[S-CG48] 海洋底地球科学

[SCG48-P19] タービダイトを使った千島海溝斜面の古地震学

*熊 衎昕¹、金松 敏也¹、中西 諒² (1.国立研究開発法人海洋研究開発機構、2.京都大学)

キーワード：古地震学、タービダイト、火山灰、古地磁気永年変化、千島海溝

Large earthquakes have been frequently occurred along the southern Kuril Trench, eastern Hokkaido, Japan, where the Pacific Plate is subducting beneath the overriding North American Plate. This region is pivotal for paleoseismological studies due to its high seismic activity and destructive earthquakes. Deep-sea turbidites offer a valuable window into past earthquake events, aiding our comprehension of earthquake cycles and facilitating risk mitigation. During the KS19-12 cruise, two piston cores, PC01 and PC02, were obtained from a submarine fan on the lower Kuril Trench slope, north of the Kushiro Canyon. Water Depths are 3324 meters of PC01 and 3734 meters of PC02, with PC02 located 36.5 km southwest of PC01. An 8 m-long piston coring system with 7.8 cm-diameter core liners was used to collect piston cores PC01 and PC02, with PC01 measuring 5.16 m in length and PC02 measuring 5.33 m. Lithology revealed that these cores primarily consist of dark grayish-yellow silt with thin-bedded coarser layers of fine sand, identified as turbidites. Age models, employing methods such as volcanic ashes, Paleomagnetic Secular Variation, ¹⁴C from bulk organic carbon, and ¹⁴C dating from foraminifera, were established for the cores. The age model provides constraints on event ages and sedimentation rates. These preliminary findings significantly contribute to our understanding of turbidite reoccurrences for paleoseismology and sedimentation patterns in the Kuril Trench slope.