The vertical slip-rate and geomorphological mapping between Tsugaike and Lake Kizaki along the northern Itoigawa-Shizuoka tectonic line active fault system

Abstract

The Itoigawa-Shizuoka tectonic line (ISTL) is one of the major tectonic lines in Honshu Island, Japan, and its northern and central part forms an active fault system. As the slip-rates of active faults provide the basic information for understanding quantitative active tectonics, we estimated the slip-rates along the northern part of ISTL active fault system by tectonic geomorphological study and the aerial photogrammetric survey. We took large-scale air photographs along ISTL. When tectonic landforms were artificially modified, we measured terrace offsets using old air photographs. We described the geomorphological interpretation of deformed landforms in this paper and precisely mapped fault traces. As a result, vertical slip rates of the ISTL active fault system in this area except the northern edge have no significant changes. In the northern edge, the vertical slip rate of the east dipping fault is on the decrease, and that of the west dipping fault is on the increase. Consequently, we inferred that the west-dipping fault began activation instead of the east dipping fault.