November 23, Earthquake Research Committee of the Japanese government announced a provisional assessment of the earthquake that occurred in Nagano Prefecture, on the 22nd.Committee has pointed out the possibility of "Itoigawa-Shizuoka Tectonic Line" was the cause.
According to the committee, this earthquake may have been caused by Kamishiro fault. This fault is part of the "Itoigawa-Shizuoka Tectonic Line". This region has been pointed out that there is a risk of a major earthquake.
Itoigawa Shizuoka line is across the Japanese archipelago center from north to south. Some of the mountains are lined up along this line. Its surroundings are areas where a lot of faults exist.Experts have noted that it is necessary to investigate and study about them.