Before revision:  These are characterized by the fact that the unrest has respectively a negative or positive feedback on the social tension (though no monotonicity condition is assumed). In 17 we derive a threshold phenomenon in terms of the initial level of social tension: below a critical value, a small triggering event is quickly followed by a resumption of calm, while, above this value, it generates an eruption of social unrest spreading through space with an asymptotically constant speed.
After revision:  These are characterized by the fact that the unrest has respectively a negative or 17 we derive a threshold phenomenon in terms of the initial level of social tension: below a critical value, a small triggering event is quickly followed by a resumption of calm, while, above this value, it generates an eruption of social unrest spreading through space with an asymptotically constant speed.