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Journal Articles Geophysical Journal International Year : 2013

Near-surface study at the Valhall oil field from ambient noise surface wave tomography

Abstract

We used 6 hr of continuous seismic noise records from 2320 four-component sensors of the Valhall 'Life of Field Seismic' network to compute cross-correlations (CCs) of ambient seismic noise. A beamforming analysis showed that at low frequencies (below 2 Hz) the seismic noise sources were spatially homogeneously distributed, whereas at higher frequencies (2-30 Hz), the dominant noise source was the oil platform at the centre of the network. Here, we performed an ambient noise surface wave tomography at frequencies below 2 Hz. We used vertical-component geophones CCs to extract and measure the Scholte waves group velocities dispersion curves that were then processed with a set of quality criteria and inverted to build group velocity maps of the Valhall area. Although Scholte wave group velocity depends on S wave, our group velocity maps show features similar to that was previously obtained from P-wave velocity full-waveform inversion of an active seismic data set. Since the dominant noise source at high frequency (above 3 Hz) was the oil platform, we determined a 2-D S-wave velocity model along a profile aligned with the platform by inverting group velocity dispersion curves of Love waves from transverse-component geophones CCs. We found that S-wave velocity down to 20 m was low and varied along the profile, and could be used to estimate S-wave static.
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Dates and versions

insu-02277520 , version 1 (03-09-2019)

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A. Mordret, M. Landès, N. M Shapiro, S. Singh, O. I Barkved, et al.. Near-surface study at the Valhall oil field from ambient noise surface wave tomography. Geophysical Journal International, 2013, 193 (3), pp.1627-1643. ⟨10.1093/gji/ggt061⟩. ⟨insu-02277520⟩
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