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A cryoseism, also known as an ice quake or a frost quake, is a seismic event that may be caused by a sudden cracking action in frozen soil or rock saturated with water or ice. As water drains into ground, it may eventually freeze and expand under colder temperatures, putting stress on its surroundings. This stress builds up until relieved explosively in the form of a cryoseism. Another type of cryoseism is a non-tectonic seismic event caused by sudden glacial movements. This movement has been attributed to a veneer of water which may pool underneath a glacier sourced from surface ice melt. Hydraulic pressure of the liquid can act as a lubricant, allowing the glacier to suddenly shift position. This type of cryoseism can be very brief, or may last for several minutes. The requirements for a cryoseism to occur are numerous; therefore, accurate predictions are not entirely possible and may constitute a factor in structural design and engineering when constructing in an area historically known for such events.〔 Speculation has been made between global warming and the frequency of cryoseisms.〔 == Effects == Cryoseisms are often mistaken for minor intraplate earthquakes.〔 Initial indications may appear similar to those of an earthquake with tremors, vibrations, ground cracking and related noises,〔 such as thundering or booming sounds.〔 Cryoseisms can however be distinguished from earthquakes through meteorological and geological conditions.〔 Cryoseisms can have an intensity of up to VI on the Modified Mercalli Scale.〔 Furthermore, cryoseisms often exhibit high intensity in a very localized area,〔 in the immediate proximity of the epicenter,〔 as compared to the widespread effects of an earthquake.〔 Due to lower-frequency vibrations of cryoseisms,〔 some seismic monitoring stations may not record their occurrence.〔 Although cryoseisms release less energy than most tectonic events, they can still cause damage or significant changes to an affected area.〔 Some reports have indicated the presence of "distant flashing lights" before or during a cryoseism, possibly due to electrical changes when rocks are compressed.〔 Cracks and fissures may also appear as surface areas contract and split apart from the cold.〔〔 These sometime superficial to moderate occurrences may range from a few centimetres to several kilometres long, with either singular or multiple linear fracturing and vertical or lateral displacement possible.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cryoseism」の詳細全文を読む スポンサード リンク
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