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  • 1
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    Geotechnical characterization of the upper Pleistocene-Holocene alluvial deposits of Roma (Italy) by means of multivariate geostatistics: Cross-validation results (2009)
    Elsevier
    Details
    Publication Date: 2023-06-05
    Description: We are presenting an attempt to evaluate the spatial variability of geotechnical parameters in the upper Pleistocene–Holocene alluvial deposits of Roma (Italy) by means of multivariate geostatistics. The upper Pleistocene–Holocene alluvial deposits of Roma are sensitive to high levels of geohazard. They occupy a sizable and significant part of the city, being the foundation for many monuments, historical neighborhoods, and archaeological areas, and the main host of the present and future subway lines. We have stored information from more than 2000 geotechnical boreholes crossing the alluvial deposits into a relational database. For the present study, only the boreholes with lithologic/textural interpretation and geotechnical information were selected. The set includes 283 boreholes and 719 samples, which have a set of geotechnical information comprising physical properties and mechanical parameters. Techniques of multivariate statistics and geostatistics were combined and compared to evaluate the estimation methods of the mechanical parameters, with special reference to the drained friction angle from direct shear test (φ′). Principal Component Analysis was applied to the dataset to highlight the relationships between the geotechnical parameters. Through cross-validation analysis, multiple linear regression, kriging, and cokriging were tested as estimators of φ′. Cross-validation demonstrates that the cokriging with granulometries as auxiliary variables is the most suitable method to estimate φ′. In addition to proving that cokriging is a good estimator of φ′, cross-validation demonstrates that input data are coherent and this allows us to use them for estimation of geotechnical parameters, although they come from different laboratories and different vintages. Nevertheless, to get the same good results of cross-validation in estimation, it is necessary for granulometries to be available at grid points. Since this information being not available at all grid points, it is expected that, in the future, textural information can be derived in an indirect way, i.e., from lithologic/textural spatial reconstructions.
    Description: Published
    Description: 251-268
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: open
    Keywords: Alluvial deposits ; Geotechnical properties ; Principal Component Analysis ; Multivariate geostatistics ; Roma ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Statistical study of epicentre alignment in the broader Aegean area (2006)
    Details
    Publication Date: 2021-12-06
    Description: Accurate data concerning shallow (h = 60 km) earthquakes (Ms =4.5) that occurred in the broader Aegean area are used to point out the presence of linear seismogenic structures (seismolineaments). The earthquake data were analyzed by the use of a specific algorithm, and the directions of the best alignment of epicentres were found. The algorithm is based on statistical criteria applied within a circular area with the aim of searching for the best direction of alignment; this is then tested, to discriminate whether or not the pattern could stem from a random distribution of epicentres, or whether it is effectively the result of a linear seismic structure; the procedure is repeated to cover the whole area examined. The resulting lineaments can be regarded as individual tectonic units, as they usually coincide with known active faults or fault systems. An interpretation is given of the spatio-temporal evolution of the seismicity along the lineaments in terms of the asperity model.
    Description: JCR Journal
    Description: open
    Keywords: Aegean area ; epicentre ; seismolineament ; faults interaction ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 2805785 bytes
    Format: application/pdf
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  • 3
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    Recent AEM Case Study Examples of a Full Waveform Time-Domain System for Near-Surface and Groundwater Applications (2015)
    Details
    Publication Date: 2021-07-13
    Description: Early time or high frequency airborne electromagnetic data (AEM) are desirable for shallow sounding or mapping of resistive areas but this poses difficulties due to a variety of issues, such as system bandwidth, system calibration and parasitic loop capacitance. In an effort to address this issue, a continued system design strategy, aimed at improving its early-channel VTEM data, has achieved fully calibrated, quantitative measurements closer to the transmitter current turn-off, while maintaining reasonably optimal deep penetration characteristics. The new design implementation, known as “Full Waveform” VTEM was previously described by Legault et al. (2012). This paper presents some case-study examples of a Full Waveform helicopter time-domain EM system for near-surface applications
    Description: Published
    Description: EG31
    Description: 7A. Geofisica di esplorazione
    Description: N/A or not JCR
    Description: open
    Keywords: HTEM; data inversion; data processing; instrument implementation ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.01. Data processing ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Testing for ontological errors in probabilistic forecasting models of natural systems (2015)
    Details
    Publication Date: 2021-06-25
    Description: Probabilistic forecasting models describe the aleatory variability of natural systems as well as our epistemic uncertainty about how the systems work. Testing a model against observations exposes ontological errors in the representation of a system and its uncertainties. We clarify several conceptual issues regarding the testing of probabilistic forecasting models for ontological errors: the ambiguity of the aleatory/epistemic dichotomy, the quantification of uncertainties as degrees of belief, the interplay between Bayesian and frequentist methods, and the scientific pathway for capturing predictability. We show that testability of the ontological null hypothesis derives from an experimental concept, external to the model, that identifies collections of data, observed and not yet observed, that are judged to be exchange- able when conditioned on a set of explanatory variables. These conditional exchangeability judgments specify observations with well-defined frequencies. Any model predicting these behaviors can thus be tested for ontological error by frequentist methods; e.g., using P values. In the forecasting problem, prior predictive model checking, rather than posterior predictive checking, is desir- able because it provides more severe tests. We illustrate experi- mental concepts using examples from probabilistic seismic hazard analysis. Severe testing of a model under an appropriate set of experimental concepts is the key to model validation, in which we seek to know whether a model replicates the data-generating pro- cess well enough to be sufficiently reliable for some useful pur- pose, such as long-term seismic forecasting. Pessimistic views of system predictability fail to recognize the power of this method- ology in separating predictable behaviors from those that are not.
