A gravity survey of Wellington City

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Hatherton, T.; Sibson, R.H. 1969 A gravity survey of Wellington City. [s.l.]: [s.n.]. Report / Geophysics Division 57 7p.

Abstract: Residual gravity anomaly maps have been produced for the Thorndon- Lambton-Te Aro and Seatoun areas to enable depths to greywacke basement to be estimated. A residual anomaly map obtained by Rogers (1968) for the Rongotai-Miramar area is also included in this report. Attempts to obtain similar maps for Newtown, Karori and Island Bay basins have failed, probably because of the small sizes of the basins and the inadequacy of the terrain corrections. Densities of overburden are about 2.2 g/cubic cm, of weathered greywacke 2.5 g/cubic m and of unweathered greywacke 2.68 g/cubic cm. Because of the insensitivity of the gravity method (a) at the edges of the basins where errors in terrain correction influence anomalies greatly and (b) in resolving basement relief beneath a basin, only gross estimates of basement depths can be made. Good correlation between residual gravity anomalies and relative ground noise is obtained (auth.)