Keishi Okazaki and Greg Hirth present deformation and acoustic emission measurements on the silicate mineral lawsonite, designed to test whether the lawsonite dehydration reaction can induce unstable fault slip that might explain the source of intermediate-depth earthquakes in cold subduction zones. The results show that unstable fault slip (or stick-slip) does occur in lawsonite during dehydration reactions. Acoustic emission signals were continuously observed, indicating the potential for unstable frictional sliding within natural lawsonite layers. This behaviour is in direct contrast to similar experiments on the serpentine mineral antigorite, which show stable or slow slip and no acoustic emission during dehydration in similar conditions. This work demonstrates that lawsonite is one of the few minerals that exhibit brittle deformation resulting in unstable fault slip at high pressure and temperature.
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