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  • Seismological Society of America (SSA)
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    Seismological Society of America (SSA)
    In:  EPIC3The Seismic Record, Seismological Society of America (SSA), 3(2), pp. 125-133, ISSN: 2694-4006
    Publication Date: 2024-03-14
    Description: We present distributed fiber-optic sensing data from an airplane landing near the EastGRIP ice core drilling site on the Northeast Greenland Ice Stream. The recordings of exceptional clarity contain at least 15 easily visible wave propagation modes corresponding to various Rayleigh, pseudoacoustic, and leaky waves. In the frequency range from 8 to 55 Hz, seven of the modes can be identified unambiguously. Based on an a priori firn and ice model that matches P-wave dispersion and the fundamental Rayleigh mode, a Backus–Gilbert inversion yields an S-wavespeed model with resolution lengths as low as a few meters and uncertainties in the range of only 10 m/s. An empirical scaling from S wavespeed to density leads to a depth estimate of the firn–ice transition between 65 and 71 m, in agreement with direct firn core measurements. This work underlines the potential of distributed fiber-optic sensing combined with strong unconventional seismic sources in studies of firn and ice properties, which are critical ingredients of ice core cli-matology, as well as ice sheet dynamics and mass balance calculations.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 2
    Publication Date: 2024-04-30
    Description: This study presents data and preliminary analysis from a temporary seismic network (SPQR), which was deployed in the urban area of Rome (Italy) for three months in early 2021. The network was designed to investigate the city’s subsurface while evaluating the feasibility of a permanent urban seismic network, and consisted of 24 seismic stations. Despite significant anthropogenic noise, the SPQR network well recorded earthquake signals, revealing clear spatial variability referable to site effects. In addition, the network’s continuous recordings allowed the use of seismic noise and earthquake signals to derive spectral ratios at sites located in different geological and lithological settings. During the experiment, there were periods of activity restrictions imposed on citizens to limit the spread of COVID‐19. Although the observed power spectral density levels at stations may not show visible noise reductions, they do cause variations in calculated spectral ratios across measurement sites. Finally, a statistical noise analysis was conducted on continuous seismic station data to evaluate their performance in terms of detection threshold for earthquakes. The results indicate that all network stations can effectively record earthquakes with a good signal‐to‐noise ratio (≥5 for P and S phases) in the magnitude range of 1.9–3.3 at distances of 10 km and 80 km, respectively. In addition, the network has the potential to record earthquakes of magnitude 4 up to 200 km, covering areas in Central Italy that are far from the city. This analysis shows that it is possible to establish urban observatories in noisy cities such as Rome, where hazard studies are of particular importance due to the high vulnerability (inherent fragility of its monumental heritage) and exposure.
    Description: The experiment was financed with funds of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) dedicated to the institution’s open research projects (RicercaLibera) to promote free research within the INGV (Research Project: Three-dimensional shear-wave velocity imaging by ambient seismic noise tomography in the urban area of Rome city - Central Italy)
    Description: In press
    Description: OST5 Verso un nuovo Monitoraggio
    Description: JCR Journal
    Keywords: Urban seismology ; Seismic Site Effect ; Detection threshold of seismic network ; Seismic noise ; 04.06. Seismology ; 04.04. Geology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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