Recent analysis of satellite data shows that the Japan Alps are sinking up to 5 mm per year, according to government geographers.

It is unclear whether the sinking has been happening over a short time or caused by crustal changes, the researchers at the Land, Infrastructure and Transport Ministry's Geographical Survey Institute said.

Theoretically, the mountain range should be rising because it is being squeezed by crustal movements from both the east and west, they said.