Sediment Shear Strength Development Within Terminal Basins of the Japan Trench and Lower Slope: Insights Into Seismic Strengthening and Earthquake Paleoseismology From R/V Sonne Expedition SO251 (Eager-Japan) and IODP Expedition 386
Description:
Recent findings have demonstrated that the Quaternary sedimentary fill in hadal basins along the Japan Trench, consists of two distinct deposition styles: slow background deposition punctuated with rapid event beds of variable thickness. In this study, we examine this bimodal basin fill pattern to investigate shear strength and how shear strength changes over time during burial and exposure to seismic activity. We compare strength profiles of basin sediment to sites located on the lower slope where sedimentation is expected to be low and prone to sediment bypass, erosion, and seismic strengthening. We compile shear strength data from R/V Sonne Expedition SO251 (EAGER-JAPAN) that acquired piston cores in the basins and the slope, and IODP Expedition 386 that acquired 29 giant piston cores in 15 basin sites. We find: 2 distinct shear strength profiles: sediments in the deep basins have low-to-normal shear strengths while sites on the slope have anomalously high shear strengths. A further finding in the basin sites is that the shear strength profiles of thick near-seafloor acoustically transparent units in subbottom data have lower-than-normal shear strengths. We interpret: the low-to-normal basin strengths are likely representative of relatively high sedimentation rates including raid, episodic pulses of sediment from earthquake-triggered event beds. Further, in young event beds that are still undergoing consolidation, this may be used as a novel way to constrain age of the event bed to complement traditional age-dating techniques. In contrast, slope sites may be prone to a combination of erosion and seismic strengthening, leaving sediments strengthened.
Session: From Faults to Fjords: Earthquake Evidence in Terrestrial and Subaqueous Environments - II
Type: Oral
Date: 5/1/2024
Presentation Time: 11:15 AM (local time)
Presenting Author: Derek
Student Presenter: No
Invited Presentation:
Authors
Derek Sawyer Presenting Author Corresponding Author sawyer.144@osu.edu Ohio State University |
Michael Strasser michael.strasser@uibk.ac.at University of Innsbruck |
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Sediment Shear Strength Development Within Terminal Basins of the Japan Trench and Lower Slope: Insights Into Seismic Strengthening and Earthquake Paleoseismology From R/V Sonne Expedition SO251 (Eager-Japan) and IODP Expedition 386
Category
From Faults to Fjords: Earthquake Evidence in Terrestrial and Subaqueous Environments