Precise gravity measurements between Lyttelton and Westport, South Island

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Woodward, D.J.; Carman, A.F. 1982 Precise gravity measurements between Lyttelton and Westport, South Island. [s.l.]: [s.n.]. Report / Geophysics Division 163 17 p

Abstract: Gravity observations have been made on benchmarks 5-6 km apart between Lyttelton and Westport, including a closed loop between Springs Junction, O'Sullivans Bridge, Inangahua and Reefton. Less precise measurements have been made on Geological Survey's fault monitoring patterns at Fowlers, Guide Hut and St James near Hanmer. The initial readings were made in May 1981, with some of the readings being repeated in January 1982 because of tares of the gravity meter during the initial survey. The observations on the fault monitoring patterns were made during the second set of readings. All the observations were made with LaCoste and Romberg model D gravity meter, D37, and were made in a ladder sequence day by day with at least three readings on each station. The sequence and internal consistency of the readings was such that, after the effects of blunders and tares were removed, and appropriate weighting applied, the standard error of the calculated difference of gravity between any two stations was less than 0.15 micro N/kg. This is for points at either end of the line, 340 km long, incorporating 62 stations. The standard error of the difference of gravity between adjacent stations is about 0.04 micro N/kg. The misclosure around the closed loop of 190 km with 44 observation points, near Murchison and Reefton, was 0.10 +- 0.11 micro N/kg