Major Japanese nonlife insurers have started revising earthquake insurance premiums by reassessing damage risks region by region.

Next January, Tokio Marine & Nichido Fire Insurance will raise premiums for areas including the Shikoku region that could suffer damage from an expected powerful earthquake occurring along the Nankai Trough off the Pacific coast of central Japan, and from subsequent tsunami, reported The Japan Times.

The insurer is also reviewing risks associated with a possible major earthquake that could happen in the Sagami Trough, which lies in the Pacific Ocean off Kanagawa Prefecture. It will increase premiums for Tokushima, Kochi, Ehime, Wakayama and Ibaraki prefectures by up to about 50%, depending on building structure.

Premiums will also be raised for Shizuoka and Kagawa prefectures but will be lowered for many places in the Tohoku, Hokuriku, Chugoku and Kyushu regions.

The insurer will keep premiums unchanged for Osaka Prefecture and Tokyo.

The company’s average quake insurance premium rate across the country will remain almost the same as the level before the review.

Among other insurers, Sompo Japan Nipponkoa Insurance revised its area classification for deciding premium levels in February this year.

Instead of the conventional prefecture-by-prefecture classification, the unit of Sompo Holdings subdivided the country’s 47 prefectures into 948 areas based on postal codes. The company raised premiums for coastal areas that are vulnerable to tsunami and lowered the rates for inland areas.