1. Earthquake Hazard and Preparedness In British Columbia
Maiclaire Bolton
Emergency Management Analyst – Seismic Hazards
I will give a brief overview of the earthquake threat in BC and a little bit about how you can prepare.
JIIRP Workshop
February 26, 2007

2. Is there an Earthquake Threat in BC?
YES!
So, first off – Is there a threat of earthquakes in BC?
The answer is clearly, YES.
Here we have a map of earthquake on the west coast and we can see that BC is very seismically active.
70% of BC’s population is in an earthquake zone.

3. History of Damaging earthquakes in BC
The biggest earthquakes in BC were:
1700: W of Van. Island (M9)
1872: S. of Hope (M7.4)
1918: W. Van. Island (M7.0)
1946: W of Courtenay (M7.3)
1949: Queen Charlottes (M8.1)
We have a history of damaging earthquakes in BC. We have about one damaging earthquake in BC every decade or so.
Here I’ve listed the largest earthquakes BC has experienced, all greater than M7.
The 1946 event was the last significant damaging event recorded in BC

4. Why do they occur? North America Plate EQs (1946) Shallow Juan de Fuca
(2001)
Subduction Zone
EQs (1700)
The Big One
Deep
Shallow
So why do we get earthquakes here?
-This is the Cascadia Subduction zone and here we see this in cross section
-the Cascadia Subduction zone with marks the interface of the Juan de Fuca and North America plates.
The seismicity in our region results from the interaction of these plates.
Shallow earthquakes in the North America plate
- An example of this is the M event near Courtenay
2. Deep earthquakes in the subducting Juan de Fuca plate
- An example is the M Nisqually earthquake near Olympia, Washington that was felt here in Victoria.
3. Large Subduction zone earthquake that occur along the interface of the two plates.
An example of this is the M Cascadia earthquake
North America Plate (shallow)
Maximum Magnitude: approx Magnitude 7.5
Last major event: 1946
Recurrence: approx one every decade
Juan de Fuca Plate (deep)
Maximum Magnitude: approx Magnitude 7.0
Last major event: 2001
Cascadia Subduction Zone (big one)
Maximum Magnitude: approx Magnitude 9
Last major event: 1700
Recurrence: years
Shaking: Strongest (because close to surface)
Duration: approx seconds (for M7.5)
Aftershocks: yes
Shaking: Slightly less (shaking weakened because of depth)
Duration: approx seconds (for M7.0)
Aftershocks: not as likely
Shaking: Severe shaking over a wide area
(most severe shaking is away from major centres)
Duration: approx 3-4 minutes

5. Earthquake Effects
The Primary effect is strong ground motion – shaking and rolling...
The primary effect from an earthquake is strong ground motion - first shaking, followed by rolling.
Here are some damage photos
On the Left: Izmit, Turkey, 1999, M7.4
Top Right: Olympia, WA, 2001, M6.8
Bottom Right: California, 1994 M6.7
The Obvious impacts are on buildings and houses…
but also on…
bridges, railways, airport runways
powerlines,
gas lines,
water lines,
phone lines
Earthquakes are very destructive.
Olympia, WA
2001
Izmit, Turkey, 1999
Northridge, CA
1994

6. Secondary Earthquake Effects
Liquefaction…
Now, ground motion is the primary effect from earthquakes, but there are several other effects that I term “secondary effects” and I want to talk about these now.
First of all – Liquefaction.
This is when earthquake shaking causes soils to lose their strength and become somewhat like a liquid and structures lose their foundations.
Liquefaction is commonly one of the major causes of damage in an earthquake.
From these pictures you can see that even strong structures are susceptible.
One of the highest liquefaction hazard areas in the Province is Richmond (and any area in the river delta)
Kocaeli, Turkey (1995)
Nigata, Japan (1964)

7. Secondary Earthquake Effects
Landslides…
“Landslides” – and this includes: rockslides, rockfalls, debris slides, debris torrents, land slumps, topples and falls, and land slides
Landslides cause direct damage to homes, utilities, infrastructure..
But also indirectly is a major consequence as they can block or destroy paths to response.
In this photo buildings have become buried
Kobe (1995)
U.C.Davis; Virginia Tech.

8. Secondary Earthquake Effects
Subsidence…
Subsidence – which is when the ground drops suddenly because of an earthquake.
Because of built up stress, the west coast is expected to subside about 1 meter in the next Cascadia Subduction zone earthquake.
And I have a diagram to explain this a little bit better….
Kocaeli, Turkey (1995)
U.C.Davis; Virginia Tech.

