FIGURE 1.1 Global map of active volcanoes and plate tectonics illustrating the “Ring of Fire” and depicting subduction zones; both areas associated with frequent seismic activity. SOURCE: http://vulcan.wr.usgs.gov/Imgs/Gif/PlateTectonics/Maps/map_plate_tectonics_world_bw.gif; USGS.

FIGURE 1.1 Global map of active volcanoes and plate tectonics illustrating the “Ring of Fire” and depicting subduction zones; both areas associated with frequent seismic activity. SOURCE: http://vulcan.wr.usgs.gov/Imgs/Gif/PlateTectonics/Maps/map_plate_tectonics_world_bw.gif; USGS.

that make them vulnerable to future tsunamis. With a clear understanding of the tsunami hazards and social vulnerability that comprise tsunami risk, officials and the general public can then prepare for future events and hopefully reduce this risk.2

When assessing tsunami hazard and developing risk reduction measures, it is important to consider the distance between a coastal community and potential tsunami sources as well as the probability of occurrence. Near-field tsunamis (see Box 1.1) pose a greater threat to human life than far-field tsunamis because of the short time between generation and flooding; because the extent of flooding is likely greater; and because the flooded area may be reeling from an earthquake (National Science and Technology Council, 2005). Near-field tsunamis account for most U.S. tsunami deaths outside of Hawaii, but even Hawaii has suffered losses from near-field tsunamis. Because it takes a very large earthquake to impact the far-field, more triggering events have the potential to impact communities that are within an hour or less from the source. For example, an earthquake generated within the Cascadia fault zone along the northern California, Oregon, and Washington coasts will allow only minutes for evacuation of

2

Risk is a concept used to give meaning to things, forces, or circumstances that pose danger to people or what they value. Risk descriptions are typically stated in terms of the likelihood of harm or loss of a vulnerable thing or process (e.g., health of human beings or an ecosystem, personal property, quality of life, ability to carry on an economic activity) due to a physical event (i.e., hazard).



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