Tsunamis, Types of
Tsunamis, Types of : A zone of extreme seismic activity circles the Pacific Basin from the southernmost reaches of Chile to Alaska in the eastern part of the basin, and from New Zealand through to Japan and the Aleutian Islands in the western part of the basin. This "Ring of Fire," as it has been named by scientists, periodically generates earthquakes that produce large ocean waves called tsunamis that may threaten island and coastal settlements. Tsunamis are a rare but serious threat. Three main types of tsunamis could impact B.C.'s coast: Pacific-wide Tsunami: A Pacific-wide tsunami originates in a location other than coastal North America. The impact to British Columbia will depend on the source distance, magnitude and direction of approach. B.C. arrival times of a Pacific-wide tsunami will be 6 hours to 18 hours, depending upon the place of origin and magnitude. Regional Tsunami: A regional tsunami originates off coastal North America including the area from the Aleutian Islands or to southern California, excluding the Cascadia subduction zone. Alaska, including the Aleutian Islands, is the principle source area for regional tsunamis affecting B.C. The time to reach the northern B.C. coast can be less than one hour or as many as 5 hours. In 1964 a regional tsunami impacted the B.C. coast, causing significant damage to several communities. Local Tsunami: A local tsunami will be generated from a large subduction earthquake along the Cascadia subduction zone. For this event, Zone C (exposed west coast) would be the most affected area in B.C. There is also potential for a local tsunami to be generated from earthquakes occurring in inner waters such as Juan de Fuca Strait, the Strait of Georgia or Puget Sound, or from submarine slides in areas such as the Strait of Georgia. Because travel time for any local tsunami is so short, very little can be done to provide warnings for the closest B.C. coastal areas. In designated coastal areas, anyone in coastal locations who feels strong shaking from an earthquake for more than one minute should assume that a tsunami has been generated and should immediately move to high ground
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