    Description: Published
    Description: 11973 – 11978
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: reserved
    Keywords: Bayesian statistics ; testing hazard models ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    Statistical analysis of the Central-Europe seismicity (2009)
    Elsevier B.V.
    Details
    Publication Date: 2021-06-16
    Description: The aim of this paper is to characterize the spatio-temporal distribution of Central-Europe seismicity. Specifically, by using a non-parametric statistical approach, the proportional hazard model, leading to an empirical estimation of the hazard function, we provide some constrains on the time behavior of earthquake generation mechanisms. The results indicate that the most conspic- uous characteristics of MW 4.0+ earthquakes is a temporal clustering lasting a couple of years. This suggests that the probability of occurrence increases immediately after a previous event. After a few years, the process becomes almost time independent. Furthermore, we investigate the cluster properties of the seismicity of Central-Europe, by comparing the obtained result with the one of synthetic catalogs generated by the epidemic type aftershock sequences (ETAS) model, which previously have been successfully applied for short term clustering. Our results indicate that the ETAS is not well suited to describe the seismicity as a whole, while it is able to capture the features of the short- term behaviour. Remarkably, similar results have been previously found for Italy using a higher magnitude threshold.
    Description: Published
    Description: 195-204
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Earthquake Distribution ; Earthquake Forecast ; Spatio-temporal statistical analysis ; Cluester ; Central Europe ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    Comparison of a new expert elicitation model with the Classical Model, equal weights and single experts, using a cross-validation technique (2012)
    Elsevier
    Details
    Publication Date: 2021-05-17
    Description: The problem of ranking and weighting experts' performances when quantitative judgments are being elicited for decision support is considered. A new scoring model, the Expected Relative Frequency model, is presented, based on the closeness between central values provided by the expert and known values used for calibration. Using responses from experts in five different elicitation datasets, a cross-validation technique is used to compare this new approach with the Cooke Classical Model, the Equal Weights model, and individual experts. The analysis is performed using alternative reward schemes designed to capture proficiency either in quantifying uncertainty, or in estimating true central values. Results show that although there is only a limited probability that one approach is consistently better than another, the Cooke Classical Model is generally the most suitable for assessing uncertainties, whereas the new ERF model should be preferred if the goal is central value estimation accuracy.
    Description: Published
    Description: 1292-1310
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: Expert elicitation ; Expert judgement ; Subjective probability ; Cross-validation ; Cooke Classical Model ; Expected Relative Frequency model ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
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    Stress releasemodel and proxy measures of earthquake size. Application to Italian seismogenic sources (2016)
    Elsevier Science Limited
    Details
    Publication Date: 2021-05-12
    Description: This study presents a series of self-correcting models that are obtained by integrating information about seismicity and fault sources in Italy. Four versions of the stress release model are analyzed, in which the evolution of the system over time is represented by the level of strain, moment, seismic energy, or energy scaled by the moment. We carry out the analysis on a regional basis by subdividing the study area into eight tectonically coherent regions. In each region, we reconstruct the seismic history and statistically evaluate the completeness of the resulting seismic catalog. Following the Bayesian paradigm, we apply Markov chain Monte Carlo methods to obtain parameter estimates and a measure of their uncertainty expressed by the simulated posterior distribution. The comparison of the four models through the Bayes factor and an information criterion provides evidence (to different degrees depending on the region) in favor of the stress release model based on the energy and the scaled energy. Therefore, among the quantities considered, this turns out to be the measure of the size of an earthquake to use in stress release models. At any instant, the time to the next event turns out to follow a Gompertz distribution, with a shape parameter that depends on time through the value of the conditional intensity at that instant. In light of this result, the issue of forecasting is tackled through both retrospective and prospective approaches. Retrospectively, the forecasting procedure is carried out on the occurrence times of the events recorded in each region, to determine whether the stress release model reproduces the observations used in the estimation procedure. Prospectively, the estimates of the time to the next event are compared with the dates of the earthquakes that occurred after the end of the learning catalog, in the 2003–2012 decade.
