Estimation of sea‐bed sediment anisotropy using vertical cable seismics

Wang, Hejie; MacBeth, Colin; Li, Xiang‐Yang; Yang, Rong-Jia

doi:10.1190/1.1820936

Cited by 1 publication

(2 citation statements)

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“…In the VSP case, the anisotropic phase-slowness surface local to a receiver array is determined by arrival times measured from a wide-aperture walkaway shot spread (Gaiser 1990;Miller and Spencer 1994;MacBeth 1998;Ohlsen and MacBeth 1998). In the present case, the ray-slowness distributions along the refractors can be determined using a surface shot spread and it is independent of dip (Wang, Li and MacBeth 1999). In the present case, the ray-slowness distributions along the refractors can be determined using a surface shot spread and it is independent of dip (Wang, Li and MacBeth 1999).…”

Section: Introductionmentioning

confidence: 95%

“…The technique requires the assumption of a horizontally layered medium, but may be adapted to accommodate small overburden dips (Sayers 1997). In the present case, the ray-slowness distributions along the refractors can be determined using a surface shot spread and it is independent of dip (Wang, Li and MacBeth 1999). The dip and anisotropy parameters of marine sediments are then estimated by an inversion algorithm.…”

Section: Introductionmentioning

confidence: 99%

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Anisotropic inversion of refracted waves in vertical cable data in the presence of dip

Wang

2002

Geophysical Prospecting

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Refracted arrivals are analysed to estimate the near‐surface anisotropy of marine sediments using a vertical‐cable (VC) configuration. In the presence of dip, the horizontal and vertical ray‐slownesses are obtained from the observed apparent slownesses in the up‐ and downdip directions using a sum or difference at each azimuth. The multiple azimuths generated by a VC geometry permit the ray‐slowness distribution of the marine sediments to be determined. An inversion procedure is developed to provide dip and anisotropy parameters for refractive layers from the measured refraction traveltimes in multilayered azimuthally isotropic and anisotropic media. Two sets of transversely isotropic models are used to analyse the azimuthal variations of apparent and ray slownesses. In the first set, we fix the anisotropic parameters of the models but vary the dip (0°, 5° and 10°) to test the effects of the presence of dip. In the second set, we vary the P‐wave anisotropy strength (5.2%, 10.3%, 15.8% and 22.0%) to examine the sensitivity and accuracy of ray‐slowness approximations which are independent of dip. We test this inversion procedure on synthetic P‐wave VC data calculated for six different models by a finite‐difference method. The results of applications to real VC data acquired from the North Sea are also presented.

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