1,720,983 research outputs found
Fast and accurate determination of earthquake moment, rupture length and stress release for the 2016-2017 Central Italy seismic sequence
No full textEarthquake Seismic Moment, Rupture Radius, and Stress Drop from P-Wave Displacement Amplitude Versus Time Curves
No full textThe reliable determination of earthquake source parameters is a relevant task of seismological investigations which ground nowadays on high-quality seismic waveforms collected by near-source dense arrays of ground motion sensors. Here, we propose a parametric modeling technique which analyzes the time-domain P-wave signal recorded in the near-source range of small-to-large-size earthquakes. Assuming a triangular moment rate function, a uniform speed, and circular rupture model, we develop the equations to estimate the seismic moment, rupture radius, and stress drop from the corner time and plateau level of the average logarithm of the P-wave displacement versus time curves (LPDT). The constant- Q , anelastic attenuation effect, is accounted by a postprocessing procedure that evaluates the Q -unperturbed moment rate triangular shape. The methodology has been validated through application to the acceleration records of the 2016-2017 Central Italy and 2007-2019 Japan earthquake sequences covering a wide moment magnitude range (Mw 2.5-6.5) and recording distance <100 km. After correcting for the anelastic attenuation function, the estimated average stress drop and the confidence interval ( langle Delta sigma
angle =0.60 (0.42-0.87) MPa and langle Delta sigma
angle =1.53 (1.01-2.31) for crustal and subcrustal events of Japan and langle Delta sigma
angle =0.36 (0.30-0.44) MPa for Central Italy) show for both regions a self-similar, constant stress drop scaling of the rupture duration/radius with seismic moment. The smaller sensitivity of the spatially averaged, time-varying peak displacement amplitude to the radiation from localized high slip patch on the fracture surface could explain the retrieved smaller average stress drops for subcrustal earthquakes in Japan and M >5.5 events in Central Italy relative to previous estimates using spectral methods
Quick determination of the earthquake focal mechanism from the azimuthal variation of the initial P-wave amplitude
No full textWhen an earthquake occurs, a key parameter in the emergency’s management is the knowledge of the most stressed areas by the ground motion. The focal mechanism is an essential source parameter for producing realistic shake maps. Although the approaches for estimating earthquake location and magnitude are now consolidated, automatic solutions for the focal mechanism are not always provided by the agencies or available at later times after inversion of waveforms for the determination of moment tensor components. We introduce a new approach for the automatic determination of the earthquake focal mechanism, using the spatial distribution of observed absolute initial P-wave peak amplitudes, corrected for the geometrical attenuation effect, in an evolutionary, Bayesian framework. We applied the proposed methodology to the main earthquakes of the 2016–2017 central Italy seismic sequence finding that our rapid automatic estimates of the focal mechanism are in good agreement with those of the reference solutions
Retrospective performance analysis of a ground shaking early warning system for the 2023 Turkey–Syria earthquake
Full text linkRecently developed earthquake early warning systems rely on the idea of combining the measured ground motion and the source parameter estimate to issue an alert based on the ground shaking prediction at sites where high potential damage is expected. Here we apply a P-wave, shaking-forecast method that can track and alert in real-time the area where peak ground motion is expected to exceed a user-set threshold during the earthquake. The system performance in providing a fast and reliable warning during the Mw 7.8, February 6 Turkey–Syria earthquake is investigated by the real-time simulated playback of the near-source hundred accelerograms. With an instrumental intensity threshold
an alert issued 10–20 s after the event origin, results in 95% of successful warning (positive and negative) and lead-times of 10–60 s within the potential damage zone. Setting a higher intensity threshold requires larger alert times (50–60 s) to achieve 90% of successful warning and overall shorter lead-times. Our simulation shows that the P-wave predicted, strong-shaking zone can be rapidly detected only 20 s after the mainshock nucleation. As the time increases, it well delineates the NE-SW bi-lateral rupture development as inferred by kinematic source models
Source parameters of moderate-to-large Chinese earthquakes from the time evolution of P-wave peak displacement on strong motion recordings
Full text linkIn this work we propose and apply a straightforward methodology for the automatic characterization of the extended earthquake source, based on the progressive measurement of the P-wave displacement amplitude at the available stations deployed around the source. Specifically, we averaged the P-wave peak displacement measurements among all the available stations and corrected the observed amplitude for distance attenuation effect to build the logarithm of amplitude vs. time function, named LPDT curve. The curves have an exponential growth shape, with an initial increase and a final plateau level. By analyzing and modelling the LPDT curves, the information about earthquake rupture process and earthquake magnitude can be obtained. We applied this method to the Chinese strong motion data from 2007 to 2015 with Ms ranging between 4 and 8. We used a refined model to reproduce the shape of the curves and different source models based on magnitude to infer the source-related parameters for the study dataset. Our study shows that the plateau level of LPDT curves has a clear scaling with magnitude, with no saturation effect for large events. By assuming a rupture velocity of 0.9 Vs, we found a consistent self-similar, constant stress drop scaling law for earthquakes in China with stress drop mainly distributed at a lower level (0.2 MPa) and a higher level (3.7 MPa). The derived relation between the magnitude and rupture length may be feasible for real-time applications of Earthquake Early Warning systems
Design, Implementation and Testing of a Network-Based Earthquake Early Warning System in Greece
Full text linkIn this study we implemented and tested the Earthquake Early Warning system PRESTo (PRobabilistic and Evolutionary early warning System, Satriano et al., 2011) on the Greek Ionian islands of Lefkada, Zakynthos and Kefalonia. PRESTo is a free and open source platform for regional Earthquake Early Warning developed at the University of Naples Federico II, which is currently under experimentation in Southern Italy, in the area covered by the Irpinia Seismic Network. The three Ionian islands selected for this study are located on the North-Western part of the Hellenic trench. Here the seismicity rate and the seismic hazard, coupled with the vulnerability of existing critical infrastructures, make this region among the highest seismic risk areas in Europe, where the application of Earthquake Early Warning systems may become a useful strategy to mitigate the potential damage caused by earthquakes. Here we studied the feasibility of implementing an Earthquake Early Warning system on an existing seismic network, which was not specifically made for earthquake early warning purposes, and evaluated the performance of the system, using a data set of real-earthquake recordings. We first describe the technical details of the implementation of PRESTo in the area of interest, including the preliminary parameter configuration and the empirical scaling relationship calibration. Then we evaluated the performance of the system through the off-line analysis of a database of real earthquake records belonging to the most recent M > 4.0 earthquakes occurred in the area. We evaluated the performance in terms of source parameter estimation (location, magnitude), accuracy of ground shaking prediction and lead-time analysis. Finally, we show the preliminary results of the real-time application of PRESTo, performed during the period 01–31 July 2019
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
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