Fig. 4
From: Spatial heterogeneities in tectonic stress in Kyushu, Japan and their relation to a major shear zone
Principal stress directions at the spatial grid within the 95 % confidence range by the bootstrap test. a and b are the western and eastern parts of Kyushu. The direction is plotted on the lower hemisphere. The optimum stress field at each grid is shown as a focal mechanism plot. Blue, green, and red dots indicate σ 1, σ 2, and σ 3, respectively. Each “beach ball” location corresponds to a spatial grid-point distribution on the map at the center of the figure. The map shows a part of Fig. 3a