1,721,105 research outputs found
Stress changes, focal mechanisms, and earthquake scaling laws for the 2000 dike at Miyakejima (Japan)
Full text linkFaulting processes in volcanic areas result from a complex interaction of pressurized fluid‐filled cracks and conduits with the host rock and local and regional tectonic setting. Often, volcanic seismicity is difficult to decipher in terms of the physical processes involved, and there is a need for models relating the mechanics of volcanic sources to observations. Here we use focal mechanism data of the energetic swarm induced by the 2000 dike intrusion at Miyakejima (Izu Archipelago, Japan), to study the relation between the 3‐D dike‐induced stresses and the characteristics of the seismicity. We perform a clustering analysis on the focal mechanism (FM) solutions and relate them to the dike stress field and to the scaling relationships of the earthquakes. We find that the strike and rake angles of the FMs are strongly correlated and cluster on bands in a strike‐rake plot. We suggest that this is consistent with optimally oriented faults according to the expected pattern of Coulomb stress changes. We calculate the frequency‐size distribution of the clustered sets finding that focal mechanisms with a large strike‐slip component are consistent with the Gutenberg‐Richter relation with a b value of about 1. Conversely, events with large normal faulting components deviate from the Gutenberg‐Richter distribution with a marked roll‐off on its right‐hand tail, suggesting a lack of large‐magnitude events (Mw > 5.5). This may result from the interplay of the limited thickness and lower rock strength of the layer of rock above the dike, where normal faulting is expected, and lower stress levels linked to the faulting style and low confining pressure
Earthquake catalogs for: Improving detection of micro-earthquakes in the Val d'Agri region (Southern Italy) using Deep Learning algorithms
No full textThis repository contains two earthquake catalogs (dubbed PRN and QS) obtained from the application of two deep-learning-based detection workflows to continuous seismic data recorded in the Val d’Agri region (Southern Italy). These catalogs have been generated using the PhaseNet neural network for seismic phase picking (Zhu & Beroza, 2019). The workflows used to generate the catalogs are described in detail in: Caredda et al. (2025). These datasets offer a more comprehensive representation of local seismicity compared to manually generated, STA/LTA-based catalogs (available in the open periodic monitoring reports accessible at: https://cms.ingv.it/sperimentazioni/val-d-agri [last accessed on 18/09/2025]).
The datasets include event origin times, locations, magnitudes, location uncertainties, and phase arrival times with corresponding PhaseNet “pick probabilities” (for the PRN catalog), providing an enriched representation of local seismicity compared to conventional STA/LTA-based catalogs.
These catalogs can serve as valuable resources for further research on seismicity, induced processes, Earth structure, and seismic hazard assessment in the Val d’Agri region.
References:
Caredda, E., M.P. Isken, S. Cesca, M. Errico, G. Zerbinato, and A. Morelli (2025) Improving detection of micro-earthquakes in the Val d’Agri region (Southern Italy) using deep learning algorithms, Seismica (in press).
Zhu, W., and Beroza, G. C. (2018). PhaseNet: A Deep-Neural-Network-Based Seismic Arrival Time Picking Method. Geophysical Journal International, 216(1), 261–273. https://doi.org/10.1093/gji/ggy42
Noise Analysis of Distributed Acoustic Sensing (DAS) Data in Borehole Installations
No full textDistributed acoustic sensing (DAS) is a technology that is revolutionizing seismic data acquisition, particularly in borehole installations. Acting as a dense array of receivers, DAS provides high coverage, revealing time‐depth patterns that are often hidden in data acquired with traditional seismometers. Its resilience to extreme temperature and pressure conditions, in which standard instrumentation typically fails, makes DAS reliable for microseismic monitoring operations in deep boreholes in geothermal environments. However, DAS faces challenges such as a lower signal‐to‐noise ratio compared to conventional geophones. DAS requires advanced denoising workflows in environments with high background noise, for example, from anthropogenic activities. A broader understanding and characterization of the noise observed in optical fibers is thus necessary and is still lacking. In this work, we aim to address this gap by analyzing noise data acquired from a fiber‐optic cable installed in a monitoring well at the Utah Frontier Observatory for Research in Geothermal Energy Enhanced Geothermal System pilot project site in southcentral Utah, United States. Our proposed workflow combines power spectral density and phase analysis to assess the modulation of noise over time and depth for different frequencies and consequently to differentiate noise originating by anthropogenic sources at the surface from those further away from the industrial site. In addition, our analysis highlights noise components that may be related to instrumental noise from the interrogator, contributing to future noise mitigation strategies. This is further demonstrated through a direct comparison with noise observed by geophones coupled with the optical fiber in the same monitoring well
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
Noise analysis of Distributed Acoustic Sensing (DAS) systems in borehole installations
No full textIn recent years, there has been an increasing interest in Distributed Acoustic Sensing (DAS) technology for microseismic monitoring, especially in operations involving borehole installations. Despite the widespread adoption of DAS systems in such contexts, many questions regarding the data quality of the recordings are still open. Is the DAS self-noise higher than traditional systems? How does the ambient noise recorded by a DAS system attenuate with the depth as observed with traditional geophones? It is known that various noise types, including optical, thermal, and mechanical noise coupled with the fiber, affect DAS data. Additionally, the noise frequency band often overlaps with the signal frequency band, making frequency filtering alone inadequate for denoising. Therefore, specialized noise reduction workflows, such as FK Filtering and SVD, are necessary. Mitigating the impact of noise on DAS data remains a primary challenge for the seismological and geophysical community. This study aims to examine and characterize the noise influencing DAS data collected in borehole installations, with a specific focus on the data recorded at the Frontier Observatory for Research in Geothermal Energy site in Utah, USA. We use Power Spectral Density analysis to assess depth-dependent noise reduction and its temporal variations. Furthermore, the depth dependence of the signal-to-noise ratio for various microseismic events is evaluated. Finally, a comparison is drawn with geophones data colocated with the fiber, offering a comprehensive exploration of the advantages and disadvantages of the two data acquisition technologies
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