Fig. 5

Depth distribution of the relocated hypocenters in pelitic rocks (light blue histogram; region a in Fig. 4) and mafic rocks (green histogram; region b in Fig. 4). The histograms are created using the relocated hypocenters within the rectangles labelled ‘a’ and ‘b’ in Fig. 4a. The light blue and green bars on the right side of the figure indicate the temperature ranges, where the pelitic and mafic rocks show velocity-weakening properties, respectively, as inferred from petrological experiments. The black bars in the background indicate the temperature ranges of the experiments. The light blue and green triangles indicate the temperatures that cause the greatest degree of velocity-weakening (i.e., when the friction rate parameter, a–b, is at a minimum)