Itoigawa-Shizuoka Tectonic Line

The Itoigawa-Shizuoka Tectonic Line is a major tectonic boundary in central Japan, extending from Itoigawa to Shizuoka and marking the western edge of the Fossa Magna.

Fossa Magna: A broad tectonic depression in central Honshu, filled with younger volcanic and sedimentary rocks. The tectonic line forms this region’s western boundary.
Pacific Plate: A large oceanic tectonic plate underlying much of the Pacific Ocean. Its motion toward Japan contributes to deformation across the archipelago.
Japanese Alps: A group of mountain ranges in central Honshu, including the Hida, Kiso, and Akaishi ranges. Their uplift and deformation are closely tied to central Japan’s tectonic framework.
Active fault: A fault that has moved in the geologically recent past and may move again. The line’s mapped fault segments are evaluated as active earthquake sources.
Sakhalin-Hokkaido Shear Zone: A zone of crustal deformation extending through Sakhalin and Hokkaido in northeastern Asia. It is a major northern deformation zone, unlike this boundary in central Honshu.
Itoigawa-Shizuoka Tectonic Line fault zone: A system of active faults associated with the Itoigawa-Shizuoka Tectonic Line. This fault system accommodates deformation along the boundary.
Philippine Sea Plate: An oceanic tectonic plate subducting beneath parts of southwest and central Japan. Its interaction with nearby plates helps complicate central Japan’s tectonics.
Hida Mountains: A mountain range in central Honshu, also known as the Northern Japanese Alps. The range lies west of the Fossa Magna and exposes older crustal rocks.
Seismic hazard: The likelihood and severity of earthquake ground shaking at a location over a stated period. Fault activity along the line contributes to hazard estimates in central Japan.
Japan Trench subduction zone: The plate-boundary zone where the Pacific Plate descends beneath the Okhotsk Plate east of Japan. This is an offshore subduction boundary, whereas the tectonic line is an inland crustal boundary.

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