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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 114 (1993), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In traveltime tomography, Vp/Vs models calculated as ratio between the resolved P and S models are affected by the different ray coverages and phase-onset reading accuracies of P and S waves. the result of this is that the computed Vp/Vs models can display large fluctuations which are unrelated to the true structure. Introduction of some P-S coupling (e.g. proportionality, correlation) as a priori data permits us to stabilize the resulting Vp/Vs model about a preselected average value and to minimize the insurgence of fictitious Vp/Vs anomalies. In general, addition of P-S coupling trades off with data misfit and adoption of this technique is suggested for robustness tests of resolved Vp/Vs features. the technique is applied to a synthetic data set generated using an idealized fault structure and the source-receiver geometry existing at Parkfield, California.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 121 (1995), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The use of an adaptive-grid formalism for seismic, non-linear traveltime tomography is proposed. The method is based on a parametric representation of the velocity model and involves the simultaneous inversion for both velocity and position of the grid points of the model discretization mesh. Therefore, the method seeks the optimal grid configuration to define the model. Cubic B-spline basis functions have been used for model representation as they are particularly versatile in the reproduction of geologically complex structures. The traveltimes are calculated using a new initial-value ray tracer that calculates the ray trajectories directly in the parametric domain.The method is tested against synthetic data generated for various cross-hole geometries. It is found that, in parts of the model having good ray coverage, the method accurately retrieves velocity anomalies of arbitrary shape using a generally small number of grid points of the inversion discretization mesh. With the exception of initial meshes that are too coarse to describe accurately the complexity of the true structure, the method retrieves nearly identical final models regardless of the predefined node spacing and node configuration. Therefore, the method can avoid very fine discretization, and matrix sparseness, one of the main sources of indeterminacy, is similarly avoided. When compared with standard methods entailing a similar total number of inversion parameters, our results show the pitfalls that may derive from the a priori assigning of a fixed-grid mesh. Overall, the parametric representation leads to some saving in the total number of inversion parameters when the structure consists of sparse distributions of irregular features. Other styles of model may be better recovered by regular grids for a given number of inversion parameters.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 115 (1993), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The use of parametric curves to define velocity models in seismic traveltime tomography is proposed. This approach provides increased flexibility in shaping the velocity models because it allows inversion for both velocity and grid point adjustments. The method is applied to a data set generated from a 1-D profile having sharp discontinuities. The results are compared with those obtained from other methods currently in use for traveltime tomography. It is found that large gradients and discontinuities can be retrieved with improved accuracy and that instabilities caused by non-optimal prior selection of the inversion grid can be avoided. The results appear to be robust when the sizes of both data and model space are reduced which makes the method appealing for the solution of large-scale tomographic problems.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2012-12-01
    Print ISSN: 0920-4105
    Electronic ISSN: 1873-4715
    Topics: Chemistry and Pharmacology , Geosciences , Process Engineering, Biotechnology, Nutrition Technology
    Published by Elsevier
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  • 5
    Publication Date: 2015-09-01
    Print ISSN: 0920-4105
    Electronic ISSN: 1873-4715
    Topics: Chemistry and Pharmacology , Geosciences , Process Engineering, Biotechnology, Nutrition Technology
    Published by Elsevier
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  • 6
    Publication Date: 2016-11-09
    Description: The Istituto Nazionale di Geofisica e Vulcanologia (INGV) is an Italian research institution, with focus on Earth Sciences. INGV runs the Italian National Seismic Network (Rete Sismica Nazionale, RSN) and other networks at national scale for monitoring earthquakes and tsunami as a part of the National Civil Protection System coordinated by the Italian Department of Civil Protection (Dipartimento di Protezione Civile, DPC). RSN is composed of about 400 stations, mainly broadband, installed in the Country and in the surrounding regions; about 110 stations feature also co-located strong motion instruments, and about 180 have GPS receivers and belong to the National GPS network (Rete Integrata Nazionale GPS, RING). The data acquisition system was designed to accomplish, in near-real-time, automatic earthquake detection, hypocenter and magnitude determination, moment tensors, shake maps and other products of interest for DPC. Database archiving of all parametric results are closely linked to the existing procedures of the INGV seismic monitoring environment and surveillance procedures. INGV is one of the primary nodes of ORFEUS (Observatories & Research Facilities for European Seismology) EIDA (European Integrated Data Archive) for the archiving and distribution of continuous, quality checked seismic data. The strong motion network data are archived and distributed both in EIDA and in event based archives; GPS data, from the RING network are also archived, analyzed and distributed at INGV. Overall, the Italian earthquake surveillance service provides, in quasi real-time, hypocenter parameters to the DPC. These are then revised routinely by the analysts of the Italian Seismic Bulletin (Bollettino Sismico Italiano, BSI). The results are published on the web, these are available to both the scientific community and the general public. The INGV surveillance includes a pre-operational tsunami alert service since INGV is one of the Tsunami Service providers of the North-eastern Atlantic and Mediterranean Tsunami warning System (NEAMTWS).
