2019 – Fault Investigation Practice in Australia and New Zealand: Why Australian Dam Owners and Operators Should Care About Collecting Active Fault Data

D. Ninis, D. Clark

The ANCOLD Guidelines (2019) require that active and neotectonic faults which could significantly
contribute to the ground-shaking or ground-displacement hazard for a dam should be accounted for in seismic hazard assessments. While geological and geomorphological field investigations along suspected active fault structures are undertaken as a matter of course in New Zealand, this practice is relatively uncommon in Australia. Granted, rates of tectonic processes are greater in New Zealand than in intraplate Australia. However, moderate to large and damaging earthquakes are not uncommon in the Australian record; there have been ~26 earthquakes of magnitude >M6 in the last 150 years (~1 event every ~6 years) and similar events might be expected in the future. We present examples of investigations undertaken to better understand earthquake hazard for two faults – previous studies on the Wellington Fault, New Zealand, and new data from recent investigations of the Avonmore Scarp, southeast Australia. We report the results from these studies and discuss how the collection of similar data on faults proximal to Australian dams would allow dam owners and operators to better quantify seismic hazard and, thereby, more meaningfully comply with the ANCOLD guidelines.