The ground has been shaking and cracking recently in Oulu. The warm and rainy autumn quickly followed by the present extremely cold temperatures has resulted in extensive freezing and cracking in the ground.
The frost quakes may often result in damaging cracks in road surfaces or depressions in yards. More serious damage has never been reported.
Shaking typically occurs at sunset, although sunrise quakes are not uncommon. Changes in temperature are most rapid at those times, and drastic changes in the composition of frozen masses in the ground are most likely to occur then.
The effects of a frost quake are relatively strong because they occur near the surface, but the quakes generally dissipate quickly. Ice cracking on lakes in the wintertime is the most common example of a frost quake.