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    Publication Date: 2022-02-11
    Description: We present Rapid Assessment of MOmeNt and Energy Service (RAMONES), a service for disseminating through a web interface, the estimates of seismic moment (⁠M0⁠) and radiated energy (⁠ER⁠) for earthquakes occurring in central Italy with local magnitudes above 1.7. The service is based on a fully‐automatic procedure developed for downloading and processing open seismological data from the European Integrated Data Archive, Italian Civil Protection repository, and Incorporated Research Institutions for Seismology (IRIS). In its actual configuration, RAMONES uses the seismic catalog generated through the event webservice of the Italian Institute of Geophysics and Volcanology (compliant with International Federation of Digital Seismograph Networks standards) to guide the data download. The concept of RAMONES is to estimate M0 and ER from features extracted directly from recordings, namely the S‐wave peak displacement (⁠PDS⁠) and the integral of the squared velocity (⁠IV2S⁠) evaluated over the S‐wave window at local distances. A data set composed of 6515 earthquakes recorded in central Italy between 2008 and 2018 was used to calibrate the attenuation models relating M0 to PDS and ER to IV2S⁠, including station corrections. The calibration values for M0 and ER were extracted from the source spectra obtained by applying a decomposition approach to the Fourier amplitude spectra known as the generalized inversion technique. To test the capabilities of RAMONES, we validate the attenuation models by performing residual analysis over about 60 earthquakes occurring in 2019 that were used for the spectral decomposition analysis but not considered in the calibration phase. Since January 2020, a testing operational phase has been running, and RAMONES has analyzed about 800 earthquakes by September 2020. The distribution of the source parameters and their relevant scaling relationships are automatically computed and disseminated in the form of maps, parametric tables, figures, and reports available through the RAMONES web interface.
    Description: Published
    Description: 1759–1772
    Description: 3T. Fisica dei terremoti e Sorgente Sismica
    Description: JCR Journal
    Keywords: source parameters, coda waves, radiated energy, moment magnitude, corner frequency ; source parameters
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2023-11-16
    Description: We apply a spectral decomposition approach to isolate the source spectra from propagation and site effects and, in turn, to estimate the source parameters of small‐to‐moderate earthquakes that occurred in central Italy. The data set is composed of about 400,000 waveforms relevant to 4111 earthquakes in the moment magnitude range 1.5–6.5, recorded by a high‐density network of stations installed in the study area. We first investigate the reliability of the source parameters for small magnitudes through numerical simulations. We generate synthetic spectra for different source scaling models and near‐surface attenuation effects, considering the source–station geometry and the data availability of the central Italy data set. Our analysis with synthetics shows that the spectral decomposition is effective in isolating the source contributions from other factors. Moreover, the analysis of the residual distributions suggests that moment magnitude 1.8 is the lower bound for the retrieval of reliable Brune’s source parameters, although we observe an increase of residual’s variability below magnitude 3, and the estimated source parameters could be biased below magnitude 2.3. Remarkably, the assessment of the stress drop Δσ for small events is strongly hampered by site‐specific attenuation near the surface. In view of the results with synthetics, we analyze the source parameters of earthquakes recorded in central Italy. The corner frequency versus seismic moment relationship describes a source scaling in which Δσ increases with increasing moment magnitude Mw⁠, the mean Δσ varying from 0.1 MPa for Mw〈2 to 7.9 MPa for Mw〉5⁠. In particular, Δσ increases mainly for Mw in the ranges 2.5–3 and 4.5–5.2. The corner frequencies estimated from the apparent source spectra do not show any dependence on hypocentral distance and magnitude, confirming that uncorrected anelastic attenuation effects do not significantly bias the results.
    Description: Published
    Description: 3139–3157
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: source parameters ; Central Italy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2023-01-31
    Description: Deep fluids play active roles during the preparatory phases of large earthquakes and, through their chemical signature, carry information about deep processes within the seismogenic crust. Due to its inertness and isotopic signature, helium (the lightest noble gas) is a useful tracer for investigating the processes of storage and transfer of fluids through the crust, including those prior to hazardous earthquakes. Here we analyse a 12-year earthquake catalogue from the Irpinia Fault Zone, Italy, to compute the 4He outputs from the seismogenetic fault zones (from 104 to 106 mol y−1 with an annual tenfold variability) and compare these with estimates of long-term helium flux. We find that low-magnitude earthquakes (M 〈 4) efficiently contribute to variations of the crustal helium output into the atmosphere which supports the impulsive nature of He degassing in tectonically active continental regions. We conclude that there is a quantitative relationship between crustal helium outputs and the volume of fault zones, and suggest variations in helium flux may represent a gauge of changes in the stress field that are related to the nucleation of earthquakes.
    Description: Published
    Description: 224
    Description: 9T. Geochimica dei fluidi applicata allo studio e al monitoraggio di aree sismiche
    Description: JCR Journal
    Keywords: helium ; earth degassing ; earthquakes ; Near fault observatory
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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