Long-range correlations of microseism-band pressure fluctuations in the ocean

Ball, Justin S.; Godin, Oleg A.; Evers, Läslo; Lv, Cheng Xing

doi:10.1093/gji/ggw110

Cited by 6 publications

(3 citation statements)

References 46 publications

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“…showed how temperature variations at H10 can be retrieved from the ambient noise field on a monthly basis. Recently, Scholte waves were identified by applying interferometry to the H10 hydroacoustic data in the microseism-band, that is, around 0.2 Hz (Ball et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Deep ocean sound speed characteristics passively derived from the ambient acoustic noise field

Evers

Wapenaar

Heaney

et al. 2017

Geophysical Journal International

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S U M M A R YThe propagation of acoustic waves in the ocean strongly depends on the temperature. Lowfrequency acoustic waves can penetrate the ocean down to depths where few in situ measurements are available. It is therefore attractive to obtain a measure of the deep ocean temperature from acoustic waves. The latter is especially true if the ambient acoustic noise field can be used instead of deterministic transient signals. In this study the acoustic velocity, and hence the temperature, is derived in an interferometric approach from hydrophone array recordings. The arrays were separated by over 125 km, near Ascension Island in the Atlantic Ocean, at a depth of 850 m. Furthermore, the dispersive characteristics of the deep ocean sound channel are resolved based on the retrieved lag times for different modes. In addition, it is shown how the resolution of the interferometric approach can be increased by cross correlating array beams rather than recordings from single-sensor pairs. The observed acoustic lag times between the arrays corresponds well to modelled values, based on full-wave modelling through best-known oceanic models.

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Section: Introductionmentioning

confidence: 99%

Deep ocean sound speed characteristics passively derived from the ambient acoustic noise field

Evers

Wapenaar

Heaney

et al. 2017

Geophysical Journal International

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“…Most notable is the correlation of the highest energy levels with microseism peaks (0.1 Hz and 0.16–0.3 Hz, respectively) due to surface wind wave interaction (Longuet-Higgins 1950 ; Hasselmann 1963 ; Babcock et al 1994 ). Using cross-correlation of noise spectra in the microseism band (0.1–1 Hz) from the Atlantic, Ball et al ( 2016 ) identify temporal amplitude variations within a year and dominant source regions associated with the main microseismic excitation mechanisms and sources.…”

Section: Hydroacoustic Sourcesmentioning

confidence: 99%

Natural and Anthropogenic Sources of Seismic, Hydroacoustic, and Infrasonic Waves: Waveforms and Spectral Characteristics (and Their Applicability for Sensor Calibration)

et al. 2022

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The record of seismic, hydroacoustic, and infrasonic waves is essential to detect, identify, and localize sources of both natural and anthropogenic origin. To guarantee traceability and inter-station comparability, as well as an estimation of the measurement uncertainties leading to a better monitoring of natural disasters and environmental aspects, suitable measurement standards and reliable calibration procedures of sensors, especially in the low-frequency range down to 0.01 Hz, are required. Most of all with regard to the design goal of the Comprehensive Nuclear-Test-Ban Treaty Organisation’s International Monitoring System, which requires the stations to be operational nearly 100% of the time, the on-site calibration during operation is of special importance. The purpose of this paper is to identify suitable excitation sources and elaborate necessary requirements for on-site calibrations. We give an extensive literature review of a large variety of anthropogenic and natural sources of seismic, hydroacoustic, and infrasonic waves, describe their most prominent features regarding signal and spectral characteristics, explicitly highlight some source examples, and evaluate the reviewed sources with respect to requirements for on-site calibrations such as frequency bandwidth, signal properties as well as the applicability in terms of cost–benefit. According to our assessment, earthquakes stand out across all three waveform technologies as a good natural excitation signal meeting the majority of the requirements. Furthermore, microseisms and microbaroms allow a calibration at very low frequencies. We also find that in each waveform technique man-made controlled sources such as drop weights or air guns are in good agreement with the required properties, although limitations may arise regarding the practicability. Using these sources, procedures will be established allowing calibration without record interrupting, thereby improving data quality and the identification of treaty-related events.

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“…As noticed by Ball et al (2016), an analytical solution exists for the dispersion relation 1, but its numerical solution is much easier to calculate. When wavenumbers K of all modes existing in the frequency domain of interest are known, the group speed of each mode can be easily deduced.…”

Section: A Numerical Resolution Of the Dispersion Relationmentioning

confidence: 99%

Numerical modeling and observations of seismo-acoustic waves propagating as modes in a fluid-solid waveguide

Lecoulant¹,

Guennou²,

Guillon

et al. 2022

The Journal of the Acoustical Society of America

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This paper discusses the nature of the low-frequency seismo-acoustic waves generated by submarine earthquakes in the ocean. In a finite-depth homogeneous ocean over a semi-infinite solid crust, the derivation of the acoustic equations shows that waves propagate as modes. The waves propagating with the speed of sound in water (T waves) are preceded by waves with frequencies below the Airy phase. Furthermore, the group speeds of these modes are sensitive to the environmental setting. As a test, we applied the spectral finite-element code SPECFEM2D in a simplified configuration with an ocean layer overlaying a solid crust, and a seismic source below a Gaussian seamount surrounded by a flat seafloor. The simulations confirm that the generated T waves and their precursors follow the theoretical dispersion curves. A more realistic environment with a seismically-layered crust and a sound-speed profile in the ocean is then used to predict the expected acoustic modes. Although noisy, recordings by ocean bottom seismometers from the southwest Indian Ocean show T waves preceded by ultra-low frequency waves, which display two modes comparable to the theoretical ones. They are in good agreement for mode 1, whereas, for mode 0, a slight offset in frequency has yet to be explained.

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Long-range correlations of microseism-band pressure fluctuations in the ocean

Cited by 6 publications

References 46 publications

Deep ocean sound speed characteristics passively derived from the ambient acoustic noise field

Deep ocean sound speed characteristics passively derived from the ambient acoustic noise field

Natural and Anthropogenic Sources of Seismic, Hydroacoustic, and Infrasonic Waves: Waveforms and Spectral Characteristics (and Their Applicability for Sensor Calibration)

Numerical modeling and observations of seismo-acoustic waves propagating as modes in a fluid-solid waveguide

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