Mansergh, G.D.; Read, S.A.L. 1973 The Ostler fault zone, S109: ground movement near the Ohau A powerhouse site. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 151 18 p.
Abstract: The Ostler Fault Zone is an active zone of Quarternary faulting which runs along the western side of the Mackenzie basin. The zone extends for at least 35 miles from the head-waters of the Twizel River in the north to the Ahuriri River in the south. A set of folds (on the upthrown side) of some of the fault traces has been recognized and these folds are associated directly with the individual fault traces. An alignment of earthquake foci, all recorded since the filling of Lake Benmore in 1964, have been mapped by Adams (1973) within or immediately west of the zone. The Ohau A powerhouse on the Upper Waitaki Power Development scheme is situated within the fault zone and is very close to fault scarps formed in the last 14,000 years. Oborn (1965) reported on the stability risk to engineering structures associated with fault movement, the frequency of fault movement, and modifies the zone classification proposed in his report. A regional geological map is appended to this repot together with more detailed maps showing fault traces and associated features between the Ohau River and Mount Olster. A series of terrace profiles across the fault scarps is also included. Topographic data for the report was obtained from the A.P. 748 series at a scale of 1'' = 100' with 2' contours. Where the A.P. 748 series did not exist A.P. 144 series at a scale of 1'' = 20 hain and 10'' contours was used. (auth)
