Fig. 1

a Sketch of the experimental setup (modified from Griffiths et al. 2018) for wave velocity measurements on a Westerly Granite sample. The apparatus consists of a uniaxial press, a tube furnace and for waveform measurements, a pair of high temperature resistant and broadband acoustic sensors that are set in direct contact with opposing ends of the sample [see Griffiths et al. (2018) for details]. Upper acoustic sensor is the source and the lower one is the receiver. b Evolution with time during three heating/cooling cycles, of the temperature measured at the center of the sample with a thermocouple inserted into a hole drilled radially