Earthquakes of Southwest British Columbia: Past, Present, and Future.

Transcription

1 Earthquakes of Southwest British Columbia: Past, Present, and Future. John F. Cassidy Natural Resources Canada, Sidney, BC Delta Neighbourhood Emergency Preparedness Program November 28, 2011.

2 Talk Outline Earthquakes an Introduction Earthquake History of BC Earthquake Research - minimising the impact. Recent Global Earthquakes lessons learned.

3 3 Plate Tectonics We are here!

4 4 Earthquakes of the World R. Kung

5 5 Storing (and Releasing) Energy San Andreas Fault 1906 USGS (photo by Gilbert)

6 6 Earthquake Rupture Movement along a fault can cause displacements Earthquake waves radiate out from the rupture zone (Focus)

7 Magnitude Magnitude as magnitude increases, the strength of ground shaking, duration, and area impacted increases very quickly. ground shaking Increases by 10 times for every magnitude unit Energy released Increases by 32 times for every magnitude unit duration of shaking From a few seconds (M 4) to several minutes (M 9)

8 8 Earthquake History Earthquakes are a part of life on the west coast Small earthquakes everyday! Damaging earthquakes (decades apart) World s largest earthquakes (centuries apart) Kwakiutl Earthquake Mask UBC, Museum of Anthropology

9 9 Small Earthquakes (everyday)! 129 earthquakes during the past 30 days.

10 10 Large Earthquakes (decades apart)!

11 11 Huge Earthquakes! (centuries apart) M 8.2 M 8.1 M 9.0

12 12 West Coast Tectonics

13 13 Three Types of Earthquakes

14 14 Large Crustal Earthquakes (M 7-7.5): 1872, 1918, 1946

15 Vancouver Island M=7.3

16 damage unreinforced masonry

17 damage: Landslides / soil failure

18 damage: Chimney / foundation damage

19 earthquake: landslides Landslide Lake (west of Mt. Washington) Formed by landslide from 1946 earthquake. 1.5 million m 3 rock!

20 20 Deep Earthquakes (M=6.5-7): 1949, 1965, 2001 Few or no aftershocks!

21 21 Nisqually earthquake damage: $2 billion Seattle Times

22 22 Non-structural damage Watch for falling or flying items!

23 23 Megathrust Earthquakes (M 9) (like 2004 Sumatra)

24 24 GPS Data: long-term crustal motions Daily positions of UCLU and CHWK wrt DRAO (Penticton) for Dragert, Schmidt

25 25 Subduction Fault - Locked (storing energy)

26 26 Subduction Fault Slipping (releasing energy)

27 27 Subsidence and tsunami deposits Subsidence along the coast 13 events during past 6000 years ~500 years between deposits (range of about years) John Clague, Brian Atwater

28 28 Megathrust Effects Shaking for several minutes Aftershocks for months to years Long-period shaking Area impacted from BC to California Tsunami Alaska (1964), Chile (1960)

29 29 January 26, 9 p.m. It was at nighttime that the land shook They had no time to get hold of canoes No time to get awake They sank at once, were all drowned. Not one survived. First Nations legend of winter village near Pachena Bay.

30 30 Tsunami! January 28, 1700 tsunami in Japan Damaged buildings/crops Caused shipwreck in Japan January 26, 1700 at 9 p.m. Pacific Time! K. Satake

31 31 The Cost of Earthquakes Kobe, Japan 1995 M=6.8 $130B+ Seattle 2001 M=6.8 $3.5B Chile 2010 M=8.8 $40B Christchurch 2011 M=6.1 $20B Japan 2011 M=9.0 $300B? The goal of earthquake science and engineering is to minimise the impact of future earthquakes. To save lives, and save money. *Source: Internet

32 32 Earthquake Research, Forecasting, and Warning. How will the ground shake?? How often? Where is energy being stored? Work with engineers to ensure that buildings and structures can withstand this level of shaking

33 33 Earthquake Monitoring

34 34 Mapping Earthquake Hazard: 2005 National Building Code

35 35 Earthquake Research Earthquake Warning??

36 36 Dense Urban Seismic Networks: Now Possible! Low-cost, robust, continuous monitoring

37 37 Dense Seismic Networks: Warning Systems

38 Earthquake Early Warning P S P-waves travel at 6 km/s S-waves travel at 3 km/s Whistler to Vancouver Driving: 90 min. P-wave: 18 sec. S-wave: 32 sec.

