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Cryoseisms (or frost quakes) in Maine
A cryoseism, or frost quake, is a natural phenomenon that produces ground shaking and noises similar to an earthquake, but is caused by sudden deep freezing of the ground. They typically occur in the first cold snap of the year when temperatures drop from above freezing to below zero, particularly if there is no snow cover to insulate the ground. The primary way that they are recognized is that, in contrast to an earthquake, the effects of a cryoseism are very localized. In some cases, people in houses a few hundred yards away do not notice anything. The reason that the vibrations do not travel very far is that cryoseisms don't release much energy compared with a true earthquake caused by dislocation of rock within the earth. On the other hand, since cryoseisms occur at the ground surface they can cause significant effects right at the site, enough to jar people awake. Cryoseisms typically occur between midnight and dawn, during the coldest part of the night. If conditions are right, they may occur in a series of booms and shakes over a few hours or even on successive nights.
There have been a few cases reported in the northeastern U.S. where people have been able to find a small crack in the ground where the cryoseism occurred. In these particular cases, it appears that the cracks are caused by the ground having contracted rapidly due to the sudden cold, and split apart - a literal "cold snap"! Unfortunately, that sort of evidence can be difficult to find because the cracks are quite small, they might be some distance away from where it was felt, and are liable to be covered by snow and healed by the spring thaw before anybody would notice them.
Due to their haphazard occurrence and the generally minor effects, there is not much scientific data about cryoseisms, but it seems that the particular combination of weather conditions is more important than the type of geology or soils in determining where they occur. Cryoseisms have been reported from upstate New York, Vermont, Massachusetts, Connecticut, and Maine.
List of recent Maine events that might have been cryoseisms.
Lacroix, Andrew V., 1980, A short note on cryoseisms. Earthquake Notes, vol. 51, no. 1, pp. 15-20.
Last updated on October 6, 2005