Seismic on floating ice: data acquisition versus flexural wave noise

Johansen, Tor Arne; Ruud, Bent Ole; Tømmerbakke, R.; Jensen, Karl Kristoffer

doi:10.1111/1365-2478.12756

Cited by 4 publications

(7 citation statements)

References 34 publications

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“…5 illustrates that since the air-coupled flexural wave precedes the arrival of the air wave, it is recorded equally well for both point and line sources. This is significant because much of our field data employed line sources in order to attenuate the trailing lowfrequency ice flexural waves that are an unwanted noise component from the perspective of reflection seismic surveying (Johansen et al, 2019).…”

Section: Resultsmentioning

confidence: 99%

“…The main purpose of these experiments was to test different acquisition designs for reflection seismic surveying of sub-seabed sediments, as reported by Johansen et al (2019), an objective which is made difficult by the flexural wave energy propagating through the ice. Various source and receiver arrangements were tested including airguns, hydrophones and ocean bottom seismometers.…”

Section: Study Area and Data Acquisitionmentioning

confidence: 99%

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Sea ice thickness from air-coupled flexural waves

et al. 2021

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Abstract. Air-coupled flexural waves (ACFWs) appear as wave trains of constant frequency that arrive in advance of the direct air wave from an impulsive source travelling over a floating ice sheet. The frequency of these waves varies with the flexural stiffness of the ice sheet, which is controlled by a combination of thickness and elastic properties. We develop a theoretical framework to understand these waves, utilizing modern numerical and Fourier methods to give a simpler and more accessible description than the pioneering yet unwieldy analytical efforts of the 1950s. Our favoured dynamical model can be understood in terms of linear filter theory and is closely related to models used to describe the flexural waves produced by moving vehicles on floating plates. We find that air-coupled flexural waves are a real and measurable component of the total wave field of floating ice sheets excited by impulsive sources, and we present a simple closed-form estimator for the ice thickness based on observable properties of the air-coupled flexural waves. Our study is focused on first-year sea ice of ∼ 20–80 cm thickness in Van Mijenfjorden, Svalbard, that was investigated through active source seismic experiments over four field campaigns in 2013, 2016, 2017 and 2018. The air-coupled flexural wave for the sea ice system considered in this study occurs at a constant frequency thickness product of ∼ 48 Hz m. Our field data include ice ranging from ∼ 20–80 cm thickness with corresponding air-coupled flexural frequencies from 240 Hz for the thinnest ice to 60 Hz for the thickest ice. While air-coupled flexural waves for thick sea ice have received little attention, the readily audible, higher frequencies associated with thin ice on freshwater lakes and rivers are well known to the ice-skating community and have been reported in popular media. The results of this study and further examples from lake ice suggest the possibility of non-contact estimation of ice thickness using simple, inexpensive microphones located above the ice sheet or along the shoreline. While we have demonstrated the use of air-coupled flexural waves for ice thickness monitoring using an active source acquisition scheme, naturally forming cracks in the ice are also shown as a potential impulsive source that could allow passive recording of air-coupled flexural waves.

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Section: Resultsmentioning

confidence: 99%

Section: Study Area and Data Acquisitionmentioning

confidence: 99%

Sea ice thickness from air-coupled flexural waves

et al. 2021

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“…The vertical particle velocity in water can be computed from the pressure (Johansen et al . ) as

V_{z} = {(i ω ρ)}^{- 1} \frac{\partial P}{\partial z}

. This gives

V_{z} = \frac{ξ}{ρ} A_{d} [\exp (i ω ξ z) + \exp (- i ω ξ z)] normalexp [i ω (p x - t)]

and for Scholte waves with

p ≫ 1 / V_{w}

, we get

V_{z} = \frac{i p}{ρ} A_{d} [\exp (- ω p z) + \exp (ω p z)] normalexp [i ω (p x - t)] .

…”

Section: Scholte Wave Data Acquired On Shallow Watermentioning

confidence: 89%

“…Further details about the seismic experiments and the recording equipment can be found in Johansen et al . (2019a,b). The instrument responses were all similar to that of analogue geophones, but with a natural frequency, which varied between the different types of sensors.…”

Section: Scholte Wave Data Acquired On Shallow Watermentioning

confidence: 99%

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Characterization of seabed properties from Scholte waves acquired on floating ice on shallow water

Johansen

Ruud

2020

Near Surface Geophysics

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A B S T R A C TSeismic surveying of the coastal areas in the Arctic is best facilitated during wintertime when the sea ice is land-fast. This eases the logistics of the operation and assures that there is no damage made to the vulnerable tundra. Seismic experiments on floating ice on shallow water performed in a fjord in Svalbard in the Norwegian Arctic show prominent Scholte waves. The dispersion relation of Scholte waves can provide the shear wave velocities of the seabed sediments. Scholte wave data can potentially be obtained when the seismic source and geophone receivers are both placed on top of the floating ice. However, the Scholte wave data become more distinct by using an air gun lowered some metres below the ice. A rock physics model based on a twostep differential effective medium scheme has been tuned to predict seismic properties found for very loose sediments, among these very high P-wave to S-wave velocity ratios. The rock physics model enables us to convert seismic velocities obtained from Scholte wave data to quantitative estimates of the sediment composition.

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Arctic-Type Seismoacoustic Waveguide: Theoretical Foundations and Experimental Results

Sobisevich,

Presnov,

Shurup

2024

JMSE

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The results of theoretical analysis and practical implementation of seismoacoustic methods developed for monitoring ice-covered regions in the Arctic are presented and discussed. Special attention is paid to passive seismoacoustic tomography as a unique method of studying the deep structure of the lithosphere and hydrosphere without the use of powerful sources. One of the distinctive features of the considered approach is the use of receivers located on the ice surface to recover characteristics of Arctic-type seismoacoustic waveguide “lithosphere-hydrosphere-ice cover”. In passive monitoring, special attention is paid to reducing the noise signal accumulation time required to obtain seismoacoustic wave propagation times, as well as expanding the analyzed frequency bandwidth. The presented results can be used to develop technologies for seasonal and long-term monitoring of the currently observed variability of large areas of the Arctic region due to climatic changes.

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Seismic on floating ice: data acquisition versus flexural wave noise

Cited by 4 publications

References 34 publications

Sea ice thickness from air-coupled flexural waves

Sea ice thickness from air-coupled flexural waves

Characterization of seabed properties from Scholte waves acquired on floating ice on shallow water

Arctic-Type Seismoacoustic Waveguide: Theoretical Foundations and Experimental Results

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