The movement of rotational and translational landslides occurs as a result of either sliding on discrete shear surfaces or ductile deformation within a shear zone. In this paper we examine the movement histories of a number of landslides that occurred in a variety of materials in a range of settings, and demonstrate that one of two movement styles is evident during accelerating phases for all landslides observed. The first style, which has previously been noted, has a linear form in a plot of 1/v against time (v is velocity). The second style has an asymptotic form in the same plot, trending toward steady-state movement rates. We propose that the linear form occurs in landslides in which crack propagation (i.e., shear surface generation) is the dominant process, whereas the second style occurs where movement is taking place across existing planes of weakness or as a result of ductile deformation processes. This study demonstrates that the evaluation of plots of 1/v against time for landslides is a useful technique for forecasting movement styles and rates, and for interpreting ongoing deformation processes in real time.

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