2016 Kaikoura Earthquake (NZ) Effects & Phenomena. Trevor Matuschka With special acknowledgement Dan Forster (Damsafety Intelligence)

Transcription

1 2016 Kaikoura Earthquake (NZ) Effects & Phenomena Trevor Matuschka With special acknowledgement Dan Forster (Damsafety Intelligence)

2 Contents 1. Kaikoura Earthquake where and what happened 2. Seismic and geologic features 3. Impacts on infrastructure 4. Impacts on dams 5. Impacts on Buildings 6. Concluding Remarks

3 Earthquake Information Date 14 Nov at 12.02am Magnitude Mw7.8, 15 km deep Second largest earthquake in NZ history 2 deaths Located on northeast side of South Island Complex fault rupture process (21 fault segments ruptured) 180km of surface fault rupture Max. horizontal fault displacement 12m Two minutes duration of shaking Max. recorded PGA (horiz) = 1.3g 30cm dynamic displacement (single pulse) Strong fault directivity effects Local tsunami max. runup height of 7m

4 Tectonic Setting

5 Local Tectonic Setting

6 Kaikoura and Wellington City Wellington Australian Plate M7.8 EQ 14 Nov 2016 Pacific Plate Kaikoura

7 Felt Intensity (MMI) California NZ ShakeMap: MMI VIII, Isolated pockets of MMI IX GeoNet: felt reports Courtesy Courtesy GNS Science GNS Science

8 Ground Motions PGA

9 Ground Motions - Wellington

10 21 Fault Ruptures

11 Kekerengu Fault

12 Papatea Fault Uplift

13 Landslides

14 Closed: State Highway 1, Main Trunk Railway Road and rail tunnels Train stranded in tunnel

15 Broken fibre under main trunk rail Fibre-optic Link Repair 84 km of treetop fibre!

16 Cow Island Seaward Landslide

17 Landslide Dams

18 Landslides

19 Hydro Dams Arnold Dilmans Kaniere/McKays Wahapo Cobb Coleridge Waihopai Argyle/Branch Highbank Mangahao Strongest shaking Waitaki Chain Manapouri Scheme

20 Irrigation Dams A number of small irrigation dams and HDPE geomembrane lined reservoirs located within 30km of fault rupture Small number of old small dams (no formal design) A larger number of modern small embankment dams and geomembrane lined ponds (up to 25m high storing 350,000 cubic meters) Typically constructed from low plasticity soils, sometimes gravelly shoulders Dams higher than about 6m typically have a vertical filter zone Construction QA/QC processes required

21 Irrigation Dams - Performance PGAs in excess of 0.7g inferred at some dams In general very minor or no damage for most well constructed embankments Surprisingly some small old dams very close to the fault rupture did not breach Cracking along crest and minor deformation of upstream shoulder evident for less well constructed dams Movement of riprap near dam crest Seich waves overtopped some dams or resulted in significant run-up, but no or only minor resulting damage. Runup over 1m vertical.

22 Irrigation Dams

23 Irrigation Dams

24 Dam Foundation Responses Dam A Dam B Dam C Dam D Dam E Dam F

25 Dam Foundation Response 600km away! (375 miles) Dam A

26 Dam Foundation Response 3-4m (14ft) Dam C 500km (310 miles)

27 Wellington Buildings

28 Buildings A B

29 Wellington Buildings Several multi-storey buildings demolished as a result of earthquake

30 Reclaimed Land Basin edge effects cause of amplified motions on reclaimed land Differing response/behaviour of buildings located on reclaimed land Ok Not OK

31 Concluding Remarks Seismic hazard is real and every earthquake brings new learnings Dams performed well considering level of ground motion, but none impacted directly by fault displacement or landslides Complexity of fault rupture and magnitude of fault displacements had significant impact on land and infrastructure Large number of landslide dams generated but impact low due to low risk downstream Basin edge effects had significant impact on ground response in reclaimed areas and resulted in significant damage to several 8-15 storey buildings.

32 Thank You