Steady-state friction coefficient plotted against the logarithm of slip velocity. Blue and red circles show the data determined in this study using samples from DSDP Site 436. Yellow triangles are the data obtained through rotary shear experiments on the plate boundary fault collected at the Japan Trench (Expedition 343; Site C0019), reported in Ujiie et al. (2013). Other symbols are experimental results obtained by rotary shear experiments on sediments that occur around faults in the Nankai Trough (Expedition 316; Sites C0004D and C0007D), from Ujiie and Tsutsumi (2010), Tsutsumi et al. (2011), and Hirose et al. (2008), shown for comparison.