Fig. 10

Schematic depth distribution of stress due to a deep heat source. Close-up of the central vertical plane (blue rectangle) is shown to the left of each figure. a If a rock block is located above a heat source, and the block can be freely deformed, the bottom half of the block will expand due to heating. In this case, horizontal deviatoric strain is contraction in the shallower part and dilatation in the lower part as indicated by green arrows. Note that this strain is not the elastic strain but the thermal one causing no stress change. b In the crust, however, the block cannot be freely deformed, but becomes locked at each end. Horizontal deviatoric stress becomes compressional in the bottom half and tensional in the top half as indicated by purple arrows. Note that the vertical deviatoric strain and stress are not plotted in the figure, for the sake of simplicity. Here we presume that hot water or partial melt is acting as a heat source as proposed by Yoshida et al. (2011) and Kato et al. (2014)