Fig. 5

CT images showing the relationship between spatial heterogeneity in the ultramylonite sample and AE events in the initial stage of fracture development, between 12,600 and 12,700 s (Fig. 3g). a Fracturing initiated a short distance from the preexisting damage plane in a heterogeneous region (within the yellow oval). The dashed red line indicates the preexisting healed plane. b Relationship of AE events during the earliest stage of fracture development (red dots) to later zones of failure (plotted on the same image as that in Fig. 4a)