Seismotectonic evaluation of fault structures in East Otago

Abstract

The work undertaken for this project falls into three parts:

1. Determination of the present rate of strain in the Dunedin area from geodetic data.
2. Investigation of the structure and mechanics of the Hyde Fault and the Rock and Pillar Range, with an assessment of the earthquake potential of this structure.
3. Investigation into the structure and paleoseismicity of the Akatore Fault and an assessment of its earthquake potential.

Part One was undertaken by Dr C Pearson and involved locating and extracting survey records for three triagulation networks around Dunedin and then calculating strain rates from repeated measurements.  The purpose was to determine whether strain rates in the Dunedin area are high enough to be detectable geodetically with existing data, and if not, what are the maximum rates possible.

Part Two used a combination of field observation and computer modelling to investigate the structure and mechanics of the Hyde Fault and Rock and Pillar Range, located about 50km west of Dunedin.  The purpose was to increase our understanding of this structure as a potential source of large earthquakes in the region.

Part Three concentrated on collecting field data on the Akatore Fault, a young fault situated 20km south of Dunedin.  The purpose was to produce an accurate map of the fault trace, determine its structure, and investigate its seismic history.  This is the closest demonstrably active fault to Dunedin City.  Offshore data has also been incorporated into the report.