Broadbent, M. 1972 Thermal power development : the Marsden Point seismic refraction survey of February 1972. : . Report / Geophysics Division 78 11 p.
Abstract: The seismic refraction survey in the vicinity of Marsden Point power station detected three seismically distinct subsurface layers. Immediately below the ground surface were dry or unsaturated sands and rubble through which P-waves propagated with velocities in the range 0.15 to 0.34 km/s. The base of this layer was near mean sea level (datum). Below mean sea level were thick deposits of water saturated sands with some clay, silt, gravel and organic content. This overlaid greywacke. Velocities ranges for P-wave propagation in these two layers were 1.37 to 1.74 km/s and 3.29 to 4.51 km/s respectively. The greywacke-sand boundary, that of principal interest, was characterised by marked depth variations. In the southern survey area it varied between 20 and 72 metres (65 and 235 feet) below datum, the deepest parts being below the southern part of the survey area. In the northern area depths varied between 20 and 45 metres (65 and 145 feet) below datum. In the northern survey area the course of a deep channel has been further defined, although knowledge of the course and extent of the channel is still very limited. (auth)