Birdlings Flat seismic refraction survey: 1973

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Broadbent, M.; Haines, A.J. 1976 Birdlings Flat seismic refraction survey: 1973. : . Report / Geophysics Division 116 7 p.

Abstract: A seismic refraction survey was conducted at the seaward end of Lake Forsyth, in the Birdlings Flat area, to investigate the local nature of the buried upper boundary of the Akaroa volcanic rocks. Three seismically distinct layers were identified below the survey area. These were dry soils and loess, through which seismic compressional waves propagated with a velocity of 0.2 km/s, water saturated gravels, with associated velocity of 2.0 km/s, and Akaroa volcanics, with associated velocities in the range from 3.0 to 4.0 km/s. The thickness of the unsaturated soils was of the order of one metre. The detected thickness of the sediments over the Akaroa volcanic rocks varied from zero, on the flanks of the gully in which the survey was conducted, to a maximum of 37 metres. The maximum thickness occurred over a deep steep sided buried channel, which passed through the surveyed area approximately following the line of the centre of the gully.