Large Earthquakes Recorded as Deep-sea Turbidities in the Rishiri Trough, Northernmost Hokkaido

摘要

Two turbidite layers of earthquake origin were found in a sediment core collected from the Rishiri Trough, west of Rebun Island, northernmost part of Hokkaido, Japan. Radi- ocarbon age determinations using planktonic foraminiferal tests in hemipelagic mud in- dicated that the depositional ages of each turbidite were 2,300 ~14C yrs BP and 5,500 ~14C yrs BP, respectively. Therefore, the recurrence interval of the large earthquakes forming the turbidites in this area was estimated to be around 3,200 years.