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Trench excavation surveys on the surface ruptures appeared in the Aso caldera associated with the 2016 Kumamoto earthquake

About 3-km-long E-W trending surface ruptures along the south side of the Nigorikawa River, Minamiaso village were observed soon after the 2016 Kumamoto earthquake. Our trench was excavated across two E-W trending traces of surface ruptures appeared in a graben. Inclined strata towards the center of the graben (the front side in the photo) and some normal faults connecting to the surface ruptures were observed in the trench. See detail in Shirahama et al. on pages 161-212.

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Vibro-coring survey at the eastern marginal fault zone of Ishikari lowland off the Yufutsu plain, southwest Hokkaido (photo: Yasuhito Uchida)

We conducted offshore active fault survey at the southern part of the eastern marginal fault zone of the Ishikari lowland. The fault zone comprises east-dipping blind reverse faults and their fault-related folds. To investigate and characterize activity of the fault, we obtained sedimentary cores using the vibro-corer. Photo (top) shows the vibro-corer entering the sea, suspended by the survey-ship crane. Photo (bottom) shows the vibrocorer on the deck of the ship. The vibro-corer can penetrate sea-bottom coarse sediment up to 6 m long owing to the vibration generator. See the detail in Uchida et al. on pages 1-36.