Application of Near-Surface Seismic Characterization to Sparsely Sampled Data Sets

Andrew John Mills

ABSTRACT

The unconsolidated, attenuative, relatively low velocity near surface layers of the Earth cause recording and imaging problems in seismic exploration surveys. Surface waves, recorded as ground roll, have propagated through these near surface layers, and therefore have been affected by these properties of interest. Multichannel analysis of surface waves, or MASW, uses these ground roll amplitudes and the dispersive character of surface waves to estimate near surface shear wave velocities. MASW techniques are applied in this study to synthetic and field data acquired at up to exploration survey scale, to estimate the near surface geometries and velocities. Two field datasets (from the Priddis thumper experiment and Hussar low frequency experiment) are interpolated and filtered to increase dispersion curve resolution. Least squares inversion is applied to the dispersion curve, and 1D near surface velocity profiles are estimated and combined to form 2D velocity profiles over the survey lines. The depth and shear wave velocity of near surface layers and bedrock is estimated to depths greater than 60 m.

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