    Description: Italian Dipartimento della Protezione Civile in the framework of the 2007–2009 Agreement with Istituto Nazionale di Geofisica e Vulcanologia (INGV), project S1: Analysis of the seismic potential in Italy for the evaluation of the seismic hazard.
    Description: Published
    Description: 147-168
    Description: 2T. Tettonica attiva
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: point process ; probabilistic forecasting ; interevent time distribution ; seismogenic sources ; Bayesian inference ; 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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    Sensitivity analysis and uncertainty estimation for tephra dispersal models (2008)
    AGU
    Details
    Publication Date: 2020-11-30
    Description: Sensitivity analysis and uncertainty estimation are crucial to the validation and calibration of numerical models. In this paper we present the application of sensitivity analyses, parameter estimations and Monte-Carlo uncertainty analyses on TEPHRA, an advection-diffusion model for the description of particle dispersion and sedimentation from volcanic plumes. The model and the related sensitivity analysis are tested on two sub-plinian eruptions: the 22 July 1998 eruption of Etna volcano (Italy) and the 17 June 1996 eruption of Ruapehu volcano (New Zealand). Sensitivity analyses are key to (i) constrain crucial eruption parameters (e.g. total erupted mass) (ii) reduce the number of variables by eliminating non-influential parameters (e.g. particle density) and (iii) investigate the interactions among all input parameters (plume height, total grain-size distribution, diffusion coefficient, fall-time threshold and mass-distribution parameter). For the two test cases, we found that the total erupted mass significantly affects the model outputs and, therefore, it can be accurately estimated from field data of the fallout deposit, whereas the particle density can be fixed at its nominal value because it has negligible effects on the model predictions
    Description: Published
    Description: B06202
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: sensitivity analysis; uncertainty estimation; tephra dispersal models; Etna; Ruapehu. ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Detection of quarry and mine blast contamination in European regional catalogues (2010)
    Springer
    Details
    Publication Date: 2020-11-16
    Description: The presence of quarry and mine blasts in seismic catalogues is detected using the Wiemer and Baer (Bull Seism Soc Am 90(2):525–530, 2000) algorithm. The procedure is based on the observation that quarry blasts generally take place during daytime hours: the areas with a high ratio of daytime and night-time events are likely to be regions with quarry activity. In the first part of this work we have tested the method, using both a synthetic and a regional catalogue; in the second part the procedure has been applied to some of the European regional catalogues available on line. The comparison between the results obtained and the location of known quarries and mines for the analysed catalogues confirms the reliability of the methodology in identifying mining areas.
    Description: This research was partially supported by the transnational access activity of the European Union project NERIES (contract number 026130)
    Description: Published
    Description: 229–249
    Description: 4IT. Banche dati
    Description: JCR Journal
    Description: open
    Keywords: quarry blast; mine blast; seismic catalogue ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    Acoustic Emission spectra classification from rock samples of Etna basalt in deformation-decompression laboratory experiments (2011)
    Springer
    Details
    Publication Date: 2020-02-24
    Description: Recent laboratory experiments on Etna basalt have permitted the generation of an extensive catalogue of acoustic emissions (AE) during two key experimental phases. Firstly, AE have been generated during triaxial compressional tests and formation of a complex fracture/damage zone. Secondly, rapid fluid decompression through the damage/shear zone after failure. We report new results from an advanced analysis method using AE spectrograms, allowing us to qualitatively identify high and low frequency events; essentially comparable to seismicity in volcanic areas. Our analysis, for the first time, quantitatively classifies ‘families’ of AE events belonging to the same experimental stage without prior knowledge. We then test the method using the AE catalogue for verification, which is not possible with field data. FFT spectra, obtained from AE, are subdivided into equal log intervals for which a local slope is calculated. Factor analysis has been then applied, in which we use a data matrix of columns representing the variables considered (frequency data averaged in bins) vs. rows indicating each AE data set. Factor analysis shows that the method is very effective and suitable for reducing data complexity, allowing distinct factors to be obtained. We conclude that most of the data variance (information content) can be well represented by three factors only, each one representing a well defined frequency range. Through the factor scores it is possible to represent data in a lower dimension factor space. Classification is then possible by identifying clusters of AE belonging to the same experimental stage. This allows us to propose a deformation/decompression interpretation based solely on the AE frequency analysis and to identify a third type of AE related to fluid movements in the deformation stage.
    Description: Published
    Description: 201-211
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: open
    Keywords: acoustic emissions ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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