Ocean Bottom Marine Seismic Methods

2021 ◽  
pp. 220-271
Author(s):  
Ian Jack
2015 ◽  
pp. 175-208 ◽  
Author(s):  
J.O.A. Robertsson ◽  
R. Laws ◽  
E. Kragh

1976 ◽  
Vol 13 (11) ◽  
pp. 1545-1555 ◽  
Author(s):  
R. M. Clowes ◽  
S. J. Malecek

A marine seismic system for recording near-vertical incidence to wide-angle reflected waves and refracted waves with penetration from the ocean bottom to the upper mantle (deep seismic sounding or DSS) has been developed. Signals from six individual hydrophones suspended at 45 m depth from a 600 m cable trailed behind the receiving ship are recorded in digital form. Using charges ranging from 2.3 to 280 kg, two reversed DSS profiles were recorded in the region of Explorer ridge during 1974. A preliminary interpretation of the profiles based on first-arrival information in the range 4 to 80 km has been made.The reversed profile run across the ridge showed no anomalous effects as the ridge was crossed; the profile on Juan de Fuca plate, paralleling the ridge, exhibited traveltime branch offsets and delays. These have been interpreted as due to faulting with a vertical component of offset of about 4 km. The reversed upper mantle velocities are 7.85 and'7.30 km/s indirections perpendicular and parallel to the ridge. Anisotropy is proposed to explain these different velocities and gives a 7% anisotropic effect. The data require that 'layer 2' comprise at least two layers with velocities of 4.13 km/s and 5.25 km/s and individual depth extents ranging from 1 to 2 km. Compared with crustal sections from other ridge areas, the interpretation gives a thick 'layer 3' (up to 6 km) near the ridge crest. The sub-bottom thickness of the oceanic crust varies between 7 and 9 km, except in the faulted region, where the 7.30 km/s material is present less than 3 km from the bottom.


2009 ◽  
Vol 49 (2) ◽  
pp. 572
Author(s):  
Andrew Long ◽  
Guillaume Cambois ◽  
Gregg Parkes ◽  
Anders Mattsson ◽  
Terje Lundsten

The sea-surface reflection generates interferences between up- and down-going waves that ultimately limit the bandwidth of marine seismic data. This phenomenon known as ghosting actually occurs twice—on the source side and on the receiver side. Ghost attenuation or elimination to increase the signal bandwidth has been the focus of extensive research. The receiver ghost can be removed using dual-sensor ocean-bottom devices (Barr and Sanders, 1989), a dual-sensor towed streamer (Carlson et al, 2007) or an over/under streamer acquisition (Brink and Svendsen, 1987). The over/under technique can also be used to remove the source ghost (Moldoveanu, 2000) but it requires flip-flop shooting of two sources at two different depths, ultimately halving the survey shot-point density. Alternatively, the source ghost can be attenuated using a beam steering technique originally developed some 60 years ago for dynamite land acquisition (Shock, 1950). The principle is to detonate charges at various depths in a sequence that constructively builds the down-going wave at the expense of the up-going wave. This way the energy of the ghost (the surface-reflected up-going wave) is reduced compared to that of the primary pulse. In this paper we adapt the beam steering approach to airgun arrays in the marine environment.


2020 ◽  
Vol 223 (3) ◽  
pp. 1888-1898
Author(s):  
Kirill Gadylshin ◽  
Ilya Silvestrov ◽  
Andrey Bakulin

SUMMARY We propose an advanced version of non-linear beamforming assisted by artificial intelligence (NLBF-AI) that includes additional steps of encoding and interpolating of wavefront attributes using inpainting with deep neural network (DNN). Inpainting can efficiently and accurately fill the holes in waveform attributes caused by acquisition geometry gaps and data quality issues. Inpainting with DNN delivers excellent quality of interpolation with the negligible computational effort and performs particularly well for a challenging case of irregular holes where other interpolation methods struggle. Since conventional brute-force attribute estimation is very costly, we can further intentionally create additional holes or masks to restrict expensive conventional estimation to a smaller subvolume and obtain missing attributes with cost-effective inpainting. Using a marine seismic data set with ocean bottom nodes, we show that inpainting can reliably recover wavefront attributes even with masked areas reaching 50–75 per cent. We validate the quality of the results by comparing attributes and enhanced data from NLBF-AI and conventional NLBF using full-density data without decimation.


2021 ◽  
Vol 18 (4) ◽  
pp. 492-502
Author(s):  
Dongliang Zhang ◽  
Constantinos Tsingas ◽  
Ahmed A Ghamdi ◽  
Mingzhong Huang ◽  
Woodon Jeong ◽  
...  

Abstract In the last decade, a significant shift in the marine seismic acquisition business has been made where ocean bottom nodes gained a substantial market share from streamer cable configurations. Ocean bottom node acquisition (OBN) can acquire wide azimuth seismic data over geographical areas with challenging deep and shallow bathymetries and complex subsurface regimes. When the water bottom is rugose and has significant elevation differences, OBN data processing faces a number of challenges, such as denoising of the vertical geophone, accurate wavefield separation, redatuming the sparse receiver nodes from ocean bottom to sea level and multiple attenuation. In this work, we review a number of challenges using real OBN data illustrations. We demonstrate corresponding solutions using processing workflows comprising denoising the vertical geophones by using all four recorded nodal components, cross-ghosting the data or using direct wave to design calibration filters for up- and down-going wavefield separation, performing one-dimensional reversible redatuming for stacking QC and multiple prediction, and designing cascaded model and data-driven multiple elimination applications. The optimum combination of the mentioned technologies produced cleaner and high-resolution migration images mitigating the risk of false interpretations.


2020 ◽  
Vol 12 (17) ◽  
pp. 2816
Author(s):  
Minao Sun ◽  
Shuanggen Jin

Ocean bottom seismometer (OBS) can record both pressure and displacement data by modern marine seismic acquisitions with four-component (4C) sensors. Elastic full-waveform inversion (EFWI) has shown to recover high-accuracy parameter models from multicomponent seismic data. However, due to limitation of the standard elastic wave equation, EFWI can hardly simulate and utilize the pressure components. To remedy this problem, we propose an elastic full-waveform inversion method based on a modified acoustic-elastic coupled (AEC) equation. Our method adopts a new misfit function to account for both 1C pressure and 3C displacement data, which can easily adjust the weight of different data components and eliminate the differences in the order of magnitude. Owing to the modified AEC equation, our method can simultaneously generate pressure and displacement records and avoid explicit implementation of the boundary condition at the seabed. Besides, we also derive a new preconditioned truncated Gauss–Newton algorithm to consider the Hessian associated with ocean bottom seismic 4C data. We analyze the multiparameter sensitivity kernels of pressure and displacement components and use two numerical experiments to demonstrate that the proposed method can provide more accurate multiparameter inversions with higher resolution and convergence rate.


1978 ◽  
Vol 15 (1) ◽  
pp. 78-85 ◽  
Author(s):  
George A. McMechan

The use of direct arrivals and multiple reflections that have travelled completely in water from source to receiver to determine epicentral distances is a standard technique in the analysis of marine seismic profiles. The configuration of a source at the air–water interface and a seismometer at the water–sediment interface is investigated in the ray parameter – distance plane and the travel time – distance plane. Vertical component synthetic seismograms are computed by the Cagniard – de Hoop algorithm and are compared with seismograms recorded at the ocean bottom. The results explain the prominent features of the observed wavetrains, including the asymptotic behaviour of arrivals, the location of caustics and the variable observability of arrivals as a fu nction of distance.


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