Fig. 6
Strength profile for the past North Pole every 1 billion years. The rheological structure of the past North Pole was predicted from the temperature profile (Fig. 4a). Strength in the brittle deformation region was calculated by using Byerlee’s law (Byerlee 1978). In the region of ductile deformation, the Peierls mechanism, power-law creep, and diffusion creep (grain boundary diffusion) were applied to calculate the strength at each depth, as shown in Fig. 5. The strain rate was assumed to be 10−14 (solid line) or 10−16 s−1 (dashed line). The parameters used are summarized in Table 3; the rheological structure for both dry (red lines) and wet (blue lines) rheologies is shown. The dashed line labeled SAF shows the frictional strength of the San Andreas Fault, for which µ = 0.15 (Lockner et al. 2011)