1. Animated sequences: Videos of dynamic fracture propagation in four examples of experiments There are four examples (A, B, C, D) of experiments presented in the next slides. For each experiment TWO videos are presented on the same slide, - the one obtained with the “cumulative” image processing - the one obtained with the “dynamic” image processing (processing is described in the supplementary information pdf document). Cumulative videos are indicative of stress change cumulated since the beginning of nucleation. Dynamic videos, instead, only indicate the variation between one image and the next, and thus enhance the visibility of waves and dynamic stress perturbations. For experiment A and B, a static sequence of gathered snapshots is also shown for both “dynamic” and “cumulative” images. For experiment D, only the “dynamic” snapshot gather is shown (splitted in two successive panels).

2. Explanation of the geometry in the animated snapshots:

3. The following two experiments, “crack 001” and “crack 014”, are done on smooth clean surface. The two examples show rupture expanding bilaterally from an initial nucleation patch. The nucleation can be seen in the “cumulative” videos: it extends between the two visible stress perturbation regions in proximity of the fracture extremities.

4. Dynamic Cumulative Example A - “crack 001” (bilateral rupture nucleation and propagation on smooth surface) Frame rate: 100k fps; video duration: 0.72 ms 50 mm

5. Example A - “crack 001” Cumulative Dynamic 0  s sample edges 154.3 mm 250  s 500  s

6. Example B - “crack 014” (bilateral rupture nucleation and propagation on smooth surface) Dynamic Cumulative Frame rate: 100k fps; video duration: 0.32 ms 50 mm

7. Example B - “crack 014” Cumulative Dynamic 0  s 100  s 200  s 300  s

8. Experiments “crack 173” and “crack 179” are performed on rougher sliding surfaces. They show complexity (in particular ”crack 179”) in the form of multiple rupturing, stop and start sequences, deceleration-acceleration of rupture and aftershocks, within a short time interval.

9. Example C - “crack 173” (unilateral double rupture sequence on rough surface) Dynamic Cumulative Frame rate: 100k fps; video duration: 1.46 ms 50 mm

10. Example D - “crack 179” (complex, multiple rupture sequence on rough surface) Dynamic Cumulative Frame rate: 100k fps; video duration: 1.75 ms 50 mm

11. Example D - “crack 179” Dynamic lubricant patches 0  s 250  s 500  s 750  s 1000  s 1250  s