Paleoseismological study of the Kizugawa fault system

Authors: Yoshihiko Kariya, Yuichiro Fusejima, Yoshinori Miyachi, Kiyohide Mizuno, Kenji Satake, Akira Sangawa and Ryusuke Imura(Kagoshima Univ.)

Abstract: From numerous historical documents, it has been suggested that the active Kizugawa fault system in western Mie Prefecture is responsible to the 1854 Kaei-Ansei Iga earthquake (M=7 1/4±1/4). However, no geologica
l attempt to verify this idea has been made. Our paleoseismological study comprising field survey, trenching, drilling, and dating techniques has revealed the recent behavior of the fault system as follows: 1) the most recent rupture on the geometrical eastern segment of this fault system took place after the late 16th century, and it certainly corresponds to the 1854 earthquake; 2) vertical and strike components of the slip during the latest event are estimated to be about 2.2-2.6 m and more than 1.2m, respectively; 3) the penultimate rupture of the eastern segment transpired before 1180
cal y BP and may have occurred before 2300 cal y BP; 4) the recurrence interval between the last and penultimate events may be longer than 2000 y; and 5) average vertical slip rate of the fault system is estimated at 0.13 to 0.6 m/ky. The recent rupturing history of the western segment, in turn, is still a matter to be solved.

Sketches of the Higashi-Takakura trench.

Index map