9. Secondary Earthquake Effects
Flooding...
Chi Chi, Taiwan (1999)
Flooding –
Flooding can be caused by:
Broken dams
Landslides blocking rivers, impounding water
Broken water mains
Blocked or ruptured storm drains.
The pictures are:
Top - flooding from a broken dam in Taiwan
Bottom – Dyke breach in Loma Prieta in California
Loma Prieta, CA (1989)

10. Secondary Earthquake Effects
Fires...
Fire can be very destructive
These photos are from the M7.4 earthquake in Turkey.
Another example is the 1906 San Francisco earthquake where the almost the entire city was destroyed by fire.
Izmit, Turkey (1999)

11. Secondary Earthquake Effects
Tsunamis...
Anchorage, AK (1964)
And last, but certainly not least is tsunamis.
These pictures show the destruction from the tsunami following the 1964 M9.2 earthquake in Alaska.
Port Alberni, BC (1964)

12. Earthquake Preparedness
Before an Earthquake
Develop a plan
Prepare an emergency kit (home, work, vehicle)
Mitigate damage to your home
Plan to be self-sufficient for at least 72 hours
-Develop plan
-prepare an emergency kit (for home, work, and vehicle)
-mitigate damage to your home (everything from securing top heavy furniture, fix mirrors and pictures to the walls, bolt house to foundation, and just identifying hazards within your home or office)
-and plan to be self-sufficient for at least 2 hours

13. Earthquake Preparedness
During an Earthquake
Drop, Cover, and Hold.
Remain in a protected place until shaking stops
Generally say, drop, cover and hold and remain there and count to 60 after the shaking stops

14. Earthquake Preparedness
After an Earthquake
Stay calm
prevent further injury
hang up phones
get earthquake kit
check for hazards,
check for building damage
expect aftershocks
stay calm
prevent further injury
hang up phones,
get earthquake kit - Help yourself first, then others,
check for hazards - fire, gas, electrical,
check for building damage,
expect aftershocks

16. Earthquake Damage… What can we expect?
Now, in BC we haven’t experiences a major destructive earthquake in modern times, but we know it can and will happen so we need to know what to expect

17. Chimney Failure Vancouver Island 1946 (M7.3) Courtenay Elementary
School
This is damage to the Courtenay Elementary School in the 1946 M7.3 earthquake
Chimney damage is very common because they’re made of brick, not supported, and they stick out (no diagonal or horizontal bracing), …
Vancouver Island 1946 (M7.3)
GSC

18. URM Wall Collapse Loma Prieta 1989 (M7.2) FEMA
Another common type of earthquake damage is to Unreinforced Masonry (or URM) Buildings.
This is a URM wall collapse in the Loma Prieta earthquake
Loma Prieta 1989 (M7.2)
FEMA

19. URM Collapse Nisqually 2001 (M6.8) Seattle Times
And a URM collapse from the 2001 Nisqually earthquake.
We have a lot of buildings like this in BC and I wouldn’t want to point fingers at any of them in particular, but a example of this kind of building is a famous historic hotel in downtown Victoria – it likely wont fair very well
Nisqually 2001 (M6.8)
Seattle Times

20. Soft Storey Failure Loma Prieta 1989 (M7.2) FEMA
Another type of common damage is soft storey failure.
Soft storey is a “relatively stiff structure, with a flexible first storey” , so anything with an open ground storey (ie with garage on the bottom, held up only with pillars.
There are several buildings in downtown Victoria and Vancouver that are …… *****?????? (open space on the first storey)
Loma Prieta 1989 (M7.2)
FEMA

21. Soft Storey Failure Loma Prieta 1989 (M7.2) FEMA
Another example – this one had a garage on the ground floor.
Loma Prieta 1989 (M7.2)
FEMA

22. Building Collapse Morocco 1960 (M6.7) FEMA
This picture astonishes me every time I see it. This was a hotel…
Here you have the building before and it was absolutely destroyed by a M6.7 earthquake in Morocco
Morocco 1960 (M6.7)
FEMA

23. Pancaking (13 storey URC)
This is an example of pancaking from the M 8.1 Mexico City earthquake
This was 13 storeys of unreinforced concrete
Mexico City 1985 (M8.1)
FEMA

24. Freeway Collapse Loma Prieta 1989 (M7.2) FEMA
And we all know that it’s not just buildings at risk, but also critical infrastructure
This was a freeway collapse in the Loma Prieta earthquake
Loma Prieta 1989 (M7.2)
FEMA

25. Freeway Collapse Kobe 1995 (M6.9) FEMA And one from Kobe, Japan
We have several overpasses in BC – try to think about the consequences from one of them collapsing.
Kobe 1995 (M6.9)
FEMA

26. Dam Failure Chi-chi (Taiwan) 1999 (M7.6) U.C.Davis; Virginia Tech.
The collapse of a dam in the M7.6 ChiChi earthquake in Taiwan.
We have a lot of dams in BC….
Chi-chi (Taiwan) 1999 (M7.6)
U.C.Davis; Virginia Tech.