The signature of an air gun array: Computation from near‐field measurements including interactions

Ziolkowski, Anton; Parkes, Gregg; Hatton, Les; Haugland, T.

doi:10.1190/1.1441289

Cited by 248 publications

(163 citation statements)

References 9 publications

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“…The source was positioned at approximately 3,5,7,10,15,20,25,30,35, and 40 m, and a hydrophone was positioned 20 m below the source. The far-field signatures for sources fired at different depths were estimated by the notional source method (Ziolkowski et al, 1982) and then convolved with the source ghost functions for the respective source depths. The data were filtered with a high-cut filter (230-250 Hz) and normalized to the highest amplitude.…”

Section: Optimal Source Depths Using Field Datamentioning

confidence: 99%

Variable source depth acquisition for improved marine broadband seismic data

Haavik¹,

Landrø²

2015

GEOPHYSICS

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In marine seismic data acquisition, varying the source depth along a sail line gives diversity in sequential shot gather frequency spectra. Undesired alterations of the frequency spectra are created by the source ghost and by air-gun bubble oscillations. By deliberately varying the source depth along a sail line, it is possible to obtain a seismic data set that will have energy more evenly distributed within the main frequency band of the source output. This is obtained when data acquired with different source depths are stacked in imaging. We formulated a simple inverse problem that seeks to find the optimal distribution of source depths over a sequential series of shots that shape the amplitude spectrum of the final image into a desired shape. We assumed that the data are receiver-side deghosted, that designature could be applied to each shot gather, and that the shot gathers could be redatumed to a common datum prior to imaging.

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Section: Optimal Source Depths Using Field Datamentioning

confidence: 99%

Variable source depth acquisition for improved marine broadband seismic data

Haavik¹,

Landrø²

2015

GEOPHYSICS

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“…This indicates that the simple tapering process might not be good enough to generate the pure first arrivals. An appropriate treatment could be a global debubbling operation (Ziolkowski et al, 1980(Ziolkowski et al, , 1982 with respect to all the VSP downgoing waveforms because this would help to clean up the waveform before muting. …”

Section: D222 Wangmentioning

confidence: 99%

Stable Q analysis on vertical seismic profiling data

Wang

2014

GEOPHYSICS

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Vertical seismic profiling (VSP) provides a direct observation of seismic waveforms propagating to various depths within the earth's subsurface. The Q analysis or attenuation (1∕Q) analysis based on direct comparison between individual waveforms at different depths, however, suffers from the problem of instability commonly due to fluctuations inherent in the frequency spectrum of each waveform. To improve the stability, we considered frequency and time variations and conducted Q analysis on an integrated observation. First, we transformed the time-(or depth-) frequency-domain spectrum to a 1D attenuation measurement with respect to a single variable, the product of time and frequency. Although this 1D measurement has a higher signal-to-noise ratio than the 2D spectrum in the time-frequency domain, it can also be used to further generate a stabilized compensation function. Then, we implemented two Q-analysis methods by data fitting (in a least-squares sense) to either the attenuation measurement or the data-driven gain function. These two methods are theoretically consistent and practically robust for conducting Q analysis on field VSP data.

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“…This variability makes airgun array signature modeling complex and difficult. One can estimate the signature from near-field measurements of an airgun array (Ziolkowski et al, 1982(Ziolkowski et al, , 1997Laws et al, 1998), but during the CEEs we studied, no near-field measurements of airgun pulses were made. An alternative way to estimate the signature of an airgun array is to treat each element as a monopole source and consider the geometric configuration of the array.…”

Section: Alrgun Array Beampattern Modelmentioning

confidence: 99%

Echolocation-based foraging by harbor porpoises and sperm whales, including effects of noise and acoustic propagation

DeRuiter¹

2008

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In this thesis, I provide quantitative descriptions of toothed whale echolocation and foraging behavior, including assessment of the effects of noise on foraging behavior and the potential influence of ocean acoustic propagation conditions on biosonar detection ranges and whale noise exposure. In addition to presenting some novel basic science findings, the case studies presented in this thesis have implications for future work and for management.In Chapter 2, I describe the application of a modified version of the Dtag to studies of harbor porpoise echolocation behavior. The study results indicate how porpoises vary the rate and level of their echolocation clicks during prey capture events; detail the differences in echolocation behavior between different animals and in response to differences in prey fish; and show that, unlike bats, porpoises continue their echolocation buzz after the moment of prey capture.Chapters 3-4 provide case studies that emphasize the importance of applying realistic models of ocean acoustic propagation in marine mammal studies. These chapters illustrate that, although using geometric spreading approximations to predict communication/target detection ranges or noise exposure levels is appropriate in some cases, it can result in large errors in other cases, particularly in situations where refraction in the water column or multi-path acoustic propagation are significant.Finally, in Chapter 5, I describe two methods for statistical analysis of whale behavior data, the rotation test and a semi-Markov chain model. I apply those methods to test for changes in sperm whale foraging behavior in response to airgun noise exposure. Test results indicate that, despite the low-level exposures experienced by the whales in the study, some (but not all) of them reduced their buzz production rates and altered other foraging behavior parameters in response to the airgun exposure. Sincere thanks also to the many other people who have helped with data collection and analysis over the course of my graduate work, and also to everyone who offered comments on drafts of this thesis. More detailed acknowledgments can be found at the end of each chapter, but here I would especially like to thank the following. Thesis Objectives and Chapter 1 OverviewThe goal of my thesis research has been to provide quantitative descriptions of toothed whale echolocation and foraging behavior (Chapters 2 and 5), including assessment of the effects of noise on foraging behavior (Chapter 5) and the potential influence of ocean acoustic propagation conditions on biosonar detection ranges (Chapter 3) and whale noise exposure (Chapter 4). I have focused on two study species, the harbor porpoise (Phocoena phocoena, Chapters 2-3) and the sperm whale (Physeter macrocephalus, Chapters 4-5).The following sections present background information relevant to the research presented in the rest of the thesis, beginning with a review of previous research on the use of echolocation by foraging animals. This review is followed by b...

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The signature of an air gun array: Computation from near‐field measurements including interactions

Cited by 248 publications

References 9 publications

Variable source depth acquisition for improved marine broadband seismic data

Variable source depth acquisition for improved marine broadband seismic data

Stable Q analysis on vertical seismic profiling data

Echolocation-based foraging by harbor porpoises and sperm whales, including effects of noise and acoustic propagation

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