2025_programme: Analysis of passive distributed acoustic sensing data for observation of microseisms and extracting Scholte wave dispersion in shallow water

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  • Day: June 20, Friday
      Location / Time: A. TERPSIHORI at 08:30 - 08:50
  • Last minutes changes: -
  • Session: 05. Distributed Fiber-Optic Sensing technology for underwater acoustical monitoring
    Organiser(s): Alexander Gavrilov, Evgenii Sidenko, Hefeng Dong
    Chairperson(s): Hefeng Dong, Evgenii Sidenko
  • Lecture: Analysis of passive distributed acoustic sensing data for observation of microseisms and extracting Scholte wave dispersion in shallow water
    Paper ID: 2110
    Author(s): Hefeng Dong, Michael Taroudakis
    Presenter: Hefeng Dong
    Abstract: In recent years, the emerging technology of Distributed Acoustic Sensing (DAS), measuring the strain in a fiber-optic (FO) cable caused by acoustic waves, has been used for monitoring and imaging of trains, pipelines, earthquakes, whale and oil fields, etc. DAS systems have the advantage over traditional receiving systems since it can provide densely sampled array along the FO cable and wide-band signals, especially low frequency response. In this study, the Tampnet DAS dataset released from “The Global DAS Month of February 2023, https://doi.org/10.1785/0220230180” is chosen. This dataset was collected by an OptoDAS interrogator from ASN on an 80-km FO telecom cable on the seafloor in shallow water of the Southern North Sea. The dataset is not entirely continuous in time but contains patches of continuous data. A patch of two-hour continuous strain signal is studied. The ambient noise is dominated by periodic shoaling ocean surface waves, but also contains interaction of ocean wind-waves. Thanks to the good low-frequency response of DAS system, both primary and secondary microseisms are observed by frequency-wavenumber analysis. The primary microseisms are generated by the ocean surface gravity wave interaction with seafloor with two asymmetric dispersive waves which agree well with the theoretical linear gravity dispersion curves in shallow water (30 - 45 m). The secondary microseisms are caused by the interaction of ocean wind-waves propagating in opposite directions and are characterized by Scholte waves travelling outward with equal energy at near acoustic speeds between 200 - 1000 m/s. Greens’ functions are retrieved by applying passive seismic interferometry to the two-hour continuous strain data, which contains Scholte wave. The image of Scholte wave dispersion is extracted using time-frequency analysis. The shear-wave speeds of the upper sediment layers can be estimated by inverting the dispersion curve of the Scholte wave in a nonlinear geoacoustic inversion.
      Download the full paper
  • Corresponding author: Dr Hefeng Dong
    Affiliation: Norwegian University of Science and Technology, NTNU
    Country: Norway

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