Time-dependent Fisher Information Measure of volcanic tremor before the 5 April 2003 paroxysm at Stromboli volcano,Italy     

Luciano Telesca  Michele Lovallo  Roberto Carniel 《Journal of Volcanology and Geothermal Research》2010

The investigation of the time dynamics of volcanic tremor recorded at Stromboli volcano before the paroxysm occurred on April 5, 2003 was performed, on the base of a new approach, the Fisher Information Measure (FIM), which allows to detect changes in the dynamical behavior of a complex system. The particular observed pattern suggests that the signal varies between sets of disordered states (small FIM) and sets of ordered states (large FIM). Significant precursory changes in the temporal variation of the FIM were revealed at least 42 h before the paroxysm and lasting about 17 h. The timescales highlighted are compatible to those found by other authors and could qualify the FIM as a good detector of regime changes and possible precursors of anomalous volcanic activity.  相似文献   

A comparison of surface and underground array measurements of ambient noise recorded in Naples (Italy)     

Rosalba Maresca  Norma Damiano  Lucia Nardone  Mauro A. Di Vito  Francesca Bianco 《Journal of Seismology》2014,18(3):385-400

In this study, we describe two experiments of seismic noise measurements carried out in Naples, Italy. The site allowed measurements to be obtained both at the surface and in a tunnel that is 120-m-deep. The main goal was to compare the seismic response evaluated at the surface to the in-tunnel response, through spectral, polarization, and resonance directivity analyses. In the 1 to 20 Hz frequency band, the noise level was up to 15 dB higher at the surface than in the tunnel. The polarization properties and horizontal-to-vertical spectral ratios appear not to be influenced by the tunnel geometry or by the topography. Some preferential alignments were observed in the polarization azimuths computed at the surface, which are likely to be due to local sources, rather than morphological features. The absence of directivity effects and the low noise levels in the tunnel make this site suitable for installing seismic stations. We also studied how the subsoil structure affects the seismic motion at the surface. The dispersive properties of the Rayleigh waves were investigated using the spatial autocorrelation method. A joint inversion of the dispersion data and the horizontal-to-vertical spectral ratios provided the subsurface Vs profile. The derived model has a low velocity contrast at depth, such as to generate moderate and broad H/V spectral ratio peak amplitude. The normalized spectral ratio appears more appropriate to identify the soil-resonance frequencies.  相似文献   

Comparing seismicity declustering techniques by means of the joint use of Allan Factor and Morisita index     

Luciano Telesca  Michele Lovallo  Jean Golay  Mikhail Kanevski 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(1):77-90

In this paper, we propose to compare different declustering methods on the basis of the time-correlation and the space-clustering of the residual earthquake catalog after the declustering techniques have been applied. To this aim, we applied two point process clustering measures, the Allan Factor and the Morisita Index, for the identification and quantification of temporal correlation and spatial clustering in point processes, respectively. We used our joint space–time approach to study the earthquake space–time point processes of southern California and Switzerland with surrounding area, declustered by using the method of Gardner and Knopoff (with Grünthal and Uhmhammer window) and that of Reasenberg (with different setting parameters). Our results show that the residual declustered catalog is still characterized by time-correlated structures at long timescales; however, the cutoff timescale that is the lowest timescale above which the time-correlation is visible is higher with the Reasenberg method while is smaller with the Gardner and Knopoff method with Grünthal window. The space-clustering analysis performed by means of the Morisita Index suggests that the declustering technique effectively reduces the spatial clustering of the seismicity of Switzerland, but does not change the spatial properties of the residual seismic catalogue of the southern California.  相似文献   

Suitability of energy cone for probabilistic volcanic hazard assessment: validation tests at Somma-Vesuvius and Campi Flegrei (Italy)     

Pablo Tierz  Laura Sandri  Antonio Costa  Lucia Zaccarelli  Mauro Antonio Di Vito  Roberto Sulpizio  Warner Marzocchi 《Bulletin of Volcanology》2016,78(11):79

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Robust identification of periodic behavior in the time dynamics of short seismic series: the case of seismicity induced by Pertusillo Lake,southern Italy     

Luciano Telesca  Alessandro Giocoli  Vincenzo Lapenna  Tony Alfredo Stabile 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(5):1437-1446

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Discriminating Between Different Streamflow Regimes by Using the Fisher-Shan Method: An Application to the Colombia Rivers     

Jorge O. Pierini  Juan C. Restrepo  Michele Lovallo  Luciano Telesca 《Acta Geophysica》2015,63(2):533-546

The Fisher-Shannon (FS) information plane, defined by the Fisher information measure (FIM) and the Shannon entropy power (N_X), was robustly used to investigate the complex dynamics of eight monthly streamflow time series in Colombia. In the FS plane the streamflow series seem to aggregate into two different clusters corresponding to two different climatological regimes in Colombia. Our findings suggest the use of the statistical quantity defined by the FS information plane as a tool to discriminate among different hydrological regimes.  相似文献   

The “Pomici di mercato” Plinian eruption of Somma-Vesuvius: magma chamber processes and eruption dynamics     

M. Aulinas  L. Civetta  M. A. Di Vito  G. Orsi  D. Gimeno  J. L. Férnandez-Turiel 《Bulletin of Volcanology》2008,70(7):825-840

