Fig. 4

Estimated stress field in the eastern margin of the Japan Sea (EMJS). \({\upphi }_{{\text{best}}}\) is the optimal value of the stress ratio (\(\phi (={\sigma }_{2}-{\sigma }_{3})/({\sigma }_{1}-{\sigma }_{3})\)) with a 95% confidence range of \(\phi\). \({{\text{S}}}_{{\text{Hmax}}}\) is the maximum horizontal compressional direction. \({{\text{N}}}_{{\text{a}}}\) is the number of focal mechanisms used for each stress inversion in each area. The numbers in the upper left correspond to the subareas identified in Fig. 3