Data report: rate- and state-dependent friction parameters of core samples from Site C0019, IODP Expedition 343 (JFAST)

Abstract

This report explains shearing tests conducted on samples collected throughout the main cored interval at Site C0019 during Integrated Ocean Drilling Program Expedition 343, the Japan Trench Fast Drilling Project. This site is located within the region of high coseismic slip during the 2011 Tohoku earthquake that reached the ocean floor at the Japan Trench. Results of velocity-stepping tests within 0.1-30 µm/s on both intact and powdered samples allowed quantification of the rate- and state-dependent friction constitutive parameters a-b, a, b1, b2, Dc1 and Dc2 by inverse modeling techniques. Also reported here are measurements of the initial friction prior to each step (µo) and the slip-dependence of friction (η), which were used as input parameters to the model. Downhole patterns of friction parameters are observed to correlate consistently with lithology. For powdered samples, the fault zone, a siliceous mudstone ∼2 m below the fault zone, and three pelagic clay samples can be distinguished from hanging wall and underthrust footwall siliceous mudstones by lower a, lower b, higher a-b. These results indicate a tendency for velocity strengthening, lower friction, and higher ν, which indicates a tendency for slip-hardening. Intact samples show the same patterns, albeit with fewer data points. Aside from the lithologic control, strong downhole trends in the friction parameters are not observed.