Japan Trench Outer-Rise Paleoseismology

• Applicant: Dr. Piero Bellanova
• Subject Area: Geology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565848016

Since the 2011 Tohoku-Oki earthquake (MW 9.0) mainshock, several MW >7 earthquakes on the outer-rise of the Japan Trench have been instrumentally recorded with varying depths and spatial locations. Yet, the Japan Trench outer-rise remains poorly known as the incoming Pacific plate has rarely been targeted by scientific ocean drilling. While the outer-rise is known to cause tsunamigenic seismicity (e.g., 1933 CE Shōwa Sanriku-Oki tsunami), it has never been targeted for paleoseismological research. Terminal sedimentary sinks in (semi-)enclosed basins of the abyssal and hadal zones of the Japan Trench’s outer-rise offer long-term archives recording past seismic multi-pulse megathrust cycles. This project sets out to advance our understanding of paleoseismicity and tsunamigenic hazards in subduction zones, particularly along the Japan Trench outer-rise. The primary objectives are to (I) identify earthquake-driven sediment sequences and distinguish them from the hemipelagic background sedimentation; (II) explore paleoseismic sedimentary transport and depositional processes and determine sediment provenance; and (III) develop a long-term record of earthquake cycles on the outer-rise. By combining a sedimentological and biogeochemical approach, it is aimed at distinguishing the (hemi-)pelagic background sedimentation from seismic deposits, namely turbidite-homogenite sequences and sedimentary features (e.g., sediment-filled veins). Therefore, this project leverages recent breakthroughs from International Ocean Discovery Program (IODP) Expedition 405, which recovered deep-sea sediment cores from the Japan Trench to study earthquake-triggered sedimentary processes and their long-term records. The Japan Trench offers a natural laboratory for advancing our understanding of subduction zone processes, seismic hazard assessment, and the interplay between tectonic mechanics, earthquake generation, and co-seismic sedimentary and sediment-transport processes. Preliminary findings reveal a remarkable record of at least 70 potential turbidites and 15 sediment-filled veins within the top 100 meters below the seafloor of the Japan Trench’s outer-rise, offering unprecedented insights into past seismic events. The outer trench swells are geoscientific frontiers, and much remains to be learned about them. Thus, the scientific community has an obligation to learn as much as possible from this unique opportunity to study the first paleoseismic record, fundamental mechanisms, and tsunamigenic and seismic hazard potential of a subduction zone’s outer-rise. The outcomes will enhance hazard models and seismic risk assessments, benefiting coastal communities vulnerable to future megathrust earthquakes.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 527: Infrastructure area - International Ocean Drilling Programme³ (IODP³)
• International Connection: Canada
• Cooperation Partner: Dr. Morgane Brunet