The Pomici di Mercato (PdM, 8,010 ± 40 a), also known in the literature as Pomici Gemelle or Pomici di Ottaviano, is one of the oldest Plinian eruptions of Somma-Vesuvius. This eruption occurred after the longest (7 ka) quiescence period of the volcano and was followed by more than 4 ka of repose. The erupted magma is phonolitic in composition. All the products have very low phenocrysts content (less than 3%) and show evidence of mineralogical disequilibria. They contain K-feldspar ± clinopyroxene (salite and diopside) ± plagioclase ± garnet ± biotite ± amphibole ± apatite ± Fe-Ti oxides. Pumice fragments collected at different stratigraphic heights are slightly less evolved and more enriched in radiogenic Sr composition upsection. The glass composition is fairly homogeneous in single pumice fragment and among pumice fragments from different layers. Glass separated from pumice fragments collected at different stratigraphic heights is homogeneous in the Sr-isotope composition (around a value of 0.70717). Glass is in isotopic equilibrium with salite throughout the entire sequence and with diopside at the base of the sequence. Diopside becomes more radiogenic upsection, reaching a value of 0.707458 ± 7, whereas feldspar is consistently slightly less radiogenic than glass. Nd-isotope composition is fairly uniform (ca. 0.51247) through the whole sequence. The isotopic disequilibria among glass, feldspar and diopside, together with the homogeneous isotopic composition of pumice glass in equilibrium with salite, and the mineralogical disequilibria between plagioclase and K-feldspar, imply that most of the diopside and plagioclase crystals are xenocrysts incorporated into the phonolitic magma during residence in a magma chamber and/or during ascent towards the surface. The PdM Tephra are compositionally and isotopically similar to the phonolitic, first-erupted products of the subsequent Pomici di Avellino Plinian eruption. On the basis of this similarity, we suggest that the magma feeding both eruptions resulted from the tapping of a unique magma chamber. Prior to the PdM eruption, this chamber was formed by a large and homogeneous phonolitic magma body. After the PdM eruption, as a consequence of new arrivals of more radiogenic in Sr, less-differentiated magma batches, the magma chamber progressively developed a slightly stratified phonolitic uppermost portion, capping a tephriphonolitic layer, both emitted during the subsequent Pomici di Avellino eruption.  相似文献   

Robust Statistical Methods to Discriminate Extreme Events in Geoelectrical Precursory Signals: Implications with Earthquake Prediction     

Cuomo  V.  Di Bello  G.  Lapenna  V.  Piscitelli  S.  Telesca  I.  Macchiato  M.  Serio  C. 《Natural Hazards》2000,21(2-3):247-261

In this study, we propose a robuststatistical method to discern anomalous patternsin geoelectrical time series measured in a seismicarea of the Southern Apennine chain. First, a filteringprocedure to remove seasonal effects related tometeo-climatic fluctuations was carried out.Then, we selected an autoregressive model able todescribe the time fluctuations of geoelectricalsignals and propose a method to obtain an objectiveestimate of probability of occurrence for each extremeevent detected in the time series. Our applications inSouthern Italy allow us to hypothesize that theambiguity of short-term prediction is within thecomplicated dynamics of the physical processresponsible for electrical anomalies observed on theearth's surface.  相似文献   

The influence of roughness geometry and Shields parameter on flow resistance in gravel-bed channels     

Giorgio Baiamonte  Vito Ferro 《地球表面变化过程与地形》1997,22(8):759-772

The spatial variability of bed particles of a gravel-bed channel is analysed and treated experimentally in order to simulate the effects of the arrangement of coarse bed elements on the flow resistance law. For the studied bed patterns, characterized by the concentration Γ of coarser elements arranged on the bed layer, a particle arrangement parameter α is proposed. The α parameter is useful for estimating the intercept b₀ of the semi-logarithmic flow resistance law deduced by flume measurements carried out for the hydraulic condition of large-scale and transition roughness. The differences between the experimental friction factor parameter values and the ones calculated by the proposed semi-logarithmic relationship are explained by the ratio between the Shields parameter and its critical value. The analysis shows that estimates of the friction factor parameter are not improved by introducing the Froude number into the flow resistance law. © 1997 by John Wiley & Sons, Ltd.  相似文献   

Testing a new rill flow resistance approach using the Water Erosion Prediction Project experimental database     

Alessio Nicosia  Costanza Di Stefano  Vincenzo Pampalone  Vincenzo Palmeri  Vito Ferro  Mark A. Nearing 《水文研究》2019,33(4):616-626

In this paper, a recently theoretically deduced rill flow resistance equation, based on a power‐velocity profile, was tested using the Water Erosion Prediction Project database. This database includes measurements of flow velocity, water depth, cross section area, wetted perimeter, and bed slope that were made in rills shaped on experimental sites distributed across the continental United States. In particular, three different experimental conditions (only rainfall, only flow, and rain with flow) were examined, and for each condition, the theoretically based relationship for estimating the Γ function of the power velocity profile was calibrated. The results established that (a) the Darcy‐Weisbach friction factor can be accurately estimated using the proposed theoretical approach, and (b) the flow resistance increases with the effect of rainfall impact.  相似文献