Geodetic monitoring of earth deformation across the Wairau Fault

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Otway, P.M. 1973 Geodetic monitoring of earth deformation across the Wairau Fault. Wellington: New Zealand Geological Survey. Report NZGS 62; New Zealand Geological Survey report EDS 10. 41 p.

Abstract: In 1970 May a section of the first order triangulation spanning the eastern part of the Wairau Fault was reobserved. A comparison was made with the initial first order survey of 1938 April. As a further comparison, the results of a series of lower order surveys connecting on to the same points made immediately prior to 1885 were examined and recomputed in terms with the 1938 survey. In general, the 1885-1938 period was characterised by possible right-lateral shear across the Wairau Fault and left-lateral shear within the block between Wairau and Awatere Faults. Over the whole figure the shear is left-lateral. There exists also possible shortening parallel to the Wairau Fault on both sides with some lengthening across it and shortening in the area between the two faults. The results of the 1938-1970 period are much more reliable and indicate a reversal in shear direction, with possible slight left-lateral shear across the Wairau Fault and a little right-lateral shear in the block between the Wairau and Awatere Faults. The most significant characteristic in the shortening along the north-western side of the Wairau and lengthening along the south-eastern side, combined with some lengthening normal to the fault int hat area. The rates of strain in the first period are approximately 0.4-1.6 x 10-6 per year, and, in the second period, 0.3-1.0 x 10-6 per year.