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Herber, Rolf; Grevemeyer, Ingo; Exner, O.; Villinger, Heinrich; Weigel, W.

doi:10.1023/a:1004552406168

Cited by 4 publications

(2 citation statements)

References 18 publications

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“…The initial implosion is most likely fast and can be associated with the radiation of high frequency waves up to 1,000 Hz as observed on hydrophones during the experiment (see Herber et al 1999). The dominant frequencies of possible air bubble oscillations may be much smaller.…”

Section: Characteristics Of the Implosive Sourcementioning

confidence: 83%

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Inversion of Scholte wave dispersion and waveform modeling for shallow structure of the Ninetyeast Ridge

2008

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The construction of S-wave velocity models of marine sediments down to hundreds of meters below the seafloor is important in a number of disciplines. One of the most significant trends in marine geophysics is to use interface waves to estimate shallow shear velocities which play an important role in determining the shallow crustal structure. In marine settings, the waves trapped near the fluid-solid interface are called Scholte waves, and this is the subject of the study. In 1998, there were experiments on the Ninetyeast Ridge (Central Indian Ocean) to study the shallow seismic structure at the drilled site. The data were acquired by both ocean bottom seismometer and ocean bottom hydrophone. A new type of seafloor implosion sources has been used in this experiment, which successfully excited fast and high frequency (>500 Hz) body waves and slow, intermediate frequency (<20 Hz) Scholte waves. The fundamental and first higher mode Scholte waves have both been excited by the implosion source. Here, the Scholte waves are investigated with a full waveform modeling and a group velocity inversion approach. Shear wave velocities for the uppermost layers of the region are inferred and results from the different methods are compared. We find that the full waveform modeling is important to understand the intrinsic attenuation of the Scholte waves between 1 and 20 Hz. The modeling shows that the S-wave velocity varies from 195 to 350 m/s in the first 16 m of the uppermost layer. Depths levels of high S-wave impedance contrasts compare well to the layer depth derived from a P-wave analysis as well as from drilling data. As expected, the P-to S-wave velocity ratio is very high in the uppermost 16 m of the seafloor and the Poisson ratio is nearly 0.5. Depth levels of high S-wave impedance contrasts are comparable to the layer depth derived from drilling data.

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Section: Characteristics Of the Implosive Sourcementioning

confidence: 83%

“…A technical description of the implosive source and its P-wave generation are given in Herber et al (1999). Here, we concentrate on the aspects of Scholte wave generation.…”

Section: Characteristics Of the Implosive Sourcementioning

confidence: 99%

Inversion of Scholte wave dispersion and waveform modeling for shallow structure of the Ninetyeast Ridge

2008

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Interaction of Underwater Blasts and Submerged Structures

Abrate

2012

Dynamic Failure of Composite and Sandwich Structures

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Full wavefield modeling and dispersion characteristics of underwater MASW

Tran,

Lin,

Pan

et al. 2024

Mar Geophys Res

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The underwater multichannel analysis of surface wave (UMASW) is becoming an essential tool for surveying subbottom shear wave velocity. Current practice is limited to interpretation based on the fundamental mode. This paper investigates the full dynamic response of the underwater-multilayered structure under two different types of sources (impact and explosion). Fundamental solutions in the transformed domain, after applying both Fourier transform and Fourier–Bessel transform, are derived utilizing the global stiffness matrix method, analogous to a 1-D finite element approach. Solutions in the physical domain are then obtained using the fast and accurate Fourier series and Fourier–Bessel series approach proposed in this paper. The most attractive feature of this novel approach is that the expansion coefficients (or Love numbers) can be pre-calculated, saved, and repeatedly used for other field points. Through numerical analyses, we quantitatively investigate the effect of the water depth and source/receiver types/locations on different wave features (i.e., Scholte, fast-guided, and acoustic modes) from different perspectives (i.e., dispersion curve, Green’s function, frequency-velocity spectrum (FVS), and waveform). We find that (1) unlike the impact source, stronger acoustic waves can be produced by the explosive source, which sometimes causes difficulty in identifying the Scholte waves. (2) The acoustic and interface-guided waves exhibit distinct behaviors depending on the source and receiver locations. Scholte waves and fast-guided waves are weakened when the source and receivers are elevated far from the water/soil interface. Moreover, (3) the response of the Scholte wave can be enhanced by muting the direct acoustic waves. However, (4) the fast-guided wave may also arise in underwater surveys when the Vs of the underlying half-space is much higher than those of the upper layers, exerting a significant influence on the shallow water scenarios and posing challenges for correct mode identification. With the ability to model the entire wavefield (or FVS) that takes into account all propagation modes and the actual survey configuration, inversion can be performed by fitting the entire FVS. This approach eliminates the need to pick dispersion curves and provides a more accurate and stronger model constraint.

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Cited by 4 publications

References 18 publications

Inversion of Scholte wave dispersion and waveform modeling for shallow structure of the Ninetyeast Ridge

Inversion of Scholte wave dispersion and waveform modeling for shallow structure of the Ninetyeast Ridge

Interaction of Underwater Blasts and Submerged Structures

Full wavefield modeling and dispersion characteristics of underwater MASW

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