Observed and calculated heat flow in the southern and northern regions. Thermal structure is calculated with 2 and 6 cm/year convergence rate for southern and northern regions, respectively. Three values of frictional parameter (λ =0.94, 0.96, and 0.98) are tested in each region, which are represented by blue, red, and green lines, respectively. Triangles indicate observed heat flow values. Heat flow values observed at regions in the southwestward and northeastward strike direction from the brown line in Figure 1 are shown in South and North panel, respectively. Shaded area represents the volcanic region, which is not considered in our model, and offshore region, where the observed heat flow data have large uncertainty. Two orange-colored rectangles and a magenta-colored rectangle show the mean and standard deviation values of observed heat flow data at southern, northern, and northernmost onshore coastal region, respectively (Figure 1).