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Simon Cox: New Zealand Mountains Falling Down

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Day 1 - Presented to Sustainable Summits 2016
Simon Cox: New Zealand Mountains Falling Down

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Simon Cox: New Zealand Mountains Falling Down

  1. 1. GNS Science New Zealand Mountains Falling Down Simon Cox Principal Scientist, GNS Science
  2. 2. GNS Science Atua
  3. 3. GNS Science New Perspectives
  4. 4. GNS Science Geophysics 301
  5. 5. GNS Science WEST EASTGeophysics 401
  6. 6. GNS Science WEST EAST
  7. 7. GNS Science Mountains Presently Growing c. 5 mm/yr
  8. 8. GNS Science Contemporary GPS Velocities and Strain Rate Velocities relative to Australian Plate Max. shear strain rate Beavan & Haines (2001)Beavan et al. (1999)
  9. 9. GNS Science NZ in 4 million years…. Buckle up for the ride....? A cricket pitch of displacement every 500 years
  10. 10. GNS Science After Little 2004
  11. 11. GNS Science
  12. 12. GNS ScienceCox & Barrell (2007) Southern Alps
  13. 13. GNS ScienceCox et al. 2012 Tectonics 31: doi:10.1029/2011TC003038
  14. 14. GNS Science It can be dangerous in an active collision zone! Aoraki/Mt Cook 1991 12 million cubic metres Franz Josef Glacier town Waiho River
  15. 15. GNS Science Temporary storage areas for sediment which evolve and change through time. Alluvial Fans & Debris Flows Cass Valley
  16. 16. GNS Science Te Horo Dart Valley
  17. 17. GNS Science
  18. 18. GNS ScienceSH6 Pipson Creek, April 2006 Pipson Ck SH6, 2006
  19. 19. GNS Science Differences in fan type (and hazards) depend largely on whether there is a mechanism for removing sediment from the fan systemAlluvial Fans 1913 Aoraki/Mt Cook Village Hermitage
  20. 20. GNS Science Fan Landforms 6% of Otago
  21. 21. GNS Science Occupying fan landscapes
  22. 22. GNS Science Landslides & Lateral Spreading • Downwasting ice, removes slope support • Widespread and continued along lateral moraines • Propagation upwards into bedrock slopes Ball Road Ball Hut
  23. 23. GNS Science Mueller Huts
  24. 24. GNS Science Malte Brun Hut Summer 1964-65
  25. 25. GNS Science Malte Brun Hut Site 2014 ????
  26. 26. GNS Science Rock Avalanches 4% of MCNP affected by rock avalanches in last ~50 years 22-27° farböschung ‘angle of reach’ common, as low as 16°across snow Significant recent increase in rate Allen, Cox, Owens (2011) Landslides 8: 33-48 40-50° >50°
  27. 27. GNS Science Beatrice, Nov 2004 When Rockfall gets Bigger
  28. 28. GNS Science
  29. 29. GNS Science 2008 was a busy year Vampire Jan 7 & 13 Douglas 18 Feb Spencer 6-7 Apr Halcombe 24 Apr
  30. 30. GNS Science
  31. 31. GNS Science Vampire Debris Distinct lobes 300,000 m2
  32. 32. GNS Science Source
  33. 33. GNS Science
  34. 34. GNS Science Aoraki - Hillary Ridge July 2014 Gardiner Hut
  35. 35. GNS Science MCNP Rock Avalanches
  36. 36. GNS Science Rock Avalanches Slope >50°
  37. 37. GNS Science Temperature Effects Vampire seismographs
  38. 38. GNS ScienceMcSaveney, Cox & Hancox work in progress LOCATION Date Aoraki/Mt Cook 1873 Mt Isobel I c. 1950-55 Mt Isobel II c. 1965 Mt Walter-Green 1972 Mt Vancouver 1974 or 75 Murchison Glacier 25/12/75 *1 Aoraki/Mt Cook 14/12/91 Mt Fletcher I 2/05/92 Mt Fletcher II 16/09/92 *2 Mt Thomson 22/02/96 Mt Adams 6/10/99 Vampire 2003 Mt Beatrice 23/11/04 Vampire 7-13/01/08 Douglas Peak 18/02/08 Mt Spencer 6-7/04/08 Mt Halcombe 24/04/08 Rock Avalanches last 60 years
  39. 39. GNS Science Role of De-Glaciation & Accelerated Climate Change?
  40. 40. GNS Science Fiordland Earthquake 350 km away, MM III-IV Shaking ~0.4-2.3%g T decay 0.9 ± 0.2 °C over 5 days Role of Elastic Deformation?
  41. 41. GNS ScienceMcSaveney, Cox & Hancox work in progress The Seismic Cycle & 330 yr Alpine Fault earthquakes? NZ earthquake shaking Rock avalanche frequency
  42. 42. GNS Science Given the considerable number of spontaneous rock avalanche events, collapses should be widespread when a major earthquake does eventually shake the central Southern Alps. Hooker Glacier, 1893 Burton Brothers Collection, Te Papa
  43. 43. GNS Science Alpine Fault One of the longest, straightest, fastest moving plate boundary transform faults in the world. •Accommodates 75% of plate motion • Rapid slip rate of 20-30 mm/year
  44. 44. GNS Science Earthquakes on the Alpine Fault • Evidence of past earthquakes preserved in the landscape • Last ruptured in 1717 A.D. • ~380 km rupture = Mw8 • Regular Return Interval ~260-400 years (average 329 ± 68 years) • No major event in past 298 years • Likelihood ~30% in next 50 years See Berryman et al. 2012 (Science); Howarth et al. 2012 (Geology) amongst other recent work
  45. 45. GNS Science Mw8 Alpine Fault Earthquake scenario • Synthetic isoseismals   (MM intensity) for a  MW 8 earthquake • Southern Alps and  Westland = MM IX  (locally X) • Christchurch &  Central Otago  MM VI‐VII • Dunedin = MM V One possible scenario for a large Alpine Fault earthquake suggested by Tim Davies, Canterbury University
  46. 46. GNS Science Geomorphic consequences • Geomorphic impacts of Alpine Fault earthquakes may persist for decades Tsunami Rock avalanche Dambreak flood Severe sedimentation Scenario provided by Prof T. Davies One possible scenario for a large Alpine Fault earthquake suggested by Tim Davies, Canterbury University
  47. 47. GNS Science Earthquake Induced Landslides Cascade Mw?? c.660AD 750 million m3 Murchison Mw7.8 1929 Lake Stanley 18 million m3 Barth 2013 Landslides Hancox et al. 2002 BNZSEE 35(2):59-95
  48. 48. GNS SciencePhoto: V. Kennett Perfect Storm?
  49. 49. GNS Science MCNP Huts
  50. 50. GNS Science MCNP Huts Are there are other management options?
  51. 51. GNS Science
  52. 52. GNS Science
  53. 53. GNS Science
  54. 54. GNS Science Hazards to consider GEOLOGICAL • Earthquakes • Rock Avalanches • Rock fall • Landslides • Lateral spreading • Debris flows/floods • Tsunami (lake) METEOROLOGICAL • Snow Avalanches • Lightening • Hail storm • Wind • Flooding • Geomagnetic storm WILDFIRE
  55. 55. GNS Science Hazardscape Hazard Assessment: Knee-jerk (± emotion) vs Holistic approaches
  56. 56. GNS Science Appropriate Time Scale 10-20 yrs (<< 50 yr Building Code)

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