Central Otago and Queenstown
Total Page:16
File Type:pdf, Size:1020Kb
General distribution and characteristics of active faults and folds in the Queenstown Lakes and Central Otago districts, Otago DJA Barrell GNS Science Consultancy Report 2018/207 March 2019 DISCLAIMER This report has been prepared by the Institute of Geological and Nuclear Sciences Limited (GNS Science) exclusively for and under contract to Otago Regional Council. Unless otherwise agreed in writing by GNS Science, GNS Science accepts no responsibility for any use of or reliance on any contents of this report by any person other than Otago Regional Council and shall not be liable to any person other than Otago Regional Council, on any ground, for any loss, damage or expense arising from such use or reliance. Use of Data: Date that GNS Science can use associated data: February 2019 BIBLIOGRAPHIC REFERENCE Barrell DJA. 2019. General distribution and characteristics of active faults and folds in the Queenstown Lakes and Central Otago districts, Otago. Lower Hutt (NZ): GNS Science. 99 p. Consultancy Report 2018/207. Project Number 440W1521 2019 CONTENTS EXECUTIVE SUMMARY ....................................................................................................... V 1.0 INTRODUCTION ........................................................................................................1 1.1 Background .....................................................................................................1 1.2 Scope and Purpose .........................................................................................4 2.0 INFORMATION SOURCES ........................................................................................6 3.0 GEOLOGICAL OVERVIEW ........................................................................................7 3.1 Rocks and Landforms ......................................................................................7 3.2 Recognition of Active Faults and Folds ............................................................ 8 3.3 Seismicity ...................................................................................................... 11 4.0 CLASSIFICATION OF ACTIVE FAULTS AND FOLDS ............................................ 13 4.1 Descriptive Classification ............................................................................... 13 4.2 Activity Classification ..................................................................................... 14 4.3 As-Yet Undetected Active Faults ................................................................... 17 4.4 Earthquake Magnitudes ................................................................................. 17 5.0 DISTRIBUTION AND CHARACTERISTICS OF ACTIVE FAULTS .......................... 19 5.1 Overview ....................................................................................................... 19 5.2 Comparison with Previous Assessments ....................................................... 29 5.3 Assessment of Fault Activity Estimates.......................................................... 29 5.4 Discussion of Fault Activity Close to Population Centres ............................... 30 5.4.1 Queenstown Area ............................................................................................ 30 5.4.2 Wanaka and Hawea Area ............................................................................... 30 5.4.3 Upper Clutha Valley ........................................................................................ 34 5.4.4 Clyde and Alexandra Areas ............................................................................. 35 5.4.5 Roxburgh Area ................................................................................................ 36 5.4.6 Maniototo Area ................................................................................................ 36 6.0 IMPLICATIONS FOR HAZARDS.............................................................................. 38 7.0 CONCLUSIONS ....................................................................................................... 39 8.0 ACKNOWLEDGEMENTS ......................................................................................... 40 9.0 REFERENCES ......................................................................................................... 40 FIGURES Figure 1.1 The tectonic setting of the Queenstown Lakes and Central Otago districts. ................................ 2 Figure 1.2 Illustrations of recent historical fault rupture deformation of the ground surface in New Zealand. 3 Figure 1.3 A northward oblique aerial view of ground-surface deformation across the Ostler Fault Zone, in the Waitaki District of Canterbury ................................................................................................. 4 Figure 3.1 Diagrams illustrating styles of active faults and folds. .................................................................. 9 Figure 3.2 Illustrations of faults exposed in investigation trenches. ............................................................. 10 GNS Science Consultancy Report 2018/207 i 2019 Figure 3.3 Recorded earthquakes in the southern South Island over the past 30 years ............................. 12 Figure 5.1 General distribution of active faults and folds in the Queenstown Lakes and Central Otago districts (northern panels). .......................................................................................................... 20 Figure 5.2 General distribution of active faults and folds in the Queenstown Lakes and Central Otago districts (centre panels). ............................................................................................................. 21 Figure 5.3 General distribution of active faults and folds in the Queenstown Lakes and Central Otago districts (southern and eastern panels). ..................................................................................... 22 Figure 5.4 Views of a geological investigation trench excavated across the NW Cardrona Fault in the Kawarau valley at Gibbston in 1984. .......................................................................................... 31 Figure 5.5 Map views highlighting the location of a suspected monocline fold through Wanaka township .. 32 Figure 5.6 A view east across a likely monocline fold at Wanaka Cemetery. .............................................. 33 Figure 5.7 A view east across a geologically-young fault offset of hillslope landforms on the Highland Fault, in the catchment of Fern Bern .................................................................................................... 34 Figure 5.8 Views of a Dunstan Fault Zone monocline fold immediately northeast of Clyde. ....................... 35 Figure 5.9 View of the scarp of the Stranraer Fault (Waihemo Fault Zone) across middle to high-level terraces of the Little Kye Burn valley .......................................................................................... 36 TABLES Table 5.1 Categories and terms used in this report to describe active faults and folds in the Queenstown Lakes and Central Otago districts. ............................................................................................. 23 Table 5.2 Summary of evidence and estimated deformation characteristics of active faults and folds recognised in the Queenstown Lakes and Central Otago districts. ............................................ 24 APPENDICES APPENDIX 1 GIS DATASET ................................................................................... 47 APPENDIX 2 COMMENTARY ON ACTIVE FAULT MAPPING ............................... 48 A2.1 Background Information ................................................................................. 48 A2.2 Backbone fault (feature 45; Figure 5.3) .......................................................... 49 A2.3 Beaumont River fault (feature 46; Figure 5.3) ................................................ 50 A2.4 Blackstone Fault (feature 31; Figures 5.2–5.3) .............................................. 50 A2.5 Blue Lake Fault (feature 23; Figures 5.2–5.3) ................................................ 51 A2.6 Cardrona-Hawea fault (feature 11; Figures 5.1–5.2) ...................................... 52 A2.7 Cluden fault zone (feature 19; Figure 5.2) ...................................................... 52 A2.8 Cross Eden fault (feature 34; Figure 5.3) ....................................................... 53 A2.9 Dansey Pass Fault (feature 36; Figure 5.3) ................................................... 54 A2.10 Dingle Fault (feature 15; Figure 5.1) .............................................................. 54 A2.11 Dunstan Fault Zone (feature 22; Figures 5.2–5.3) ......................................... 55 A2.12 Galloway fault zone (feature 29; Figures 5.2–5.3) .......................................... 59 A2.13 Garibaldi Fault (feature 32; Figure 5.3) .......................................................... 61 A2.14 Garvie Fault (feature 27; Figure 5.2) .............................................................. 61 A2.15 Gimmerburn Fault Zone (feature 33; Figure 5.3) ............................................ 62 A2.16 Goodger Fault (feature 18; Figures 5.1–5.2) .................................................. 62 ii GNS Science Consultancy Report 2018/207 2019 A2.17 Grandview Fault (feature 12; Figures 5.1–5.2) ............................................... 63 A2.18 Hawkdun Fault (feature 25; Figure 5.3).........................................................