Blick, G.H. 1990 Results from horizontal monitoring across the central section of the Ostler Fault Zone. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EDS 129 24 p.
Abstract: Repeated triangulation surveys across the Ohau A Power Station area and to the east enable the horizontal deformation for up to the past 90 years to be determined. Results from 3rd and 4th order networks, initially surveyed during the 1870's and 1880's and repeated in the 1960's indicate a regional strain model, significant at 100%, of 0.34ppm/yr maximum engineering shear strain with the azimuth of the axis of relative contraction at 108 degrees. This result is consistent with results using similar data from an area to the east of the Ostler fault zone between Lakes Pukaki and Tekapo. Results from the Ostler fault monitoring pattern, surveyed four times between 1964 and 1984 using a combination of triangulation and trilateration, show that the deformation in the vicinity of the fault may be more complex; the data do not fit a uniform strain model well and block model is a better fit to the data. A model is suggested that may explain these results; in the area of the Ostler fault zone and to the west the regional strain (0.3ppm/yr) is concentrated on the Ostler fault as creep at a rate of c. 1mm/yr. Results from vertical monitoring across the fault zone show vertical deformation adjacent to faults within the zone, supporting the model of creep occurring on the fault.
