Case Study: Along the Cascadia Subduction Zone

Looking at the geology of where Vancouver is and what lies near and beneath its surface, one can understand why Vancouver is at such high risk for earthquakes. There are plates subducting below the less dense, North American plate which is descending below the continental plate at a rate of 45 mm/year. Subduction occurs along the Cascadia subduction zone. This is the second largest tectonically active fault system in North America. The subduction zone has ruptured several times over history, causing great earthquakes. Much of the force that leads the oceanic plates to subduct beneath the North American plate is generated by a ridge system. The largest ridge in Vancouver is the Juan de Fuca ridge. Grinding of the plates as it moves along the aforementioned faults generates stress. Plate interaction along any of the convergent, divergent, or transform faults may cause the buildup of stress which will lead to an earthquake. With the evidence of past earthquakes we know a major one will occur in the area along the Cascadia subduction zone at any time. The geological setting makes this densely populated region susceptible to frequent seismic activity.  Vancouver has an increased risk of disastrous megathrust earthquakes, the region is surrounded by the Coast Mountains and the Pacific Ocean making it isolated and vulnerable during a large earthquake.

Liquefaction : Is a phenomenon in which the strength and stiffness of soil is reduced by earthquake shaking. This is a hazard because when it occurs, the strength of the soil decreases and the ability of soil deposit to support foundations for buildings and bridges is reduced. It can be responsible for a tremendous amount of damage and a hazard for many lives.

Landslides : Is the movement of rock, debris or earth down a slope. They result from the failure of the materials which make up the hill slope and are driven by the force of gravity. Sudden and rapid  events are most dangerous because of the lack of warning and the speed at which material can travel down the slope, also the force on the resulting impact. Extremely slow landslides may not be a threat to people but it can cause considerable damage to property. There are many resources that could be ruined, for example water supplies, fisheries, and roads. Landslides can cause massive destruction which will impact the economy as for all of the repair.

Tsunami : Are giant waves caused by earthquakes or volcanic eruptions under the sea. A the waves travel inland, they build up to higher and higher heights as he depth of the ocean decreases. The speed of tsunmai waves depends on ocean depth rather than distance from the source of the wave. In some cases they can result in floods reaching up to 100 feet in height. They can cause a lot of property damage, environmental damage and leaving many lives at risk.

Flooding : Is a natural event where an area that is dry land, suddenly gets submerged under water, Floods that happen in areas where people live in, the water carries along the objects such as houses, bridges, cars, furniture, and even people. It can wipe away farms and trees as well.

Social Impact : Earthquake hazards pose serious intermediate term risk to health and safety and economic viability. They demonstrate risks to industrial societies from the event, affecting everything from massive loss of life, infrastructure damage and financial instability. Earthquakes can have short term and long term impacts. Short terms would include people being injured, destroyed homes, disruption to transportation and communication. Long term impacts would include a disease being spread and peopling having to re-house.

Economic Impact : Earthquakes can result in massive destruction of roads, bridges, farms, houses, automobiles and people become homeless. The government deploys fireman, police and other emergency apparatuses to help the affected. Everything comes at a heavy cost to the people and the government. It takes years for affected communities to be re-built and businesses to come back to normal.

Infrastructure Impacts : Earthquakes can effect availability of many services and elements of infrastructure. The large and violent movement of the ground caused by an earthquake will disrupt many services. Electric line poles are vulnerable to damage. No electricity results in no light, heat and no water. Land-line phones will not have service as the towers may be damaged. Natural gas pipelines could also be broken. Almost all stores rely on supplies being brought by trucks, so supply lines will be impacted. Local airports and train facilities can also be damaged. Bridges, buildings, and hospitals can be destroyed or damaged causing a great effect.

Preparedness: Communities in Metro Vancouver are preparing for the impending earthquake by making a significant investment to assess earthquake risk, upgrade infrastructure and develop emergency plans. The city has developed the Earthquake Preparedness Strategy to reduce the impact of an earthquake in Vancouver. The strategies fall under four categories; earthquake risk assessment, earthquake risk reduction, earthquake preparedness and earthquake response and recovery. Families have made small changes in there homes for their safety as well. For example storing food and water, having an identified family meeting location, have an emergency prepared plan and kit, buying self powered radios and flashlights, hanging pictures and home decor away from where people may sit, and by simply placing heavy objects on lower shelves.