Radioisotopic Analyses of Sediment Cores from the Japan Margin Trench

The samples were collected from the R/V Natsushima 13-02 and 13-19 from the Japan Trench slope and Mid-Slope terrace for studying earthquake genereated turbidites. The focus was on the 2011 Mw9.0 Tohoku earthquake and tsunami. Radionuclide measurements were carried out using a gamma counter with a germanium detector operated in the “well” configuration (ORTEC GWL-120) at the laboratory of Dr. Bopp at Rensselaer Polytechnic Institute. Blank corrections were applied to each sample based on the analysis of empty sample containers. Background corrections were applied to each radionuclide based on the sample count rate at energies just above and just below each peak of interest. Detector efficiency was calibrated using an NBS sediment standard (River sediment NBS 4350B), a liquid NBS standard (NBS 4953-C) that was used to prepare spiked sediments (G-standards), and secondary standards (D-standards) prepared at LDEO and calibrated to NBS standards. Certified reference material supplied by the National Institute of Metrology, Beijing, China (River sediment GBW08304a) and a secondary standard (LGP) analyzed for 210Pb(tot) by alpha spectrometry at the LDEO were also used as standards. The samples were analyzed for 137Cs, 7Be, 234Th, and excess 210Pb using procedures by Bopp et al. (2006).