Geoscience Reference
In-Depth Information
bitmap
FIGURE 1.1
Global map of active volcanoes and plate tectonics illustrating the “Ring of Fire” and depict-
ing 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, oficials 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-ield tsunamis (see Box 1.1) pose a greater threat to
human life than far-ield tsunamis because of the short time between generation and looding;
because the extent of looding is likely greater; and because the looded area may be reeling
from an earthquake (National Science and Technology Council, 2005). Near-ield tsunamis ac-
count for most U.S. tsunami deaths outside of Hawaii, but even Hawaii has suffered losses from
near-ield tsunamis. Because it takes a very large earthquake to impact the far-ield, more trig-
gering 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).
