- 1RWTH Aachen University, Institute for Neotectonics and Natural Hazards, Aachen, Germany (p.bellanova@nug.rwth-aachen.de)
- 2Department of Science and High Technology, Università degli Studi dell'Insubria, Como, Italy
- 3IFREMER, Géosciences Marines, Plouzané, France
- 4Boone Pickens School of Geology, Oklahoma State University, Stillwater, OK, USA
- 5Institute for Geosciences, University of Bonn, Bonn, Germany
- 6Stony Brook University, Department of Geosciences; New York, USA
- 7MARUM – Center for Marine Environmental Science, University of Bremen; Bremen, Germany
- 8Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China; Qingdao, China
- 9Laboratory for Marine Geology, Qingdao Marine Science and Technology Center, Qingdao, China
- 10Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University; Shanghai, China
- 11Department of Geology, University of Innsbruck, Innsbruck, Austria
- 12AIST Geological Survey of Japan, Research Institute of Geology and Geoinformation, Japan
The 2011 Tohoku-Oki earthquake highlighted substantial deficiencies in our understanding and an underestimation of the hazard potential of megathrust earthquakes and their cascading effects, including tsunamis. Offshore deep-sea paleoseismology evolved from the need to better understand mechanisms and depositional processes within megathrust subduction zones. The examination of sedimentary records has demonstrated effectiveness in reconstructing complex historical seismic events resulting in multi-pulse depositional sequences. However, reliably identifying individual turbidite sequences and delineating precise boundaries of distinct events remains challenging. This is especially true for the upper limit of turbidite-homogenite sequences where the contact between the homogenite and the background sedimentation is gradual and visually not detectable. Advances in organic geochemistry (e.g., high-resolution GC-MS and lower detection limits) can overcome and push such limitations. Organic sedimentary biomarkers, such as n-alkanes, polycyclic aromatic hydrocarbons, and fatty acids, serve as robust proxies for identifying allochthonous, earthquake-related strata and differentiating them from (hemi-)pelagic deposits. The high source-specificity of sedimentary biomarkers allows for obtaining sediment provenance information and the reconstruction of transport processes and depositional history.
In the Japan Trench, hadal seismic sediments result from turbidity currents transferring substantial amounts of material from shallow marine and coastal regions (e.g., tsunami backwash) into deep hadal basins. Initial sedimentary biomarker results from n-alkanes, steranes, and hopanes present a distinct marine signature from planktonic sources for the background sediments. However, turbidites and homogenite deposits linked to seismic events present increases in terrigenous signals, suggesting input of remobilized material from shallower marine environments or through a tsunami backwash.
This study highlights the application of organic sedimentary biomarkers as proxies to identify, characterize, and reconstruct past megathrust earthquakes (MW≥9) in the Japan Trench. By bridging current knowledge gaps, this approach advances seismic hazard assessment and supports the future development of improved mitigation strategies through an enhanced understanding of paleoseismological records.
How to cite: Bellanova, P., Trotta, S., Brunet, M., Riedinger, N., März, C., Rasbury, T., Koelling, M., Bao, R., Luo, M., Strasser, M., Ikehara, K., and Reicherter, K.: Identifying tsunamigenic megathrust events in the Japan Trench through sedimentary biomarkers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18629, https://doi.org/10.5194/egusphere-egu25-18629, 2025.
