The marine-geological fingerprint of the 2011 Magnitude 9 Tohoku-oki earthquake

Abstract:

The 2011 Tohoku-oki earthquake was the first great subduction zone earthquake, for which the entire activity was recorded by offshore geophysical, seismological and geodetic instruments and for which direct observation for sediment re-suspension and re-deposition was documented across the entire margin. Furthermore, the resulting tsunami and subsequent tragic incident at Fukushima nuclear power station, has induced short-lived radionuclides which can be used for tracer experiments in the natural offshore sedimentary systems.

Here we present a summary on the present knowledge on the 2011 event beds in the offshore environment and integrate data from offshore instruments with sedimentological, geochemical and physical property data on core samples to report various types of event deposits resulting from earthquake-triggered submarine landslides, downslope sediment transport by turbidity currents, surficial sediment remobilization from the agitation and resuspension of unconsolidated surface sediments by the earthquake ground motion, as well as tsunami-induced sediment transport from shallow waters to the deep sea. The rapidly growing data set from offshore Tohoku further allows for discussion about (i) what we can learn from this well-documented event for general submarine paleoseismology aspects and (ii) potential of the Japan Trench to use the geological record of the Japan Trench to reconstruct a long-term history of great subduction zone earthquakes.