39 Earthquake Early Warning Potential Warning Time in Vancouver: 1 Nanaimo: 20 s 2 Offshore: 90 s 3 California: 5 min km away 1

40 40 Dense Seismic Networks: Applications Seconds of warning before strong ground shaking arrives can be used to: stop trains control bridge/tunnel traffic critical facilities (close valves/switches) surgeons (put down the scalpel )

41 learning from Chile

42 Felt area Felt to 3500 km distance! Strong shaking over an area ~ 500 km x 100 km USGS

43 M 8.8 Chile Earthquake - Impacts 523 people killed 12,000 people injured 800,000 people displaced 370,000 homes damaged/destroyed 4013 schools damaged/destroyed 79 hospitals damaged $40 B economic impact

44 Chile Earthquake - Impacts Impacts on Families homes cars jobs or business

45 Chile Earthquake - Impacts Impacts on Communities hospitals schools business transportation Curico Talca

46 Chile Earthquake - Impacts Impacts on Communities hospitals schools business transportation

47 Chile Earthquake - Impacts Impacts on Communities hospitals schools business transportation

48 Recent earthquakes: Building Codes Work Haiti M 7.0 >300,000 deaths Chile M deaths ~ 500 times larger than M 7

49 Chile Earthquake What Worked Building Codes Work! How Modern Buildings Performed: (buildings constructed between 1985 and 2009) No. built with 3 or more stories: 10,000 No. built with 9 or more stories: 2,000 Total Buildings Collapsed = 4 (approx.) Total Buildings Badly Damaged = ( %)

50 Chile Earthquake What Worked Education and Public Awareness!

51 51 Reducing the Risk We are making progress. Seismic retrofits of bridges

52 52 Reducing the Risk We are making progress. Seismic retrofits of schools

53 53 Reducing the Risk We are making progress. Seismic retrofits of older buildings

54 54 Reducing the Risk We are making progress! Greater awareness of earthquakes Personal preparedness

55 55 Summary This is earthquake country!! Be prepared for earthquakes Know what to do before, during, and after an earthquake. ShakeoutBC.ca Pep.bc.ca Getprepared.gc.ca Kwakiutl earthquake mask

56 56 Thank You!

57 57 Soil Effects 10 STOREY 1 STOREY Centre

58 Nisqually Earthquake Recordings Greater Vancouver

59 59 Tsunami hazard

60 Tsunami Model Cherniawsky et al., PAGEOPH, 2006

61 61

62 62 Recommended Tsunami Planning Levels (BC P.E.P. Website) Zone Wave height Run-up (x 2.0) Safety (x 1.5) Subsidence Planning Level Zone A m North Coast Zone B m Central Coast Zone C m W. Coast Van. Is. Zone D m Juan de F. Strait Zone E m Georgia Strait

63 63 Ratio of Tsunami Amplitudes at Victoria and Tofino Observed Modelled HM89 NL92 CW06 Rat ~0.5 Amp m HM89 NL92 CW06 Hebenstreit and Murty, 1989, Marine Geology Ng, Le Blond and Murty, 1992, Natural Hazards Cherniawsky et al., 2006, Pure and Applied Geophysics

64 64 03:34 Feb. 27, 2010 M 8.8 Felt across much of South America. Felt to distances of nearly 3400 km (Peru, Brazil). Maximum intensity of 8 (severe shaking) reported in many coastal communities. USGS

65 65 Aftershocks USGS

66 66 Tsunami Damage - Iloca

67 67 Shaking old buildings Talca, Constitucion, Caquenes, Curico most adobe buildings destroyed

68 68 Shaking wood buildings Curico near collapsed church On the coast- near the rupture

69 69 Soil Failures Lake Vichuquen

70 70 Soil Failures and Highways

71 71 Hospital de Curico

72 72 Lessons Learned: Talca Hospital 2003 Building codes work! 1920 s Last eruption about 7200 years ago

73 73 Lessons Learned: Tsunami s Size doesn t matter a 2 m high tsunami can destroy homes and communities. Education pays! Many thousands of lives were saved in Chile.

74 74 Lessons Learned: Education Education and awareness safes lives!

75 75 Additional Information Earthquake info: Preparedness info: Tsunami info: htm

76 76 Tsunami Risk High Risk: Zone C: West Coast of Vancouver Island Medium Risk: Zone A: North Coast Zone B: Central Coast Low Risk: Zone D: Juan de Fuca Strait Very Low Risk: Zone E: Georgia Strait

77 77 Tremor and Crustal Earthquakes?? Honn Kao

78 78 Leech River Fault