Fidelity of ocean bottom seismic observations

Duennebier, F. K.; Sutton, George H.

doi:10.1007/bf01204343

Cited by 78 publications

(87 citation statements)

References 28 publications

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“…The value of a controlled installation with enhanced coupling in the improvement of ocean bottom seismometer performance is unambiguously demonstrated by these data. This conclusion, that seismograms of superior fidelity can be obtained by burial of the sensors beneath the seafloor-water interface, is consistent with all previous experimental and field analyses [Duennebier and Sutton, 1995]. The use of the ROV and the submersible drill permits subseafloor installation comparable to continental seismic stations.…”

Section: Conclusion and The Futuresupporting

confidence: 76%

Corehole seismometer development for low‐noise seismic data in a long‐term seafloor observatory

Stakes

McClain

VanZandt

et al. 1998

Geophysical Research Letters

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Abstract. Longstanding problems unique to marine seismology (in contrast to land-based studies) include high levels of environmental noise, unpredictable instrument placement, short measurement duration, and limited numbers of instruments. Traditional instruments are deployed and recovered from a surface ship with no capability to verify data acquisition until the end of the experiment. They are often poorly sited and usually poorly coupled to the seafloor. Experiments have typically been short in duration with only a minimum number of instruments. The result of these logistical problems is high background noise, sparse data recovery (compared to continental stations), and low fidelity data. In an effort to solve many of these problems, we have developed and deployed "corehole seismometers"(1-90 Hz) into small boreholes drilled by an underwater drilling system, using a tethered Remotely Operated Vehicle (ROV). The results are seismic data with a significantly lower background noise level, a lower threshold for recognition of small events, well-oriented (and useable) horizontal seismograms, and a much longer deployment capability. We present new data from these instruments and compare them with data from two types of traditional instruments deployed from a surface ship. These contemporaneous deployments were conducted during 1996 and 1997 in Monterey Bay.

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Section: Conclusion and The Futuresupporting

confidence: 76%

Corehole seismometer development for low‐noise seismic data in a long‐term seafloor observatory

Stakes

McClain

VanZandt

et al. 1998

Geophysical Research Letters

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“…Trehu and Sutton [1994] demonstrated that auxiliary instrumentation deployed on the seabed in proximity to the OBS sensor package may influence the response function. Duennebier and Sutton [1995] present a theory for vertical and horizontal coupling which considers both translational and rotational motion. They conclude that the effects of rotational motion are inescapable for horizontal sensors and that they must be buried for high-fidelity measurements.…”

Section: Published In 1998 By the American Geophysical Unionmentioning

confidence: 99%

“…Poor coupling manifests itself as resonances in measured signals [e.g., Lewis and McClain, 1977], elevated noise levels [e.g., Latham and Nowroozi, 1968], and distorted vector particle motions due to amplitude and phase corruption. The relative motion may be minimized by careful attention to instrument design [Sutton and Duennebier, 1987;Duennebier and Sutton, 1995] but cannot be entirely avoided due to the compliant nature of the seabed and the typical requirement that an OBS remain on the water/ seabed interface to facilitate deployment and recovery. For vertical motion the seabed and water are constrained to move together, and a suitably designed OBS should exhibit little signal distortion.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the interaction of an ocean bottom seismometer with the seabed

Osler¹,

Chapman²

1998

J. Geophys. Res.

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Abstract. A theory is presented for the coupling between an ocean bottom seismometer (OBS), the sediments upon which it rests, and the surrounding water. Assuming that rotational and tilt effects are negligible (or have been made negligible through instrument design), the response of the OBS to forced harmonic motion is considered in both horizontal and vertical directions. Under these conditions it is concluded that the measured ratio of velocities when the OBS is on the seabed and when it is freely suspended in water (for an identical force) completely characterizes the OBS/seabed interaction. This enables the velocity transfer functions to be directly calculated without recourse to a detailed model of sediment/structure interaction. An OBS was designed and constructed with good coupling to seabed motion and reduction of rocking effects as principal design criteria, including an onboard shaker to conduct in situ coupling experiments. The amplitude and phase of coupling data collected on a clay seabed provide transfer functions due to horizontal and vertical seabed motion and horizontal water motion. In addition, a simple mass-spring-dashpot model of OBS/seabed interaction permits the analysis of amplitude-only coupling data. Good vertical coupling can be achieved over a wide bandwidth by designing the sensor package to have a large hydrodynamic added mass in the vertical. Good coupling to horizontal seabed motion is more difficult to achieve but is possible within a limited bandwidth, even on very soft seabeds. Finally, an example of seismoacoustic noise is presented. Hydrophone signals are compared with horizontal geophone signals received from sources within the ocean and within the seabed, and the differences are explained in terms of the coupling transfer functions.