    Print ISSN: 1680-7340
    Electronic ISSN: 1680-7359
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
    Publication Date: 2021-05-12
    Description: eological storage is one of the solutions to avoid the emission of carbon dioxide to the atmosphere. This process requires a careful monitoring of the CO2 bubble, which can be performed by means of seismic and electromagnetic (EM) methods, on the basis of seismic velocity, attenuation and electrical conductivity contrasts before and after the injection. A successful monitoring depends on many factors, for instance the depth and properties of the reservoir. To test the feasibility of detecting the gas, we have performed cross-well seismic and EM tomographic inversions on a synthetic data set generated from a realistic aquifer partially saturated with CO2. We use two different algorithms based on traveltime picks. The method is novel regarding the EM inversion. Besides seismic velocity and conductivity, we have also obtained the seismic quality factor by performing attenuation tomography based on the frequency-shift approach. The RMS differences between the inverted and true initial models show that the methodology (and the adopted acquisition geometry) allows us to obtain reliable results which agree well with the true petrophysical model. Moreover, we have used a forward optimisation method to recover saturation, porosity and clay content from the tomographic seismic velocities, Q values and electric conductivity, with errors less than 15%
    Description: Published
    Description: 245-257
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
    Publication Date: 2018-03-12
    Description: The Istituto Nazionale di Geofisica e Vulcanologia runs the Italian National Seismic Network (about 400 stations, seismometers, accelerometers and GPS antennas) and other networks at national scale for monitoring earthquakes and tsunami as a part of the National Civil Protection System coordinated by the Italian Department of Civil Protection. This work summarises the acquisition and the distribution of the data and the analysis that are carried out for seismic surveillance and tsunami alert.
    Description: INGV and DPC
    Description: Published
    Description: 31-38
    Description: 1IT. Reti di monitoraggio
    Description: N/A or not JCR
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
    Publication Date: 2021-12-23
    Description: Machine learning is becoming increasingly important in scientific and technological progress, due to its ability to create models that describe complex data and generalize well. The wealth of publicly-available seismic data nowadays requires automated, fast, and reliable tools to carry out a multitude of tasks, such as the detection of small, local earthquakes in areas characterized by sparsity of receivers. A similar application of machine learning, however, should be built on a large amount of labeled seismograms, which is neither immediate to obtain nor to compile. In this study we present a large dataset of seismograms recorded along the vertical, north, and east components of 1487 broad-band or very broad-band receivers distributed worldwide; this includes 629,095 3-component seismograms generated by 304,878 local earthquakes and labeled as EQ, and 615,847 ones labeled as noise (AN). Application of machine learning to this dataset shows that a simple Convolutional Neural Network of 67,939 parameters allows discriminating between earthquakes and noise single-station recordings, even if applied in regions not represented in the training set. Achieving an accuracy of 96.7, 95.3, and 93.2% on training, validation, and test set, respectively, we prove that the large variety of geological and tectonic settings covered by our data supports the generalization capabilities of the algorithm, and makes it applicable to real-time detection of local events. We make the database publicly available, intending to provide the seismological and broader scientific community with a benchmark for time-series to be used as a testing ground in signal processing.
    Description: Published
    Description: 1-10
    Description: 1SR TERREMOTI - Sorveglianza Sismica e Allerta Tsunami
    Description: N/A or not JCR
    Keywords: Physics - Geophysics; Physics - Geophysics ; dataset for machine learning in seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
    Publication Date: 2021-12-14
    Description: The Italian earthquake waveform data are collected here in a dataset suited for machine learning analysis (ML) applications. The dataset consists of nearly 1.2 million three-component (3C) waveform traces from about 50 000 earthquakes and more than 130 000 noise 3C waveform traces, for a total of about 43 000 h of data and an average of 21 3C traces provided per event. The earthquake list is based on the Italian Seismic Bulletin (http://terremoti.ingv.it/bsi, last access: 15 February 2020​​​​​​​) of the Istituto Nazionale di Geofisica e Vulcanologia between January 2005 and January 2020, and it includes events in the magnitude range between 0.0 and 6.5. The waveform data have been recorded primarily by the Italian National Seismic Network (network code IV) and include both weak- (HH, EH channels) and strong-motion (HN channels) recordings. All the waveform traces have a length of 120 s, are sampled at 100 Hz, and are provided both in counts and ground motion physical units after deconvolution of the instrument transfer functions. The waveform dataset is accompanied by metadata consisting of more than 100 parameters providing comprehensive information on the earthquake source, the recording stations, the trace features, and other derived quantities. This rich set of metadata allows the users to target the data selection for their own purposes. Much of these metadata can be used as labels in ML analysis or for other studies. The dataset, assembled in HDF5 format, is available at http://doi.org/10.13127/instance (Michelini et al., 2021).
    Description: Published
    Description: 5509–5544
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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