Fig. 12

Conceptual diagram of the stress field proposed in this study. The stress field in this study area can be explained by a combination of local thermal stress and regional tectonic stress. Focal mechanisms are controlled by weak planes such as geological faults under the stress regime shown here. Earthquakes hardly occur at the shallowest depths (z ≤ 2 km) because the normal stresses on the faults are too small. Therefore, the tensional stress field just beneath the surface is not likely to resolve in a stress inversion that uses focal mechanisms. For this reason, we labeled “unresolved” for the expected stress field in the shallowest part