QuakeCycles: Earthquake supercycles in the Japan Trench?

Japan is located on the Pacific Ring of Fire, a region of special interest in earthquake research. It is here that oceanic plates bend and move below overriding plates, while accumulating long-term global plate tectonic strain. This energy is released cataclysmically during so-called subduction zone or megathrust earthquakes. These high impact earthquakes and associated tsunamis such as the Tohoku-oki Earthquake and Tsunami in Japan in 2011 are major geological events with a high impact on society and infrastructure and represent the greatest hazard for coastal societies in the Pacific region. Giant earthquakes such as these are likely to happen again, but instrumental and historic records of these events are currently insufficient to adequately assess seismic and tsunami hazards in areas located close to subduction plate boundaries. The goal of the FWF-QuakeCycle-Japan project is now to gain an improved perspective of earthquake maximum magnitudes and recurrence. For this purpose, cores from the Japan Trench, which were recovered by International Ocean Discovery Program (IODP) Expedition 386 "Japan Trench Paleoseismology", will be analyzed to unravel the long-term history of this giant earthquake- producing plate boundary system. Strong offshore earthquakes affect marine sediments and leave records of their occurrence in the sub-seafloor. The ultra-deep water sedimentary basins of the Japan Trench comprise the terminal sink of earthquake-triggered sediment remobilization, thus providing excellent and continuous archives of past earthquake occurrences. These sediment archives are like ultra-deep-water seismograph that have been recording major earthquake events over time periods extending several tens of thousands of years into the past. The most recent giant 2011 Tohoku-oki Earthquake and older megathrust earthquakes documented in Japanese written history allow for calibration of this natural seismograph to unravel this sedimentary deep-time archive of past earthquakes. By doing so, the FWF-QuakeCycle-Japan research team will document the temporal and spatial distribution of past earthquake occurrences along the entire Japan Trench Subduction zone, including different earthquake rupture segments that may or may not have ruptured in one giant or several great earthquakes, respectively. This will deliver unprecedented long-term observational data to test two fundament hypotheses of earthquake research by statistically robust paleoseismic recurrence data: (1) strong megathrust earthquakes occur in supercycles; (2) the maximum size of giant earthquakes is controlled by structurally-controlled long- term persistent rupture boundaries.