Figure 2
Crustal stresses in the Philippine Sea slab beneath the Shikoku district and the Kii Peninsula. (a) Lower-hemisphere equal-area stereographic projections showing the results of the multiple inverse method7 applied to data from the 188-point dataset of Fig. 1, and the results of the k-means clustering31 applied to the data. Diamonds and squares indicate σ1- and σ3-axes, respectively. The colour of the symbols represents the stress ratio. Dashed circles show 95% confidence intervals of the stresses. (b) Analysis of dimensionless Mohr diagrams obtained for the Philippine Sea slab beneath the Shikoku district and the Kii Peninsula. The lower boundary of the mass of representative points is shown as a broken line. We classified 36 earthquake events into three groups as F1, F2, and F3 to estimate the effective friction coefficient μ′ for each fault group compatible only with the stress. We used a value of 0.6 for the friction coefficient μ16.
