Figure 2.

CT scan image of the Beppu Bay sediments and Pu measurements using Accelerator Mass Spectrometer (AMS). Horizons of geological event layers (e.g., Ev-1e, Ev-1dU etc.) can be recognized in images of cores and are traceable amongst cores taken from the basin²⁴. They are formed by turbidite created from Tsunamis and other events. Ev.-1a at 46.0 cm bsf is recorded in historical documents with an age consistent with the Pb-210 age model. Pu isotope ratios and total activities are measured using Accelerator Mass Spectrometry⁶³.