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Our understanding of earthquakes
in Alaska extends back only to 1788, and studies of ancient earthquakes
can give a better understanding of where they occur, how often they
occur, and how large they are. Studies of young marine and river sediment
layers, buried forests, and soils record subsidence and uplift related
to major earthquakes. Past tsunamis sometimes leave recognizable sand
deposits. In certain cases tree rings can be used to estimate when an
ancient earthquake occurred. Carbon 14 dating of sedimentary layers
offset by young faults can help determine when ancient earthquakes occurred.
The oral history of Native peoples includes legends and stories that
may relate to prehistoric earthquakes.
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In Alaska, paleoseismology
indicates there was at least one other huge earthquake like the one in
1964, 600 to 800 years ago. Some people may conclude that because there
was a major earthquake just 30 years ago that there is little or no earthquake
hazard in parts of southern Alaska for another several hundred years.
However, large earthquakes, on the order of magnitude 8, occur much more
often and can be extremely devastating if they are close to population
centers. |
