Itoigawa-Shizuoka Tectonic Line

Itoigawa-Shizuoka Tectonic Line (ISTL) (糸魚川静岡構造線), also Ito Shizu Sen (糸静線) is a major fault zone on Honshu island running from Itoigawa, Niigata Prefecture, through Lake Suwa, and on to Shizuoka in Shizuoka Prefecture. It is often confused with the Fossa Magna ("great rift"), a geological feature it forms the western boundary of.

Seismic activity
Recent significant earthquakes on this tectonic line include:
 * M5.4; 30 June 2011; epicentre near Matsumoto, Nagano; 1 death, 17 injuries.
 * M6.7; 22 November 2014; epicentre near Hakuba, Nagano; 46 injuries.