Seismo-turbidites in the Japan Trench inner slope
Thursday, 18 December 2014
The Japan Trench is a part of the Pacific-North America plate boundary, and is a seismically active region where the 2011 off the Pacific coast of Tohoku Earthquake occurred. We collected 24 piston cores from small basins of the Japan Trench inner slope (37.5-40 N, 143.5-144.16 E, 4000-6000 m in water depth) during the cruise NT13-19 with R/V Natsushima, to investigate recurrence intervals of earthquakes in this area, based on the analysis of the turbidite record. Many fine-grained turbidites are observed in the cores. High sedimentation rates in this area preserve the turbidites well. Turbidites are more frequently intercalated in the cores recovered from the southern part of the area. On the other hand, several turbidite layers can be correlated widely in the northern part of the area, assisted by tephrostratigraphy and matching of paleomagnetic secular variations. Moreover, some of these turbidites are considered to be correlative to the reported onshore tsunami deposits along the Sanriku-Sendai coast. We will report the occurrence, characteristics and correlation of seismo-turbidites in the Japan Trench inner slope. The evidence suggests that the Japan Trench area is an ideal site for application of turbidite paleoseismology.