Fig. 8

a P-wave velocity as a function of bulk density. Grey triangles are data for Permo-Triassic sandstones from the EPS-1 exploratory borehole at Soultz-sous-Forêts, France (Heap et al. 2017); Grey squares are data for granites from the GPK-1 borehole at Soultz-sous-Forêts, France (Rummel 1992). Each square is the average value for a given depth and the error bars give the standard deviation. b Permeability as a function of connected porosity. We compare the data gathered in this study with data for the Permo-Triassic sandstones (Griffiths et al. 2016; Heap et al. 2017) and granites (Géraud et al. 2010) from the EPS-1 exploratory borehole at Soultz-sous-Forêts, France. c Uniaxial compressive strength of the sedimentary rocks investigated in the present study. Black curves—the analytical approximation of the pore-emanating crack model, as derived by Zhu et al. (2010). d Elastic modulus of the rocks investigated in the present study. The rocks from this study are categorised as either being sedimentary (red squares), from the crystalline basement (blue triangles), or as being other lithologies (black circles); see Table 2