Emergency Perparedness and Planning
Fire Safety Plans
- is a working document for SD 64 staff, students and parents.
- by the Saltspring Fire Department.
British Columbia experiences over 1,200 earthquakes a year, 300 of which occur in the lower mainland and on Vancouver island. Almost all of these earthquakes are too small to be felt. However, a stronger earthquake could occur at any time. It may happen during the day or at night, on a weekend or a workday, in any season and in any weather condition.
British Columbia is vulnerable to two types of earthquakes: those occurring within the earth’s crustal plates and those occurring at the interface between crustal plates. Earthquakes that originate within a plate are seldom greater than magnitude 7.5 and typically shake for less than one minute. In contrast, earthquakes that originate between plates are usually larger than magnitude 8.0 and the shaking may last as long as 3 or 4 minutes.
British Columbia is vulnerable to the largest type of earthquake called a “subduction” quake, which occurs between two plates. The Cascadia Subduction Zone is located approximately 100 kilometers west of Vancouver Island and earthquakes here recur every 550 years on average. The range of recurrence, however, varies from 200 years to 900 years. The last subduction earthquake was in January 1700.
The most powerful earthquake ever recorded in Canada is a magnitude 8.1 earthquake in the Queen Charlotte Islands—and the largest earthquake likely to have occurred in Canada is the 1700 Cascadia Earthquake with an estimated magnitude of 9.0.
What’s the largest earthquake possible?
The largest earthquakes recorded on earth are subduction earthquakes– measuring magnitude 9.5 off the coast of Chile in 1960 and magnitude 9.2 in Alaska in 1964. Generally the size of an earthquake is controlled by the length of the faults on which they occur. The longer the fault—the stronger the potential earthquake. Currently, there are no known faults capable of generating a magnitude 10.0 or larger earthquake.