Examples of interarrival time histograms of two real-world news events discussed on Twitter.

The event [nelson, mandela] (top) was collected on 12/05/2013. Since there is a high concentration in the first histogram bin, we conclude that most of the social media posts for this event occur in one or more successions of high-activity bursts (therefore, considered a high-activity event). The second event, [may, oscar] (bottom) was collected on 03/23/2014 about The Oscars event that was held a few weeks before. The arrival times of these posts are much more spread out, displaying much less concentration of bursty activity.