| Itoigawa-Shizuoka Tectonic Line | |
|---|---|
 The blue line represents the fault, with the Fossa Magna shaded in orange. The red line indicates Median Tectonic Line. | |
| Country | Japan |
| Characteristics | |
| Segments | multiple |
| Tectonics | |
| Status | Active |
| Earthquakes | Tectonic |
| Age | Miocene-Holocene |
| Japanese Active Fault database or search | |
Itoigawa-Shizuoka Tectonic Line (ISTL) (糸魚川静岡構造線, Itoigawa Shizuoka Kōzō Sen), 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.