Earthquake effects can include strong ground shaking, ground failure (soil sinking), landslides, tsunamis (tidal waves) and aftershocks. Buildings and other structures may collapse or be severely damaged. Most injuries from earthquakes occur due to falling objects in the home and from building debris from damaged building, as well as, from fires that start in damaged buildings.
The intensity of shaking at a given location depends upon the magnitude of the quake, the distance from the focus and the type of soil. Because of these factors, the damage caused by a quake will vary from one area to another.
Earthquakes are most destructive when they are located near densely inhabited areas. Since about 70 % of the British Columbia population lives in earthquake prone southwestern B.C., there is an obvious need for emergency planning.
If you are near the source of an earthquake, expect a loud bang followed by shaking. If you are farther away, the first warning may be a sudden noise, roar or swaying of the building you are in. Next, you will feel shaking, quickly followed by a rolling motion that rotates up, down and sideways. A moderate earthquake may last only a few seconds. A large earthquake could last several minutes.
An earthquake does not always cause the earth to split open and swallow up people and neighbourhoods. Buildings do not automatically collapse, either. However, you could be hurt by shattered glass, falling objects and heavy objects thrown around by the shaking. Broken gas mains and fallen chimneys can cause fires. Downed power lines and broken water mains can also wreak havoc.
Aftershocks are smaller earthquakes that happen when the earth underneath the surface adjusts to a new position. Aftershocks may happen for some time after the initial earthquake, Over time, they generally grow weaker.
A tsunami is a series of traveling waves generated by an earthquake below the ocean floor. The wave may have sufficient energy to travel across entire oceans. Tsunamis steepen and increase in height on approaching shallow water and can surge over low-lying coastal areas, causing severe damage.
Although ground shaking is the major cause of earthquake damage, landslides, the liquefaction of saturated soils, flooding, and tsunamis can also cause loss of life and massive destruction to property and the environment.
In recent years, large buildings, roadways and other infrastructures have been built on reclaimed land, steep slopes and unstable soils. Such areas are at high risk of being damaged by a large earthquake. This also means that in future, earthquakes in such built-up areas could affect more people and cause more damage than in the past.