Active Fault and Paleoearthquake Researches No. 12 (2012)

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Top: Paleoseismic trench survey at Goda site on the middle section of the Itoigawa-Shizuoka Tectonic Line active fault system, central Japan

Paleoseismic trench survey at Goda site on the middle section of the Itoigawa-Shizuoka Tectonic Line active fault system, central Japan. We excavated a single trench across a 4-m-high fault scarp in order to reconstruct paleoseismic history of the Okaya fault. On the trench walls, several faults cut alluvium composed of fine and peaty sediments, and fluvial terrace deposits. As a preliminary result, we reconstructed four paleoearthquake events during the last 7200 years.

Bottom: High-resolution multichannel profile in the offshore extension of the Gomura fault zone (Line TG9 SP1-1600)

Top: Time section, Bottom: Geological interpretation.