data
No full textWe apply a spectral decomposition approach to isolate the source spectra from propagation and site effects and, in turn, to estimate the source parameters of small-to-moderate earthquakes that occurred in central Italy. The data set is composed of about 400,000 waveforms relevant to 4111 earthquakes in the moment magnitude range 1.5–6.5, recorded by a high-density network of stations installed in the study area. We first investigate the reliability of the source parameters for small magnitudes through numerical simulations. We generate synthetic spectra for different source scaling models and near-surface attenuation effects, considering the source–station geometry and the data availability of the central Italy data set. Our analysis with synthetics shows that the spectral decomposition is effective in isolating the source contributions from other factors. Moreover, the analysis of the residual distributions suggests that moment magnitude 1.8 is the lower bound for the retrieval of reliable Brune’s source parameters, although we observe an increase of residual’s variability below magnitude 3, and the estimated source parameters could be biased below magnitude 2.3. Remarkably, the assessment of the stress drop Δσ for small events is strongly hampered by site-specific attenuation near the surface. In view of the results with synthetics, we analyze the source parameters of earthquakes recorded in central Italy. The corner frequency versus seismic moment relationship describes a source scaling in which Δσ increases with increasing moment magnitude Mw, the mean Δσ varying from 0.1 MPa for Mw 5. In particular, Δσ increases mainly for Mw in the ranges 2.5–3 and 4.5–5.2. The corner frequencies estimated from the apparent source spectra do not show any dependence on hypocentral distance and magnitude, confirming that uncorrected anelastic attenuation effects do not significantly bias the results
Reliability of the automatic procedures for locating earthquakes in South Western Alps and Northern Apennines (Italy)
No full text
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
Empirical Ground-Motion Prediction Equations for Northern Italy Using Weak- and Strong-Motion Amplitudes, Frequency Content, and Duration Parameters
No full textAbstract
The goals of this work are to review the Northern-Italy ground-motion
prediction equations (GMPEs) for amplitude parameters and to propose new GMPEs
for frequency content and duration parameters. Approximately 10,000 weak and
strong waveforms have been collected merging information from different neighbor-
ing regional seismic networks operating in the last 30 yr throughout Northern Italy.
New ground-motion models, calibrated for epicentral distances ≤ 100 km and for both
local (ML ) and moment magnitude (Mw ), have been developed starting from a high
quality dataset (624 waveforms) that consists of 82 selected earthquakes with ML and
Mw up to 6.3 and 6.5, respectively. The vertical component and the maximum of the
two horizontal components of motion have been considered, for both acceleration
(peak ground horizontal acceleration [PGHA] and peak ground vertical acceleration
[PGVA]) and velocity (peak ground horizontal velocity [PGHV] and peak ground ver-
tical velocity [PGVV]) data. In order to make comparisons with the most commonly
used prediction equations for the Italian territory (Sabetta and Pugliese, 1996 [here-
after, SP96] and Ambraseys et al. 2005a,b [hereafter, AM05]) the coefficients for ac-
celeration response spectra (spectral horizontal acceleration [SHA] and spectral
vertical acceleration [SVA]) and for pseudovelocity response spectra (pseudospectral
horizontal velocity [PSHV] and pseudospectral vertical velocity [PSVV]) have been
calculated for 12 periods ranging between 0.04 and 2 sec and for 14 periods ranging
between 0.04 and 4 sec, respectively. Finally, empirical relations for Arias intensities
(IA), Housner intensities (IH), and strong motion duration (DV) have also been cali-
brated. The site classification based on Eurocode (hereafter, EC8) classes has been
used (ENV, 1998, 2002). The coefficients of the models have been determined using
functional forms with an independent magnitude decay rate and applying the random
effects model (Abrahamson and Youngs, 1992; Joyner and Boore, 1993) that allow the
determination of the interevent, interstation, and record-to-record components of vari-
ance. The goodness of fit between observed and predicted values has been evalu-
ated using the maximum likelihood approach as in Spudich et al. (1999). Comparing
the proposed GMPEs with SP96 and AM05, it is possible to observe a faster decay of
predicted ground motion, in particular for distances greater than 25 km and magni-
tudes higher than 5.0. The result is an improvement in fit of about one order of size for
magnitudes spanning from 3.5 to 4.5
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