Gravity survey of the Middle Wairarapa

Abstract

A contour map of the residual gravity anomalies in the middle Wairarapa from Carter ton to Woodville is presented, and the tectonic implications are discussed. It is considered that the West Wairarapa Trough probably marks a zone of shear, and that the disposition of the Pahiatua and Masterton Basins may be interpreted as evidence of translation along the line of that trough of about 40 miles. It is suggested that the effects of the 1855 Wairarapa and 1931 Napier earthquakes, and the emergence of the Waewaepa Range in the post-Castlecliffian, may all be due to horizontal crustal movements.