A Tale of Two Earthquakes. Christchurch - Sept and Feb. 2011

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1 A Tale of Two Earthquakes Christchurch - Sept and Feb by Ron Mayes

2 New Zealand On Edge of Pacific Plate Christchurch Earthquake epicentre Christchurch GNS Science

3 4 Sep 2010 M7.1 Darfield Earthquake 4:36 am no fatalities 30 km West of Christchurch E-W striking fault, previously unmapped Mostly URM damage and residential damage due to liquefaction. Cost estimate $6-$10 billion (direct + indirect)

4 An Irish Bar that was Destroyed in February

5 12:51 pm 22 February 2011 The second event was much closer to downtown Christchurch

6 CBD

7 Level of Shaking 8 Seconds of strong shaking whereas Japan was 3 minutes Measured shaking in the Central Business District was similar to a design earthquake in the Bay Area. The measured shaking was about 50% greater than the design level for Christchurch as Christchurch was thought to be a lower seismic zone.

Sa (g) Short intense shaking - CBD Short Duration, about 8 sec of strong motion East-West North-South 1.6 1.4 1.

8 Sa (g) Short intense shaking - CBD Short Duration, about 8 sec of strong motion East-West North-South Feb 2011 Vertical Sep Period (s) Image courtesy of GNS

9 Sa (g) Comparison with Design Earthquake Berkeley DBE Christchurch 500 yrs Sacramento DBE Period (s)

10 Christchurch Central Business District (CBD) Approx. 6,000 companies or institutions with over 50,000 employees. This is 25% of the total employment in the city. No one has been back in 8 weeks

11 CBD - San Francisco Equivalent Area

12 A Series of Damage Photos in the Central Business District (CBD)

15 Images courtesy of Kelvin Berryman, GNS Science

17 Striking losses before & after Anonymous photos

18 Striking losses before & after

19 Grand Chancellor - Corner dropped 2.5ft -Reinforced concrete -19 stories -mid-1980s -Core wall (up to 7 th story) -Perimeter frame (above 7 th story) -Corner dropped 2.5

20 Concrete CTV (1986) Green Tagged in Sept.

21 Concrete Pyne Gould (pre-1970s)

22 Concrete Pyne Gould (pre-1970s)

23 Concrete Parking Structure

24 Concrete Structures Column Shear Failures 5 more seconds of shaking and another collapsed building

25 Concrete Stuctures - Column Shear/Joint Failure 5 more seconds of shaking and another collapsed building Some Images courtesy of Weng Y Kam

26 URM Performance Pier Shear Failure All Collapse Hazards in Future Shaking

27 Concrete Structures Good Performers

28 Concrete Structures Good Performers

29 Retrofitted Unreinforced Masonry Buildings (URM s) Good Performance

30 Performance of Retrofitted URM s Heavy Damage 28% Moderate Damage 32% Minor Damage 30% Insignificant Damage 10%

31 Retrofits with Major Damage EERI/PEER Briefing on on February Christchurch NZ Earthquake NZ

32 Retrofitted URM Performance Failure at Gable VERY COMMON

33 Overview of Port Hills and Christchurch 33

34 Liquefied Area: 22 Feb 2011 Earthquake

35 Extent of Liquefaction Image courtesy of IPENZ

36 Extent of Liquefaction ME! Some Images courtesy of Ron Mayes & James Dismuke

37 Severe Liquefaction in Suburbs (1) Widespread and very severe liquefaction Large areas covered by thick sand ejecta Severe damage to buried lifelines Large subsidence in some suburbs

38 Severe Liquefaction in Suburbs (2) Large settlement of residential houses (global and differential)

39 Liquefaction / Differential Settlement Both buildings undamaged but rotated at the foundation level causing displacements shown at the top floor 20 in Can if be fixed? How? What will happen the next time? 450mm 250mm 10 in.

40 CBD Case Studies: CS-5 (2) 1.8 deg Moderate/severe liquefaction Lateral movement: 6 in. Tilt: deg Differential settlement 6 in.

41 CBD Case Studies: CS-6 (2) 17 in Moderate/severe liquefaction Differential settlement: 17 in. 17 in.

42 Concrete Structurces Crowne Plaza 45 Long Driven Piles 30 Long Belled Piers Differential Settlement

43 Concrete Structures Crowne Plaza Shear Failure of Short Fixed-Fixed Columns

44 Base-Isolated Hospital 7 Story No Damage

45 Snapshot of Structural Performance As of March 24 th, Total commercial and residential buildings within the CBD: 4348 Buildings Inspected 1072 Red Tagged (25%) 1015 Yellow Tagged (25%) 2261 Green Tagged (50%) Heritage Buildings 1084 inspected, 391 Red Tagged (40%) Residential Buildings in Greater Christchurch area: Approx 70,000 inspected 1854 Red-Tagged (2.5%)

46 Rock Falls Nigel s House

47 Rock Falls For sale 1 owner tonne landscape feature (answers to the name Rocky.) He is in pristine condition (just a little bit of concrete dust). Suitable for garden feature, or as in our case a magnificent addition to your living area. Rocky will enhance your "indoor outdoor" flow considerably, especially if you load him in through the garage roof like we did.

48 Art Gallery Glass Facade Good performance Headquarters for Building Assessments