Beanland, S.; Berryman, K.R. 1986 Seismotectonic hazard assessment for lower Clutha power development. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EDS 104 40 p.
Abstract: Seismotectonic hazards pertinent to hydroelectric power development currently being investigated along the lower Clutha River are assessed kin this report. Several faults are present in the vicinity of the proposed power development sites. Those trending north-east commonly have evidence of late Quaternary activity but those trending northwest, although part of the same long-term structural pattern, do not show evidence of late Quaternary activity. Historic and instrumental levels of seismicity are low. Recurrence intervals of faulting cannot be determined accurately, but at least one event has occurred on the Blue Mountain no 1 fault in c. 16,000 years, and the Spylaw fault shows evidence of repeated movement in the past c. 10,000 years. The recurrence interval of faulting on these two structures is longer than 8,000 years and 3,500 years respectively. The probability of a large earthquake centred on one of the active faults in the area, (the maximum credible earthquake of c. Ms = 7.2) in the c. 150 year lifespan of hydrodevelopment structures, is regarded as less than 8.5% and perhaps much less than this value. Ground motions expected at development sites are assessed from the occurrence of the maximum credible earthquake on both local and distant faults and from the seismic intensity of the earthquake that may be expected in the region in the 150 year period. There is a remote probability (,1.8%) that development sites may experience up to 1.0 g vertical acceleration and 0.5 g horizontal acceleration in the next 150 years. There is a moderate to high probability the development sites will experience c. 0.3 g vertical acceleration and 0.2 g horizontal acceleration in the next 150 years. The overall level of seismotectonic hazard in the Lower Clutha is lower than other areas of Central Otago such as Manuherikia and Kawarau Valleys (auth)