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“…Duennebier & Sutton (1995) consider a value of 20 m/s appropriate for high-porosity shallow marine sediments in ocean bottom seismometers (OBS) coupling problem analysis. They relate values varying between 10 and 40 m/s from the literature.…”

Section: Physical Properties Of Marine Sediments: Overview Of Literatmentioning

confidence: 99%

“…The near-surface sediments elastic parameters were obtained by averaging the data from Hamilton (1976;1979), Baldwin et al Duennebier and Sutton (1995), Esteves (1996), Ayres and Theilen (1999) and Brazilian offshore data presented on Figure 4 led and processed from Kubena and Post (1992)). …”

Section: Mode Conversion For Down-and Up-going Wavefieldsmentioning

confidence: 99%

Sea-bottom shear-wave velocities and mode conversions

Rodriguez-Suarez¹

2005

Rev. Bras. Geof.

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ABSTRACT. Elastic parameters for shallow marine sediments were obtained from the literature (Hamilton (1976(Hamilton ( ,1979; Hovem et al. (1991); Esteves (1996)) and previously unpublished geotechnical data from offshore Brazil. The Brazilian data showed reasonable agreement with Hamilton's results except in the very shallow (above 10 m) sedimentary section. A second order equation to calculate VS as a function of depth in marine sediments is derived empirically down to a depth of 140 m.Analyses of transmission and reflection coefficients for compressional-and shear-wave energy mode conversion using Zoeppritz equations were performed for both the sea bottom and a typical hydrocarbon reservoir top of Tertiary age. It is concluded that most S-wave reflection data recorded on the ocean floor by OBC is related to upcoming energy converted at an interface at depth and not from a downgoing shear conversion at the ocean floor.It was also concluded that, using elastic assumptions, mode conversion (both P-to S-and S-to P-) of the up going energy is negligible in the shallow (above 160 m) sediments.Keywords: V S in marine sediments, mode conversion. (1976,1979); Hovem et al. (1991); Esteves (1996)) e dados geotécnicos marítimos inéditos do Brasil. Os dados brasileiros mostraram uma correlação razoável com os resultados de Hamilton exceto para a seção sedimentar muito rasa (acima de 10 m). Uma equação de segunda ordem para calcular V S como função de profundidade foi derivada empiricamente até uma profundidade de 140 m. RESUMO. Parâmetros elásticos para sedimentos marinhos rasos foram obtidos de literatura (HamiltonAnálises de coeficientes de transmissão e reflexão para conversão de modo em ondas compressionais e cisalhantes usando equações de Zoeppritz foram realizadas para o fundo do mar e um topo de reservatório de idade Terciária típico. Conclui-se que a maior parte das ondas-S refletidas e registradas no fundo do mar por cabos de fundo oceânico está relacionadaà energia ascendente convertida em uma interface profunda e não de uma onda-S descendente convertida no fundo do mar.Foi concluído também que, usando premissas elásticas, a conversão de modo (tanto P-para S-quanto S-para P-) da energia ascendenteé negligenciável nos sedimentos rasos (acima de 160 m).Palavras-chave: V S em sedimentos marinhos, conversões de modo.Petrobras / UN-Rio / Atp-Ro / Res,

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Fidelity of ocean bottom seismic observations

Cited by 78 publications

References 28 publications

Corehole seismometer development for low‐noise seismic data in a long‐term seafloor observatory

Corehole seismometer development for low‐noise seismic data in a long‐term seafloor observatory

Quantifying the interaction of an ocean bottom seismometer with the seabed

Sea-bottom shear-wave velocities and mode conversions

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