Earthquake Hazard and Preparedness In British Columbia Maiclaire Bolton Emergency Management Analyst – Seismic Hazards Maiclaire.Bolton@gov.bc.ca 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

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.

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

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 M7.3 1946 event near Courtenay 2. Deep earthquakes in the subducting Juan de Fuca plate - An example is the M6.8 2001 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 M9 1700 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: 300-800 years Shaking: Strongest (because close to surface) Duration: approx 30-45 seconds (for M7.5) Aftershocks: yes Shaking: Slightly less (shaking weakened because of depth) Duration: approx 10- 15 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

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

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)

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.

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.

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)

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)

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)

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

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

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

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

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

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

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

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

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

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

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

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

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

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.