2:30 PM - 2:45 PM
[HCG23-04] The isotopic signature of remobilized sediment by Tohoku 2011 and prior earthquakes: Japan trench and slope
Keywords:Japan Trench margin, 2011 Tohoku-oki earthquake, remobilized sediment, short-lived radioisotopes, Sr. Pb, epsilon Nd isotopes, paleoearthquakes
Short-lived radioisotopes identify sediment associated with the Tohoku 2011 Mw9, which is characterized for its thickness and spatial distribution from 600 to 8000 m of water depth. In the southernmost basin of the Japan Trench, an ~2m thick homogeneous deposit was linked to the 2011 earthquake. Similar, up to 7m thick homogeneous deposits that likely resulted from M9 paleoearthquakes, were documented in other trench cores. Sr, Nd and Pb isotopic ratios reveal a shift to more mantle like values, most likely because arc materials are concentrated in these homogeneous deposits. In contrast, the isotopic signal of smaller, younger and older turbidites, has a more negative epsilon Nd and more radiogenic Sr, consistent with an older continental crust. These new findings derived from turbidites recovered from the Japan Trench indicate that there is along trench and downcore variability in isotope ratios. This variability has the potential to identify sediment sources and along-strike extent of historic and prehistoric ruptures.